Answer:
0.1 moles
Explanation:
Okay, the explanation here is pretty long. Let’s go!
Firstly, we know that the compound contains only carbon, hydrogen, oxygen and nitrogen. So the molecular formula would look like this CxHyOzNp
Where x , y, z and p are number of atoms of each element present respectively. According to the law of constant composition, the ratio of the number of atoms are fixed irrespective of the source or method of preparation. From this, we now know that in both samples, we have the same number of atoms. What is proper to do is to calculate the numbers, we do that as follows.
Firstly, we will need to calculate these numbers using the masses given in the first sample. Over the calculations, we should note that the formula we would be using is the relation: mass = number of moles * atomic mass or molar mass. Rearranging the equation gives different variations of the formula.
Now let’s do some mathematics.
There is 3.94g of carbon iv oxide, we can calculate the number of moles of it present which eventually would yield the number of moles of carbon present.
The molar mass of carbon iv oxide is 44g/mol.
The number of moles of carbon iv oxide present is thus 3.94/44 = 0.0895 moles
Since there is just 1 atom of carbon present in carbon iv oxide, this means the number of moles of carbon present is also 0.0895 moles
The mass of carbon present is the number of moles of it present multiplied by the atomic mass unit of carbon which is 12. This mass is 0.0895 * 12 = 1.0745g
Next, we calculate the number of moles of hydrogen and consequently its mass present.
To get this, we can access it from the number of moles of water present.
We get this by dividing the mass of water present by the molar mass of water. This is equals 1.89/18 = 0.105 moles. Now we know that 1 mole of water has 2 atoms of hydrogen, hence 1 mole of water will yield 2 moles of hydrogen. The number of moles of hydrogen present is thus 0.105 * 2 = 0.21 moles.
The mass of hydrogen thus present is 0.21 * 1 = 0.21g
Now, we know the mass of hydrogen present and the mass of carbon present. But, we do not know the mass of oxygen and nitrogen present.
To get this, we subtract the mass of hydrogen and carbon present from the mass of the total= 2.18 - 1.0745 - 0.21 = 0.8955g
Now we know the mass of oxygen and nitrogen combined. We can access their number of moles using their respective atomic masses. The total number of moles present is equal 0.8955/30 = 0.02985 moles
Wondering where 30 came from? The atomic mass of nitrogen and oxygen are 14 and 16 respectively. We now get the number of moles of both present. This is equal to the atomic mass divided by the total mass multiplied by the number of moles.
For oxygen = 16/30 * 0.02985 = 0.01592
For nitrogen = 14/30 * 0.02985 = 0.01393
From this we can try and get an empirical formula for the compound. This helps us to know the ratios of the number of atoms. To get this , we divide the number of moles by the smallest number of moles. The smallest number of moles is unarguably that of nitrogen. The empirical formula is calculated as follows:
C = 0.0895/0.01393 = 6
H = 0.21/0.01393 = 15
O = 0.01592/0.01393 = 1
N = 0.01393/0.01393 = 1
Thus, the empirical formula looks like this :
C6H15NO
Now, we can move to the second sample.
We know that the sample contains 0.235g of nitrogen. We first need to get the number of moles of nitrogen present in the sample. To get this, we simply divide this mass by the atomic mass. That is: 0.235/14 = 0.0168 moles
Now since the question asks us to get the number of moles of carbon and we know that in any elemental analysis, the ratio of carbon to nitrogen is 6 to 1, we simply multiply the number of moles of nitrogen by 6.
Hence, this is 0.0168 * 6 = 0.1 moles
Final answer:
The moles of carbon in the sample can be calculated using the mass of CO2 produced during combustion. The calculated moles of carbon are 0.0895 mol, based on the provided mass of CO2 and its molar mass.
Explanation:
The question asks how to calculate the moles of carbon in a sample based on combustion analysis data. To find the moles of carbon, we use the mass of CO2 produced during combustion. Since each mole of CO2 contains one mole of carbon, the moles of CO2 will equal the moles of carbon. The mass of CO2 produced is 3.94 g. The molar mass of CO2 is 44.01 g/mol.
Using the formula moles = mass / molar mass, the moles of carbon can be calculated as:
Moles of C = 3.94 g CO2 / 44.01 g/mol = 0.0895 mol C
This calculation determines the amount of carbon present in the sample by analyzing the carbon dioxide produced during combustion.
What volume of carbon dioxide is produced when 0.489 mol of calcium carbonate reacts completely according to the following reaction at 0°C and 1 atm? calcium carbonate ( s ) calcium oxide ( s ) + carbon dioxide ( g )
Answer:
11.0L of carbon dioxide is produced
Explanation:
Balanced equation: [tex]CaCO_{3}(s)\rightarrow CaO(s)+CO_{2}(g)[/tex]
According to balanced equation, 1 mol of [tex]CaCO_{3}[/tex] produces 1 mol of [tex]CO_{2}[/tex]
So, 0.489 mol of [tex]CaCO_{3}[/tex] produces 0.489 mol of [tex]CO_{2}[/tex]
Let's assume [tex]CO_{2}[/tex] behaves ideally.
So, [tex]P_{CO_{2}}V_{CO_{2}}=n_{CO_{2}}RT[/tex]
where P is pressure, V is volume , n is number of moles, R is gas constant and T is temperature in kelvin
Plug-in all the values in the above equation-
[tex](1atm)\times V_{CO_{2}}=(0.489mol)\times (0.0821L.atm.mol^{-1}.K^{-1})\times (273K)[/tex]
or, [tex]V_{CO_{2}}=11.0L[/tex]
So, 11.0L of carbon dioxide is produced
If the forces acting on an object are unbalanced, what will occur?
Constant speed
Change in mass
Constant velocity
Acceleration
Answer:
The answer is acceleration.
Explanation:
Acceleration- When it comes to science, Force is defined as a "push or pull" of an object with mass that causes it to change velocity.
Balanced Force- This occurs when two forces of the same mass or size are acting on a particular object in opposite direction. The object being acted upon could either stay in its place or move in a uniform speed and direction.
Unbalanced Force- This occurs when the forces applied are not equal and are of different direction. For example, a 55-kg person pulling a 30-kg cart. The cart will move to the direction of the pull.
Thus, when forces acting on an object are unbalanced, it causes the object to accelerate. This acceleration is directly proportional to the "net force", but is inversely proportional to the mass or size.
A net force is the total amount of force that is acting on the object.
Classify the solid state of the following substances as ionic crystals, covalent crystals, molecular crystals, or metallic crystals:
(a) CO2
(b) B12
(c) S8
(d) KBr
(e) Mg
(f) SiO2
(g) LiCl
(h) Cr
Explanation:
There are four type of crystals possible in solids state , given as follows -
1. Ionic crystals -
In this type of crystals ionic bond is involved for the bonding between two atoms , which connects two oppositely charged atoms , i.e. , cation and anion together .
The ionic crystal from the given options are -
(d) KBr and (g) LiCl .
2. Covalent crystals -
The bond formed in these type of crystals are from share the electrons , i.e. making a covalent bond .
Hence ,
From the given options , the covalent crystals are -
(b) B₁₂ and (f) SiO₂ .
3. Molecular crystals -
weak intermolecular forces , like the dispersion forces , holds the atoms together , generating a molecular crystal .
Hence ,
From the given options , the molecular crystals are -
(a) CO₂ and (c) S₈
4. Metallic crystal -
The type of bond , which make up a metallic crystal is , the metal cation with the delocalized electrons .
Hence ,
From the given options , the metallic crystals are -
(e) Mg and (h) Cr
You would like to induce a transversion mutation into a sequence of dna. Which type of chemical mutagen would give you the best chance of inducing the correct mutation without causing transition mutations as well?
Answer:
The type of chemical mutagen to choose depends on the intended effect. In this case, the best ones are acridines and nitrous acid.
Explanation:
Brenner et al. proposed that acridines induce mutations by causing deletions or additions of single base pairs during replication. Acridines bind to DNA by intercalation between adjacent base pairs. Acridines inactivate extracellular phage by photodynamic action but the necessary conditions for this killing
are avoided in the procedure for acridine-induced mutation of reproducing phage. The lack of reported acridine-induced mutation in organisms other than phage raises some questions as to the generality of its
mutagenesis, thus making it a good type of compounds to induce specific mutations.
In the other hand, nitrous acid deaminates the amino bases adenine, cytosine (and hydroxymethylcytosine) , and guanine in nucleic acids.
Analysis of the effect of differences of pH during nitrous acid treatment
of phage DNA showed that the rate of killing was affected similarly to
the rate of guanine deamination, and that the rates of induced r mutation was affected similarly to the rates of adenine and hydroxymethylcytosine deamination. Ascribing the induced mutations to deamination of adenine and cytosine is reasonable in terms of the hydrogen bonding of their products and the Watson-Crick base pairing schemes. Since this inorganic acid is molecule-specific, it would also be used to induce certain mutations in bacteria without causing transition mutations.
One liter of a gas is in a sealed chamber containing a moveable piston. If the piston is moved so that the volume of the gas is compressed to a volume of one-half liter, what will happen to the pressure on the gas? (Assume the temperature is constant and no gas particles are lost.)
a)The pressure will be twice the original value.
b)The pressure will be half of the original value.
c)It would be impossible to move the piston since gases are not compressible.
d)The pressure will remain the same.
Answer:
a) The pressure wiil be twice the original value
Explanation:
Pressure in inversely proportional to volume, that means; when one value decreases at the same rate that the other increases, if the temperature and amount of gas remain unchanged within a closed system. The above derived from the same definition of pressure. The pressure is defined as the crashes and frequency of the same agains surface of objects, if certain amount of gas is contained in a recipent, It will crash more times if the volume is minor. The Boyle´s law express this mathematically.
[tex]P1V1= P2V2\\\\P2=\frac{P1V1}{V2} \\\\P2=\frac{P1*1L}{0.5L} \\\\P2=2P1\\\\\\where\\\\V1= 1L\\V2= 0.5L[/tex]
At what pressure does ethane (C₂H₆) have a density of 37.2 g/L at 40.0 °C?
Answer:
At 31.88 atm pressure of ethane will have density of 37.2 g/L at 40.0 °C.
Explanation:
To calculate the pressure of gas, we use the equation given by ideal gas equation:
[tex]PV=nRT[/tex]
Number of moles (n)
can be written as: [tex]n=\frac{m}{M}[/tex]
where, m = given mass
M = molar mass
[tex]PV=\frac{m}{M}RT\\\\PM=\frac{m}{V}RT[/tex]
where,
[tex]\frac{m}{V}=d[/tex] which is known as density of the gas
The relation becomes:
[tex]PM=dRT[/tex]
Where :
P = pressure of the gas
R = universal gas constant
T = temperature of the gas
We are given with:
Density of the gas = d = 37.2 g/L
Molar mass of the ethane gas = M = 30 g/mol
Temperature of the ethane gas = T = 40.0°C= 313.15 K
Pressure of the ethane gas = P
[tex]P=\frac{dRT}{M}=\frac{37.2 g/L\times 0.0821 atm L/mol K\times 313.15 K}{30 g/mol}[/tex]
P = 31.88 atm
At 31.88 atm pressure of ethane will have density of 37.2 g/L at 40.0 °C.
The pressure of an ethane gas with a density of 37.2 g/L at 40.0 °C is equal to 31.87 atm.
Given the following data:
Density = 37.2 g/LTemperature = 40.0 °CMolar mass ([tex]C_2H_6[/tex]) = [tex](12 \times 2 + 1 \times 6) = (24+6) =30 \;g/mol[/tex]
Ideal gas constant, R = 0.0821L⋅atm/mol⋅K
Conversion:
Temperature = 40.0 °C to K = [tex]273 +40=[/tex] 313K
To find the pressure of ethane gas, we would use the ideal gas law equation;
[tex]PV = nRT[/tex]
Where;
P is the pressure. V is the volume. n is the number of moles of substance. R is the ideal gas constant. T is the temperature.[tex]Density = \frac{Mass}{Volume}[/tex]
In terms of density, the ideal gas law equation becomes:
[tex]Density = \frac{M_MP}{RT}[/tex]
Where;
[tex]M_M[/tex] is the molar mass.Making P the subject of formula, we have;
[tex]P = \frac{DRT}{M_M}[/tex]
Substituting the given parameters into the formula, we have;
[tex]P = \frac{37.2 \times 0.0821 \times 313}{30}\\\\P = \frac{955.94}{30}[/tex]
Pressure, P = 31.87 atm.
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What is the difference between stating "The electron is located at a particular point in space" and "There is a high probability that the electron is located at a particular point in space"? Choose all that apply. A. In the first statement we know where electron is. B. In the second statement, we are saying that we have no information about the position of the electron. C. In the second statement, we are saying that we know the probability of the electron being at a point, but we dont know exactly where it is. D. In the first statement, we cannot define the exact location of the electron.
The difference between stating "The electron is located at a particular point in space" and "There is a high probability that the electron is located at a particular point in space" is in the first statement, we cannot define the exact location of the electron.
What is an electron ?The elementary electric charge of the electron is a negative one, making it a subatomic particle. Due to their lack of known components or substructure, electrons, which are members of the first generation of the lepton particle family, are typically regarded to be elementary particles.
Quarks make up protons and neutrons, but not electrons. As far as we can know, quarks and electrons are basic particles that are not composed of lesser particles.
Thus, option D is correct.
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Without doing any calculations, determine which sample contains the most atoms.
a. a 1-g sample of thorium
b. a 1-g sample of boron
c. a 1-g sample of zinc
Answer:
B.
Explanation:
1g of Boron has the most number of atoms. This is simply because it has the highest number of moles.
Since 1 mole contain 6.22 × 10^23 atoms, the atom that has most moles closer to 1 will contain most atoms.
This in fact can be calculated from the fact that the number of moles equal mass divided by the atomic mass.
The mass here is equal I.e 1g and thus the dividing factor will be the atomic mass. The atom with the highest atomic mass here us thorium and thus will give the lowest number of moles. Zinc follows suit in that order with Boron at the top of the other and thus will contain the highest number of atoms.
How is carbon moved from the hydrosphere to the atmosphere?
Answer:
Explained
Explanation:
the various ways of input of CO_2 into the atmosphere.
1.Dissolved CO 2 in the ocean is released back into the atmosphere by heating ocean surface water
2.Plant and animal respiration, an exothermic reaction involving the breakdown into CO 2 and water of organic molecules.
3. Degradation of fungi and bacteria which are responsible for breaking down carbon compounds in dead animals and plants(fossils) and convert carbon into CO2 when oxygen or methane is present.
4.Combustion of organic matter (that includes deforestation and combustion of fossil fuels) oxidizing to produce CO2;
5. Cement production when calcium carbonate (limestone) is heated to produce calcium oxide(lime), cement component, and CO2 are released;
A 50.00-mL sample containing La31 was treated with sodium oxalate to precipitate La2(C2O4)3, which was washed, dissolved in acid, and titrated with 18.04 mL of 0.006 363 M KMnO4. Write the titration reaction and find [La31] in the unknown.
Answer:
2KMnO₄ + 5H₂C₂O₄ + 3H₂SO₄ → 2MnSO₄ + 10CO₂ + 8H₂O + K₂SO₄
0,02658g of La in the unknown
Explanation:
The reaction of La₂(C₂O₄)₃ with acid is:
La₂(C₂O₄)₃ + 6H⁺ → 3H₂C₂O₄ + 2La³⁺
The titration of H₂C₂O₄ with KMnO₄ is:
2KMnO₄ + 5H₂C₂O₄ + 3H₂SO₄ → 2MnSO₄ + 10CO₂ + 8H₂O + K₂SO₄
The moles of KMnO₄ that react are:
0,006363M KMnO₄×0,01804L = 1,148x10⁻⁴moles of KMnO₄
By the titration reaction, 2 moles of KMnO₄ react with 5 moles of H₂C₂O₄, that means:
1,148x10⁻⁴moles of KMnO₄×[tex]\frac{5molesH_{2}C_{2}O_{4}}{2molesKMnO_{4}}[/tex] = 2,870x10⁻⁴ moles of H₂C₂O₄.
In the reaction of La₂(C₂O₄)₃ with acid, 3 moles of H₂C₂O₄ were produced while 2 moles of La³⁺ were produced, that means:
2,870x10⁻⁴ moles H₂C₂O₄× [tex]\frac{2molesLa^{3+}}{3molesH_{2}C_{2}O_{4}}[/tex] = 1,913x10⁻⁴ moles of La³⁺, in grams -Using molar mass of lanthanum-:
1,913x10⁻⁴ moles of La³⁺×[tex]\frac{138,9g}{1mol}[/tex] = 0,02658g of La
There are 0,02658g of La in the unknown
I hope it helps!
An open-tube manometer is used to measure the pressure in flask. The atmospheric pressure is 756 torr and the Hg column is 10.5 cm higher on the open end. What is the pressure in the flask?
Answer:
P flask = 860.966 torr
Explanation:
⇒ P open tube = Patm + (δHg)(g)(h) = P flask
∴ δHg = 13.6 g/cm³
∴ g = 980 cm/s²
∴ h = 10.5 cm
⇒ (δHg)(g)(h) = (13.6 g/cm³)(980 cm/s²)(10.5 cm) = 139944 g/cm.s²
⇒ (δHg)(g)(h) = (13994.4 Kg/m.s²(Pa))×( 0.00750062 torr/Pa)
⇒ (δHg)(g)(h) = 104.966 torr
⇒ P flask = 756 torr + 104.966 torr
⇒ P flask = 860.966 torr
Using the manometer equation, the pressure in the flask is calculated as 898.8 torr. The height difference of the mercury columns, 10.5 cm, is converted to torr using the density of mercury.
- Atmospheric pressure [tex](\(P_{\text{atm}}\))[/tex] = 756 torr
- Height difference = 10.5 cm
Convert the height difference to torr using the density of mercury [tex](\(13.6 \, \text{g/cm}^3\)):\[ \text{height difference in torr} = 10.5 \, \text{cm} \times \left(\frac{13.6 \, \text{g/cm}^3}{1 \, \text{cm}}\right) = 142.8 \, \text{torr} \][/tex]
Now, apply the manometer equation:
[tex]P_{flask} - P_{atm}[/tex] = height difference in torr
P_flask - 756 torr = 142.8 torr
Solve for P_flask:
[tex]\[ P_{\text{flask}} = 756 \, \text{torr} + 142.8 \, \text{torr} = 898.8 \, \text{torr} \][/tex]
Therefore, the pressure in the flask is 898.8 torr.
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The wavelength of light associated with the n = 2 to n = 1 electron transition in the hydrogen spectrum is 1.216 × 10–7 m. By what coefficient should this wavelength be multiplied to obtain the wavelength associated with the same electron transition in the Li2+ ion?
Go through each step, and explain in detail.
Answer:
The coefficient should be 0.1111.
Explanation:
Using Rydberg's Equation:
[tex]\frac{1}{\lambda}=R_{H}\times Z^2\left(\frac{1}{n_i^2}-\frac{1}{n_f^2} \right )[/tex]
Where,
[tex]\lambda[/tex] = Wavelength of radiation
[tex]R_H[/tex] = Rydberg's Constant
[tex]n_f[/tex] = Higher energy level
[tex]n_i[/tex]= Lower energy level
Z = Atomic number
1) For n = 2 to n = 1 in hydrogen atom:
Z = 1
[tex]\frac{1}{\lambda}=R\times 1^2\left(\frac{1}{2^2}-\frac{1}{1^2} \right )[/tex]
[tex]\frac{1}{\lambda}=-R\times \frac{3}{4}[/tex]..[1]
2) For n = 2 to n = 1 in lithium ion i.e. [tex]Li^{2+}[/tex] :
Z = 3
[tex]\frac{1}{\lambda}=R\times 3^2\left(\frac{1}{2^2}-\frac{1}{1^2} \right )[/tex]
[tex]\frac{1}{\lambda '}=-9R\times \frac{3}{4}[/tex]..[2]
[2] ÷ [1]
[tex]\frac{\frac{1}{\lambda '}}{\frac{1}{\lambda }}=\frac{-9R\times \frac{3}{4}}{-R\times \frac{3}{4}}[/tex]
[tex]\frac{\lambda }{\lambda '}=9[/tex]
[tex]\lambda '=\lambda \times \frac{1}{9}[/tex]
[tex]\lambda '=\lambda \times 0.1111[/tex]
The coefficient should be 0.1111.
To find the wavelength associated with the same electron transition in the Li2+ ion, use the formula wavelength_Li2+ = (wavelength_Hydrogen) * (Z^2) / (n^2), where Z is the atomic number of the Li2+ ion and n is the principal quantum number.
Explanation:To find the wavelength associated with the same electron transition in the Li2+ ion, we need to use the formula:
wavelength_Li2+ = (wavelength_Hydrogen) * (Z^2) / (n^2)
where Z is the atomic number of the Li2+ ion (which is 3) and n is the principal quantum number (which is 2 in this case).
Plugging in the values, we have:
wavelength_Li2+ = (1.216 × 10–7 m) * (3^2) / (2^2)
Simplifying, we get the wavelength associated with the n = 2 to n = 1 electron transition in the Li2+ ion to be approximately 1.824 × 10–7 m.
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The value of ΔH for the reaction below is -72 kJ. __________ kJ of heat are released when 1.0 mol of HBr is formed in this reaction. H 2 (g) + Br 2 (g) → 2HBr (g)
The study of chemicals and bonds is called chemistry. There are different types of elements are there and these are metal and nonmetal.
The correct answer is 36 KJ of heat is released when 1.0 mole of HBr is formed.
What is Hess's law?The heat of any reaction ΔH for a specific reaction is equal to the sum of the heats of reaction for any set of reactions which in sum are equivalent to the overall reaction:[tex]H_2 (g) + Br_2 (g) ---> 2HBr (g) \ \ \ \ H = -72 KJ[/tex]
This is the energy released when 2 moles of HBr is formed from one mole each of H2 and Br2. Therefore, Heat released for the formation of 1 mol HBr would behalf on this.
ΔHreq = -36 kJ
36 KJ of heat is released when 1.0 mole of HBr is formed.
Hence, the correct answer is 36KJ.
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The energy change ΔH for the reaction of H2 with Br2 to form 2 moles of HBr is -72 kJ. Therefore, when 1 mole of HBr is formed, half of this energy, which is -36 kJ, is released.
Explanation:In your question, the chemical equation shows that 2 moles of HBr are formed from the reaction of H2 with Br2, with the release of -72 kJ of heat. This energy change, ΔH, represents the amount of heat released during the reaction, indicating it's an exothermic reaction. Given that energy change corresponds to the formation of 2 moles of HBr, the heat released when 1 mole of HBr is formed would be -72 kJ divided by 2.
This results in -36 kJ released per mole of HBr formed. Thus, when 1.0 mol of HBr is formed in this reaction, -36 kJ of heat is released.
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An example of a strong _____ agent important in biochemistry is _____. The redox potential for this molecule is _____. Please choose the correct answer from the following choices
a. oxidizing; O2;
b. negative reducing; NADH;
c. positive oxidizing; NADH;
d. positive reducing; O2;
e. negative reducing; NADH;
Answer:
Option B - reducing; NADH; negative
explanation:
Nicotinamide adenine dinucleotide, or NADH, is a compound, that's more actively used in the transportation of electron chain. It's evident that produced and make use NADH than FADH2 in the process that brings about energy creation.
NADH carries electrons from one reaction to another. Its Cofactor is in two forms in cells: NAD+ accepts electron from other molecule and hence reduced as an oxidizing agent while NADH is formed by this reaction, which can be used to donate electrons because it's a reducing agent. The main function of NAD is to transfer these reactions.
Answer the following questions: On a 10-fold dilution of a weak acid, the pH will ___________________. On a 10-fold dilution of a buffered solution, the pH will ______________. If one adds a small amount of strong base to a buffered solution, the pH will _______________. Can you make a buffer using a strong acid? Explain. How can you adjust the pH of a buffer solution? Explain.
Answer:
Increase; remain constant, remain constant; No; by adjusting the acid:base ratio of the buffer.
Explanation:
On a 10-fold dilution of a weak acid, the pH will INCREASE and that is because strong acids are not found in buffers, therefore, diluting a strong acid reduces the amount of hydrogen ions,H^+ present, consequently increasing the pH.
On a 10-fold dilution of a buffered solution, the pH will REMAIN CONSTANT because diluting a buffer does not affect the pH of the buffer.
If one adds a small amount of strong base to a buffered solution, the pH will REMAIN CONSTANT because the buffer will equalize the strong base, however, the pH may increase just a little.
One can not make a buffer solution using a strong acid because Buffers are composed of a weak acid and its conjugate base or a weak base and its conjugate acid, and weak acids or bases only dissociate partially. Strong acids dissociate completely, they overpower the reaction and move the reaction to completion.
pH of a buffer solution can be adjusted using by adjusting the acid:base ratio of the buffer.
Final answer:
Diluting a weak acid increases its pH, while a buffered solution maintains a consistent pH upon dilution or the addition of a small amount of strong base. Buffers cannot be made with strong acids, and adjusting a buffer's pH involves altering the weak acid to conjugate base ratio.
Explanation:
Changes in pH with Dilution and Additions:
On a 10-fold dilution of a weak acid, the pH will increase, because the concentration of hydrogen ions decreases, making the solution less acidic.On a 10-fold dilution of a buffered solution, the pH will remain relatively constant. This stability is due to the presence of both a weak acid and its conjugate base which can absorb added acids or bases without significantly changing the pH.If one adds a small amount of strong base to a buffered solution, the pH will increase slightly. However, due to the buffering action, this change is much less than it would be in an unbuffered solution.One cannot make a buffer using a strong acid because strong acids fully dissociate in water, and a buffer relies on the equilibrium between a weak acid and its conjugate base to maintain pH. To adjust the pH of a buffer solution, one can vary the ratio of the weak acid to its conjugate base. The pH of a buffer is ideally maintained within ±1 unit of the pKa of the weak acid.
How many grams of silver chloride can be prepared by the reaction of 100.0 mL of 0.20 M silver nitrate with 100.0 mL of 0.15 M calcium chloride? Calculate the concentrations of each ion remaining in solution after precipitation is complete.
Answer:
Mass of AgCl = 2.87 g
[Ca²⁺] = 0.075 M
[Cl⁻] = 0.05 M
[NO₃⁻] = 0.10 M
Explanation:
The reaction between silver nitrate (AgNO₃) and calcium chloride (CaCl₂) is:
2AgNO₃(aq) + CaCl₂(aq) → 2AgCl(s) + Ca(NO₃)₂(aq)
The number of moles of the reactants are:
AgNO₃ = Volume (L)*concentration (M) = 0.1*0.2 = 0.02 mol
CaCl₂ = 0.1*0.15 = 0.015 mol
First, let's find which reactant is limiting. Testing for AgNO₃, the stoichiometry is:
2 moles of AgNO₃ ------------------------- 1 mol of CaCl₂
0.02 mol ------------------------- x
By a simple direct three rule:
2x = 0.02
x = 0.01 mol of CaCl₂, which is higher than was used, so CaCl₂ is in excess and AgNO₃ is the limiting reactant.
The stoichiometry between AgNO₃ and AgCl is:
2 moles of AgNO₃ ---------------- 2 moles of AgCl
0.02 mol ---------------- x
By a simple direct three rule
x = 0.02 mol of AgCl
The molar mass of AgCl is 143.32 g/mol, so the mass formed is:
m = 143.32*0.02 = 2.87 g
All the silver nitrate had reacted, and by the stoichiometry, only 0.01 mol of CaCl₂ reacted, so the number of moles remaining is:
nCaCl₂ = 0.015 - 0.01 = 0.005 mol
And the number of moles of Ca(NO₃)₂ formed is the same as CaCl₂ that reacted: 0.01 mol.
Both substances are in aqueous form, so, they produce ions:
CaCl₂ → Ca²⁺ + 2Cl⁻
By the stoichiometry: nCa²⁺ = 0.005 mol; nCl⁻ = 0.01 mol
Ca(NO₃)₂ → Ca²⁺ + 2NO₃⁻
By the stoichiometry: nCa²⁺ = 0.01 mol; nNO₃⁻ = 0.02 mol
The total volume is 0.2 L, so the ions concentrantions are:
[Ca²⁺] = (0.005 + 0.01)/0.2 = 0.075 M
[Cl⁻] = 0.01/0.2 = 0.05 M
[NO₃⁻] = 0.02/0.2 = 0.10 M
The concentrations of each ion remaining in solution after precipitation is complete is Mass of AgCl = 2.87 g, [Ca²⁺] = 0.075 M, [Cl⁻] = 0.05 m, [NO₃⁻] = 0.10 M.
What is silver chloride?Silver chloride is an ionic compound in which the silver is cation and the chloride is anion.
The reaction is
[tex]2AgNO_3(aq) + CaCl_2(aq) = 2AgCl(s) + Ca(NO_3)_2(aq)[/tex]
The number of moles of the reactants are:
[tex]AgNO_3 = Volume (L) \times concentration (M) \\\\= 0.1 \times 0.2 = 0.02 mol[/tex]
[tex]CaCl_2 = 0.1 \times 0.15 = 0.015 mol[/tex]
Now, finding the limiting reactant.
Testing for AgNO₃,
The stoichiometry is:
2 moles of AgNO₃ = 1 mol of CaCl₂
0.02 mol = x
By direct three rule:
2x = 0.02
[tex]AgNO_3[/tex] is the limiting reactant.
The stoichiometry between [tex]AgNO_3[/tex] and AgCl is:
2 moles of [tex]AgNO_3[/tex] = 2 moles of AgCl
0.02 mol = x
By a simple direct three rule
x = 0.02 mol of AgCl
The mass formed is
If the molar mass of AgCl is 143.32 g/mol
[tex]m = 143.32\times0.02 = 2.87 g[/tex]
Remaining number of moles are
nCaCl₂ = 0.015 - 0.01 = 0.005 mol
The substances will produce ions, because they are aqueous form.
[tex]CaCl_2 = Ca^2^++ 2Cl^-[/tex]
By the stoichiometry
nCa²⁺ = 0.005 mol
nCl⁻ = 0.01 mol
[tex]Ca(NO_3)_2 = Ca^2^+ + 2NO_3^-[/tex]⁻
By the rule of stoichiometry
nCa²⁺ = 0.01 mol
nNO₃⁻ = 0.02 mol
The volume is 0.2 L,
The concentration of ions are
[Ca²⁺] =[tex]\dfrac{(0.005 + 0.01)}{0.2} = 0.075 M[/tex]
[Cl⁻] = [tex]\dfrac{0.01}{0.2} = 0.05 M[/tex]
[NO₃⁻] = [tex]\dfrac{0.02}{0.2} = 0.10\; M[/tex]
Thus, the concentrations of each ion remaining in solution after precipitation is complete is Mass of AgCl = 2.87 g, [Ca²⁺] = 0.075 M, [Cl⁻] = 0.05 m, [NO₃⁻] = 0.10 M.
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Which of the following observations indicates that an atom has neutrons?
A. Some uncharged particles are scattered by a beryllium atom when it hits a gold foil.
B. Some uncharged particles bounce back from a gold foil when it is bombarded with alpha particles.
C. A radiation with neutral particles is emitted when alpha particles strike beryllium atoms.
D. A radiation which attracts electrons is produced when a beryllium atom is bombarded with alpha particles.
C
When the alpha particle hits the beryllium atoms at high speeds, it splits the atomic nuclei hence causing the nuclei particles flying. When exposed to an electric field, the path of the proton is curved towards the negative pole while neutrons are unaffected.
Explanation:
Neutrons are found in the dense part of atoms (the nucleus) along with protons. Unlike protons, however, that are positively charged, neutrons are uncharged particles. Neutrons are important in the stability of the atomic nuclei because they ensure that the positively charged particles (protons), which are cramped together in a tight space, do not repel each other because like-charges repel.
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What is the specific heat capacity of a metal if it requires 177.5 J to change the temperatures of 15.0g of the metal from 25.00 degree celcius to 34 degree celcius
Answer:
The specific heat capacity of a metal is 1.31 J/g°C = C
Explanation:
A classical excersise of calorimetry to apply this formula:
Q = m . C . ΔT
177.5 J = 15 g . C (34°C - 25°C)
177.5 J = 15g . 9°C . C
177.5 J /15g . 9°C = C
1.31 J/g°C = C
Final answer:
To find the specific heat capacity of the metal, the heat energy absorbed is divided by the product of mass and temperature change, which yields a specific heat capacity of 1.315 J/g\u00b0C.
Explanation:
To calculate the specific heat capacity of a metal with the given data, we can use the formula:
q = m \\cdot c \\cdot \\Delta T,
where q is the heat energy absorbed (in joules), m is the mass of the substance (in grams), c is the specific heat capacity (in J/g\u00b0C), and \\Delta T is the change in temperature (in degrees Celsius).
Rearranging the formula to solve for c gives:
c = q / (m \\cdot \\Delta T)
Substituting the given values:
q = 177.5 J,
m = 15.0 g,
\\Delta T = 34\u00b0C - 25\u00b0C = 9\u00b0C.
Therefore:
c = 177.5 J / (15.0 g \\cdot 9\u00b0C)
c = 177.5 J / 135 g\u00b0C
c = 1.315 J/g\u00b0C
The specific heat capacity of the metal is 1.315 J/g\u00b0C.
Sulfur dioxide has a vapor pressure of 462.7 mm Hg at –21.0 °C and a vapor pressure of 140.5 mm Hg at –44.0 °C. What is the enthalpy of vaporization of sulfur dioxide? (R = 8.314 J/K⋅mol)
Final Answer:
The enthalpy of vaporization [tex](\( \Delta H_{\text{vap}} \))[/tex]of sulfur dioxide is approximately[tex]\( 28.5 \, \text{kJ/mol} \)[/tex].
Explanation:
To find the enthalpy of vaporization [tex](\( \Delta H_{\text{vap}} \))[/tex], we use the Clausius-Clapeyron equation:
[tex]\[ \ln\left(\frac{P_2}{P_1}\right) = -\frac{\Delta H_{\text{vap}}}{R}\left(\frac{1}{T_2} - \frac{1}{T_1}\right) \][/tex]
Given vapor pressures:
[tex]\( P_1 = 462.7 \, \text{mm Hg} \) at \( T_1 = -21.0 \, \text{°C} \),[/tex]
[tex]\( P_2 = 140.5 \, \text{mm Hg} \) at \( T_2 = -44.0 \, \text{°C} \).[/tex]
Convert temperatures to Kelvin:
[tex]\[ T_1 = -21.0 \, \text{°C} + 273.15 = 252.15 \, \text{K} \][/tex]
[tex]\[ T_2 = -44.0 \, \text{°C} + 273.15 = 229.15 \, \text{K} \][/tex]
Now, substitute values into the equation:
[tex]\[ \ln\left(\frac{140.5}{462.7}\right) = -\frac{\Delta H_{\text{vap}}}{8.314}\left(\frac{1}{229.15} - \frac{1}{252.15}\right) \][/tex]
Solving for [tex]\( \Delta H_{\text{vap}} \):[/tex]
[tex]\[ \Delta H_{\text{vap}} = -8.314 \times \ln\left(\frac{140.5}{462.7}\right) \times \frac{1}{229.15 - 252.15} \][/tex]
After calculation, [tex]\( \Delta H_{\text{vap}} \)[/tex]is approximately[tex]\( 28.5 \, \text{kJ/mol} \).[/tex]
In conclusion, the enthalpy of vaporization for sulfur dioxide is determined through the Clausius-Clapeyron equation, with precise calculations yielding an enthalpy value of [tex]\( 28.5 \, \text{kJ/mol} \)[/tex].
A 1.00-L gas sample at 100.°C and 500. torr contains 52.0% helium and 48.0% xenon by mass. What are the partial pressures of the individual gases?
Answer:
Partial pressure of He=486 torr, partial pressure of Xe= 14 torr
Explanation:
Using the equation, PV=nRT----------------------------------------(1)
Making n the subject of the formula;
n= PV/RT---------------------(2)
Where n= number of moles, v= volume, T= temperature, P= volume.
n= (500 torr/760 torr × 1 atm)× 1L ÷ 373K ×0.082 L atmK^-1. Mol^-1
n= 0.6579 atm.L/ 30.6233
n= 0.0215 mol.
Let the total mass of the gas= 2b(in g).
Mass of helium gas = b (in g) = mass of Xenon gas
Mole of helium gas= b(in g) / 4 gmol^-1
=b/4 mol
Mole of Xenon= b g/131.3 gmol^-1
= b/131.3 mol.
Solving for b, we have;
b/4+b/131.3 = 0.0215 mole
(131.3+4)b/525.2= 0.0215
Multiply both sides by 1/135.3.
b= 11.2918/135.3
b= 0.0835 g
Mole of He gas= 0.0835/4= 0.0209
Mole of Xe gas= 0.0215- 0.0209
= 0.0006 mol
Mole fraction of He = 0.0209/0.0215
= 0.972
Mole fraction of Xe= 0.0006/0.0215
= 0.028
Partial pressure of He gas= 0.972× 500 torr= 486 torr
Partial pressure of Xe gas= 0.028 ×500 torr = 14 torr
Final answer:
Dalton's Law is used to find the partial pressures of He (388.7 torr) and Xe (111.3 torr) in a 1.00 L, 500 torr mixture by calculating their mole fractions based on mass percentages and multiplying by the total pressure.
Explanation:
To determine the partial pressures of helium and xenon in a 1.00-L gas sample at 100.°C and 500. torr, we can use Dalton's Law of Partial Pressures. First, we calculate the mass of each gas based on the given percentage by mass. Then, we convert the mass of each gas to moles using their respective molar masses. Finally, using Dalton's Law, the partial pressure of each gas is calculated as the mole fraction of that gas multiplied by the total pressure.
First, let's convert the total mass percentage to actual mass assuming we have 100 grams of the mixture:
Mass of helium (He) = 52.0% of 100 g = 52.0 g
Mass of xenon (Xe) = 48.0% of 100 g = 48.0 g
Next, we'll convert mass to moles using the molar mass of helium (4.00 g/mol) and xenon (131.29 g/mol):
Moles of He = 52.0 g / 4.00 g/mol = 13.0 moles
Moles of Xe = 48.0 g / 131.29 g/mol = 0.365 moles
The total moles of gas is the sum of the moles of He and Xe:
Total moles of gas = Moles of He + Moles of Xe
Total moles of gas = 13.0 moles + 0.365 moles = 13.365 moles
Next, we calculate the mole fraction for each gas:
Mole fraction of He = Moles of He / Total moles of gas = 13.0 / 13.365
Mole fraction of Xe = Moles of Xe / Total moles of gas = 0.365 / 13.365
Lastly, we determine each gas's partial pressure:
Partial pressure of He = Mole fraction of He × Total pressure
Partial pressure of Xe = Mole fraction of Xe × Total pressure
Substituting the values we get:
Partial pressure of He = (13.0 / 13.365) × 500 torr
Partial pressure of Xe = (0.365 / 13.365) × 500 torr
Partial pressures calculated are for He and Xe respectively.
The valve between a 2.00-L bulb, in which the gas pressure is 1.80 atm, and a 3.00-L bulb, in which the gas pressure is 3.40 atm, is opened. What is the final pressure in the two bulbs, the temperature remaining constant?
Answer:
2.76 atm
Explanation:
Boyle's law states that, for an isothermic process (temperature remaining the same), the product of the pressure and volume is constant.
Dalton's law states that in a gas mixture, the total pressure is the sum of the partial pressure of the components.
So:
P1*V1 + P2*V2 = P*V
Where P1 is the pressure in the bulb 1, V1 is the volume in the bulb 1, P2 is the pressure in the bulb 2, V2 is the volume in the bulb 2, P is the pressure at the mixture after the valve was opened, and V is the final volume (5.00 L).
1.80*2.00 + 3.40*3.00 = P*5.00
5P = 13.80
P = 2.76 atm
We have that for the Question "The valve between a 2.00-L bulb, in which the gas pressure is 1.80 atm, and a 3.00-L bulb, in which the gas pressure is 3.40 atm, is opened. What is the final pressure in the two bulbs, the temperature remaining constant?" it can be said that the final pressure in the two bulbs, the temperature remaining constant
P_f=2.44atm
From the question we are told
The valve between a 2.00-L bulb, in which the gas pressure is 1.80 atm, and a 3.00-L bulb, in which the gas pressure is 3.40 atm, is opened. What is the final pressure in the two bulbs, the temperature remaining constant?
Generally the equation for the ideal gas is mathematically given as
[tex]Pv=nRT[/tex]
Where
[tex]n_1=\frac{PV}{RT}\\\\n_1=\frac{1.80*3}{RT}\\\\n_1=\frac{5.4}{RT}\\\\[/tex]
[tex]n_2=\frac{PV}{RT}\\\\n_2=\frac{3.4*2}{RT}\\\\n_2=\frac{5.4}{RT}+\frac{6.8}{RT}\\\\[/tex]
Where
[tex]the total moles =\frac{5.4}{RT}+\frac{6.8}{RT}\\\\the total moles =\frac{12.2}{RT}[/tex]
Therefore
[tex]P_f*5=\frac{12.2}{RT}*RT[/tex]
P_f=2.44atm
Hence, the final pressure in the two bulbs, the temperature remaining constant
P_f=2.44atm
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What is the equation for the energy levels of the hydrogen atom
Answer: E = (13.6 eV) [1/nf² - 1/ni²]
En = (-13.6 eV)/n²
where n=1,2,3...
Explanation:
According to Bohr's theory each spcified energy value( E1,E2,E3...) is called energy level of the atom and the only allowable values are given by the equation
En = (-13.6 eV)/n²
The energy change (ΔE) that accompaies the leap of an electron from one energy level to another is given by equation
E = (13.6 eV) [1/nf² - 1/ni²]
The equation for the energy levels of the hydrogen atom is given by the Bohr formula: En = -13.6 eV / n^2. The energy levels are inversely proportional to the square of the principal quantum number.
Explanation:The question concerns the equation for the energy levels of the hydrogen atom. According to Bohr's model, the energy levels of a hydrogen atom, which consists of a single electron orbiting a single proton, are given by the formula:
En = -13.6 eV / n2
Here, En represents the energy of an electron at a particular level n, which is known as the principal quantum number. This number can be any positive integer (n = 1, 2, 3, ...), and the energy level becomes less negative as n increases. The ground state energy of the hydrogen atom, when n = 1, is
-2.18 x 10-18 joules
Transitions between these energy levels result in the emission or absorption of light at specific wavelengths, giving rise to the hydrogen spectral series. Notably, the Lyman series corresponds to transitions ending at n=1, and the Balmer series ends at n=2.
Calculate the ph of a buffer that is 0.145 m hc2h3o2 and 0.202 m kc2h3o2. The ka for hc2h3o2 is 1.8 × 10-5.
Answer:
pH = 4.8
Explanation:
A buffer is formed by a weak acid (0.145 M HC₂H₃O₂) and its conjugate base (0.202 M C₂H₃O₂⁻ coming from 0.202 M KC₂H₃O₂). The pH of a buffer system can be calculated using Henderson-Hasselbalch's equation.
[tex]pH = pKa + log\frac{[base]}{[acid]} \\pH = -log(1.8 \times 10^{-5} )+log(\frac{0.202M}{0.145M} )\\pH=4.8[/tex]
An experiment reacts 20.4 g of zinc metal with a solution containing an excess of iron (III) sulfate. After the reaction, 10.8 grams of iron metal are recovered. What is the percent yield of the experiment?
Answer:
The answer to your question is 92.7%
Explanation:
Balanced Chemical reaction
3 Zn + Fe₂(SO₄)₃ ⇒ 2Fe + 3ZnSO₄
Molecular weight
Zinc = 65.4 x 3 = 196.2g
Iron (III) = 56 x 2 = 112 g
Proportions
196.2 g of Zinc ------------------ 112 g of Iron
20.4 g of Zinc ----------------- x
x = (20.4 x 112) / 196.2
x = 2284.8/196.2
x = 11.65 g of Iron
% yield = [tex]\frac{10.8}{11.65} x 100[/tex]
% yield = 0.927 x 100
% yield = 92.7
Which pair of molecules has the strongest dipole-dipole interactions?
CH4 and CH4 NH3 and CH4 CO2 and CH4 NH3 and NH3 CO2 and CO2
Answer: NH3 and NH3
Explanation:
If hydrogen is bonded to a highly electronegative element, a strong dipole-dipole attraction is set up with strength ten times greater than normal dipole-dipole attractions, and it is crystal clear that electronegativity increase from left to right across the period and it decreases down the group. Nitrogen being electronegative more than Oxygen will exhibit a greater dipole-dipole attraction. As such, NH3 and NH3 is the right answer.
The pair of molecules with the strongest dipole-dipole interactions among the given options is NH3 and NH3 due to the molecule's polar nature and resultant net dipole.
Explanation:Among the options listed, the pair of molecules with the strongest dipole-dipole interactions is NH3 and NH3. Dipole-dipole interactions are attractive forces between the positive end of one polar molecule and the negative end of another polar molecule. They occur when the molecule is polar, meaning there is an unequal distribution of electrons and hence a net dipole. NH3, or ammonia, is a polar molecule because it has a pyramidal shape with a net dipole. This results in strong dipole-dipole interactions between NH3 molecules, stronger than CH4 (methane) with CH4, CO2 (carbon dioxide) with CO2, or NH3 with CH4 as these molecules are nonpolar and thus exhibit weaker London dispersion forces and not dipole-dipole interactions.
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A bomb calorimetric experiment was run to determine the enthalpy of combustion of methanol. The reaction is CH3OH(l)+3/2O2(g)→CO2(g)+2H2O(l) The bomb calorimeter has a heat capacity of 250.0 J/K. Burning 0.028 g of methanol resulted in a rise in temperature from 21.50 ∘C to 23.41 ∘C. Calculate the change in internal energy for the combustion of methanol in kJ/mol.
Answer:
The change in internal energy during the combustion reaction is- 545.71 kJ/mol.
Explanation:
First we have to calculate the heat gained by the calorimeter.
[tex]q=c\times (T_{final}-T_{initial})[/tex]
where,
q = heat gained = ?
c = specific heat = [tex]250.0 J/^oC[/tex]
[tex]T_{i}[/tex] = Initial temperature = [tex]21.50^oC=294.65 K[/tex]
[tex]T_{f}[/tex] = Final temperature = [tex]23.41^oC=296.56 K[/tex]
Now put all the given values in the above formula, we get:
[tex]q=250.0 J/K\times (296.56 -294.65 )K[/tex]
[tex]q=477.5 J [/tex]
Now we have to calculate the enthalpy change during the reaction.
[tex]\Delta H=-\frac{q}{n}[/tex]
where,
[tex]\Delta H[/tex] = enthalpy change = ?
q = heat gained = -477.5 J
n = number of moles methanol = [tex]\frac{\text{Mass of methanol}}{\text{Molar mass of methanol}}=\frac{0.028 g}{32 g/mol}=0.000875 mol[/tex]
[tex]\Delta H=-\frac{477.5 }{0.000875 mol}=-545,714.28 J/mol=-545.71 kJ/mol[/tex]
Therefore, the change in internal energy during the combustion reaction is- 545.71 kJ/mol.
covalent bonds are formed from the sharing of valence electrons
true or false give a brief simple explanation
Answer:true
Explanation:
In covalent bond, lone pair of electrons are shared by the reacting species inorder to achieve a stable duplet or octet condition.as a result, molecules and not ions are formed
Solution: The ΔHvap of a certain compound is 48.17 kJ mol-1 and its ΔSvap is 52.91 J mol-1•K-1. What is the boiling point of this compound?
Answer: 910.44K
Explanation:
From the question, the parameters given are; ∆H(vaporization)= 48.17 kJ/mol and ΔS(vaporization)= 52.91 J mol-1•K.
Using the formula;
dG = dH - TdS -------------------------(1).
Here, dG=0, dG= change in free energy.
dH(vaporization) = 48,170 J/mol
dS(vaporization) = 52.91 J/mol.K
Boiling point of the substance, T=???
Therefore, we solve for T(temperature, that is the boiling point-boiling temperature) of the compound in Kelvin.
Slotting in the parameters given into equation (1). We have;
0= 48,170 J/mol - T× 52.91 J/mol.K
=> 48,170= 52.91T
T= 910.44 K
The boiling point of a compound can be calculated using the formula T = ΔHvap / ΔSvap. For this compound, with ΔHvap of 48.17 kJ mol-1 and ΔSvap of 52.91 J mol-1•K-1, the estimated boiling point is around 908 K.
Boiling point is the temperature at which a substance changes from a liquid to a gas. To calculate it, you can use the formula ΔGvap = ΔHvap - TΔSvap where ΔGvap is Gibbs free energy of vaporization, ΔHvap is enthalpy of vaporization, T is temperature in Kelvin, and ΔSvap is entropy of vaporization.
To find the boiling point of the compound, rearrange the formula as T = ΔHvap / ΔSvap. Substituting the given values, T = 48.17 kJ mol-1 / (52.91 J mol-1*K-1 / 1000) = approximately 908 K.
The energy change, ∆H, associated with the following reaction is +81 kJ.
NBr3(g) + 3 H2O(g) → 3 HOBr(g) + NH3(g)
What is the expected energy change for the reverse reaction of nine moles of HOBr and two moles of NH3?
1.) -81 kJ
2.) +162 kJ
3.) +243 kJ
4.) -365 kJ
5.) -243 kJ
6.) +365 kJ
7.) +81 kJ
8.) -162 kJ
Answer:
Expected energy change is -162kJ
Explanation:
For the reaction:
NBr₃(g) + 3H₂O(g) → 3HOBr(g) + NH₃(g) ΔH = +81kJ
For the reverse reaction, ΔH changes sign, thus:
3HOBr(g) + NH₃(g) → NBr₃(g) + 3H₂O(g) ΔH = -81kJ
If 2 moles of NH₃ react, the ΔH must be multiplied twice:
6HOBr(g) + 2NH₃(g) → 2NBr₃(g) + 6H₂O(g) ΔH = -162kJ
As you have 9 moles of HOBr, the limitng reactant is NH₃. Thus, expected energy change is -162kJ
I hope it helps!
Purification of chromium can be achieved by electrorefining chromium from an impure chromium anode onto a pure chromium cathode in an electrolytic cell. How many hours will it take to plate 11.0 kg of chromium onto the cathode if the current passed through the cell is held constant at 41.5 A? Assume the chromium in the electrolytic solution is present as Cr₃. ______ h.
Explanation:
It is given that mass is 11 kg. Convert mass into grams as follows.
[tex]11 kg \times \frac{1000 g}{1 kg}[/tex]
= 11000 g (as 1 kg = 1000 g)
Now, calculate the number of moles as follows.
No. of moles = [tex]\frac{\text{Mass of Cr}}{\text{Molar mass of Cr}}[/tex]
= [tex]\frac{11000 g}{52 g/mol}[/tex]
= 211.54 mol
For [tex]Cr^{3+}[/tex], 3 moles of electrons are required
Hence, [tex]3 \times 211.54 mol[/tex]
= 634.62 mol
As 1 mol of electrons contain 96500 C of charge. Therefore, charge carried by 634.62 mol of electrons will be calculated as follows.
Q = [tex]634.62 mol \times 96500 C/mol [/tex]
= [tex]61.24 \times 10^{6} C[/tex] of charge
We know that relation between charge, current and time is as follows.
Q = [tex]I \times t[/tex]
Current is given as 41.5 A and charge is calculated as [tex]61.24 \times 10^{6} C[/tex]. Therefore, calculate the time as follows.
Q = [tex]I \times t[/tex]
[tex]61.24 \times 10^{6} C = 41.5 A \times t[/tex]
t = [tex]1.47 \times 10^{6} sec[/tex]
As there are 3600 seconds in one 1 hour. Therefore, converting [tex]1.47 \times 10^{6} sec[/tex] into hours as follows.
[tex]\frac{1.47 \times 10^{6} sec}{3600 sec/hr}[/tex]
= 4.09 hr
Thus, we can conclude that it takes 4.09 hours to plate 11.0 kg of chromium onto the cathode if the current passed through the cell is held constant at 41.5 A.
The process of electrorefining chromium involves oxidation of Chromium III ions at anode and reduction at the cathode. The total charge required for this process can be calculated using Faraday's law, and the time required to pass this charge can be calculated using the formula Q/I. Therefore, it will take approximately 408 hours to plate 11kg of chromium onto the cathode with 41.5 A current.
Explanation:The process of electrorefining chromium involves two half-reactions at anode and cathode in which chromium is oxidized at the anode and is then reduced at the cathode. Specifically, Chromium III ion (Cr³+) is oxidized at the anode with the reaction Cr³+ (aq) + 3e-, and is then reduced at the cathode. The stoichiometry of this process requires three moles of electrons for each mole of chromium(0) produced. Given this stoichiometry and the current passed through the cell, we can calculate the time required to plate 11kg of chromium.
First, since the molar mass of chromium is approximately 52 g/mol, 11kg is equal to about 211.5 mol. This number of moles of chromium requires [tex]211.5 * 3 = 634.5[/tex] mol of electrons. One mol of electrons carries a charge of approximately 96485 Coulombs (C), so the total charge is approximately [tex]6.115 * 10^7 C.[/tex]
If this charge is being passed at 41.5 C/s, the time required to pass the total amount of charge can be calculated by the formula Q/I, where Q represents the total charge and I represents the current. Therefore, the time required to plate 11kg of chromium onto the cathode with 41.5 A current is approximately [tex]1.47 * 10^6[/tex] seconds which is approximately 408 hours.
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