Answer:
A solution that is 0.100 M (i.e. 33,12 g of lead (II) nitrate in 1.00 L of water) yields the desired total dissolved ions concentration.
Explanation:
The molecular formula of lead (II) nitrate is Pb(NO[tex]Pb(NO_{3} )_{2}[/tex] and its molecular mass is 331,2 g/mol.
In disolution, the equilibrium will look like this:
Pb(NO[tex]Pb(NO_{3} )_{2}[/tex] -> [tex]Pb^{2+} + 2(NO)_{3} ^{-1}[/tex]
The equation above means that, one mol of lead (II) nitrate dissolved in 1L will yield one mol of Pb ions and 2 moles of NO3 ions, i.e. 3 moles total.
If we dissolve 0.100 moles of lead (II) nitrate in 1.00 L of water, the stoichiometry of the disolution states that in turn, it will yield 0.100 of Pb ions and 0.200 moles of NO3 ions, i.e. 0.300 M in total dissolved ions.
331,2 g/mol * 0.100 mol/L * 1 L = 33,12 grams of the compound are required.
Fireworks that contain metallic salts such as sodium, strontium, and barium can generate bright colors. A technician investigates what colors are produced by the metallic salts by performing flame tests. During a flame test, a metallic salt is heated in the flame of a gas burner. Each metallic salt emits a characteristic colored light in the flame. 3. State how bright-line spectra viewed through a spectroscope can be used to identify the metal ions in the salts used in the flame tests. 4. Explain, in terms of electrons, how a strontium salt emits colored light. 5. Explain why the electron configuration of 2-7-1-1 represents a sodium atom in an excited state.
Answer:
See explanation below
Explanation:
3. Each atom has unique electron energy level when compared to other, when electron relaxes from an excited energy level, it emits energy in the form of electromagnetic waves with energy equals to the difference between energy of ground and excited state. As electromagnetic wave wavelength obeys planck relation
[tex]c = \lambda f[/tex]
And the energy of each photon in electromangetic wave of specific frequency is
[tex]E=hf[/tex]
Where h is planck's constant
We can see that the wavelength, which determines color and position of bright line in spectroscope corresponds directly to the energy of electromagnetic wave, and thus, the characteristic energy of atom.
4. From the answer above, you now know that electronic transition can emit electron with specific wavelength. In strontium, emission of colored light occurs by the relaxation of electrons in excited state such that the difference between excited energy level and ground level falls in the energy of visible light spectral range.
5. In Na, ground state configuration is 2-8-1. 2-7-1-1 indicates that one of electron in ground state got excited by external energy to excited state, and thus, indicates that Na atom is in excited state
Final answer:
Bright-line spectra viewed through a spectroscope can be used to identify the metal ions in salts used in flame tests.
Explanation:
Bright-line spectra viewed through a spectroscope can be used to identify the metal ions in the salts used in flame tests. Each metal ion has a unique set of energy levels, and when these ions are heated in a flame, their electrons get excited and jump to higher energy levels. As the electrons return to their ground states, they release energy in the form of light. This emitted light can be observed through a spectroscope, which separates the different wavelengths of light, creating a bright-line spectrum. By comparing the bright-line spectrum of an unknown salt to the known spectra of different metal ions, the metal ions present in the unknown salt can be identified.
Aerosol cans have a label that warns the user not to use them above a certain temperature and not to dispose of them by incineration. Even an empty can contains residual gaseous propellant. For example, the residual pressure in a can is 1.11 atm when it is sitting on a shelf at 23 ∘C. If the can is placed on top of the furnace where the temperature reaches the boiling point of water, what is the pressure inside the can?
Answer:
1.40 atm
Explanation:
To answer this question we can use Gay-Lussac's law, which states:
P₁T₂=P₂T₁When volume and number of moles remain constant.
P₁ = 1.11 atmT₁ = 23°C ⇒ 23+273.16 = 296.16 KT₂ = Boiling point of water = 100 °C ⇒ 100+273.16 = 373.16 KP₂ = ?We put the known data in the equation and solve for P₂:
1.11 atm * 373.16 K = P₂ * 296.16 KP₂ = 1.40 atmUsing the ideal gas law, the pressure inside an aerosol can increases proportionately with temperature. If the can's temperature is raised to the boiling point of water (100°C or 373 K), the pressure increases from 1.11 atm to 1.40 atm.
Explanation:The pressure inside an aerosol can, like this one which has a residual propellant, can be explained by the ideal gas law, which states that the pressure of a gas is directly proportional to its temperature when the volume and amount of gas are held constant. If the can is heated to the boiling point of water (100°C or 373 K), we can expect the pressure to increase proportionately.
To find out the new pressure, we need to convert the initial temperature to Kelvin (23°C = 296 K), and then use the formula P1/T1 = P2/T2 where P1 is the initial pressure, T1 is the initial temperature, P2 is the pressure at elevated temperatures, and T2 is the temperature at the boiling point of water.
So, P2 = P1×T2/T1 = 1.11 atm × 373 K / 296 K = 1.40 atm. Therefore, the pressure inside the can at the boiling point of water is 1.40 atm.
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Which of the following is true about halogens? Group of answer choices
they have seven valence electrons
they have two valence electrons
they have one valence electron
they have eight valence electrons
Answer:they have one valence electron
Explanation:halogens are in group seven of the periodi table and they have seven electrons in their outermost shell thus need one electron to complete their octet condition. Thus goes into combination to accept one electrons from another element and that is their combining power which is their valency.
The halogens have seven valence electrons.
• In the periodic table, the elements present in group 7A are known as halogens.
• These are fluorine, chlorine, bromine, iodine, and astatine.
• The halogen term means salt former.
• The major characteristic of halogens is that they have seven valence electrons in their higher energy orbitals.
• They are one electron behind in forming a full octet, so these elements would seem to produce anions exhibiting -1 charges and are known as halides.
Thus, halogens having seven valence electrons is the right statement.
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The stopcock connecting a 4.87 L bulb containing hydrogen gas at a pressure of 4.38 atm, and a 4.87 L bulb containing argon gas at a pressure of 2.90 atm, is opened and the gases are allowed to mix. Assuming that the temperature remains constant, the final pressure in the system is _____atm
Answer:
P = 3,63 atm
Explanation:
Using PV=nRT and knowing the temperature in the problem remains constant it is possible to rewrite this formula, thus:
PV = kn, where k is RT (Constant), P is pressure, V is volume and n are moles.
The first bulb contains:
4,87L×4,38atm = 21,3k moles
And the second bulb:
4,87L×2,90atm = 14,1k moles
When gases are mixed, the total moles are:
21,3k moles + 14,1k moles = 35,4k moles
As total volume is 4,87L + 4,87L = 9,74L
Replacing:
P = kn/V
P = 35,4k moles / 9,74L
P = 3,63 atm
I hope it helps!
HCl gas is introduced at one end of the tube, and simultaneously NH3 gas is introduced at the other end. When the two gases diffuse through the cotton plugs down the tube and meet, a white ring appears due to the formation of NH4Cl(s). Why is this?
Answer:
When the two gases are mixed, the ammonium chloride precipitates in the tube walls.
Explanation:
This is the reaction:
HCl (g) + NH₃(g) → NH₄Cl (s) ↓
As the product formed is solid at room temperature, a suspension is first formed in the internal air of the tube that appears as a cloud. Afterwards it finally precipitates into the walls forming a white layer
The following change occurs in acidic solution: S^2+ + Cr_2O_7^2+ S + Cr^3+ Complete and balance the foregoing equation. In the balanced equation, for every mole of Cr_2O_7^2 that reacts, moles of H+ are consumed. A. 5 B. 7 C. 8 D. 10 E. 14
Answer : The correct option is, (E) 14
Explanation :
Redox reaction or Oxidation-reduction reaction : It is defined as the reaction in which the oxidation and reduction reaction takes place simultaneously.
Oxidation reaction : It is defined as the reaction in which a substance looses its electrons. In this, oxidation state of an element increases. Or we can say that in oxidation, the loss of electrons takes place.
Reduction reaction : It is defined as the reaction in which a substance gains electrons. In this, oxidation state of an element decreases. Or we can say that in reduction, the gain of electrons takes place.
Rules for the balanced chemical equation in acidic solution are :
First we have to write into the two half-reactions.Now balance the main atoms in the reaction.Now balance the hydrogen and oxygen atoms on both the sides of the reaction.If the oxygen atoms are not balanced on both the sides then adding water molecules at that side where the less number of oxygen are present.If the hydrogen atoms are not balanced on both the sides then adding hydrogen ion [tex](H^+)[/tex] at that side where the less number of hydrogen are present.Now balance the charge.The given chemical reaction is,
[tex]S^{2-}+Cr_2O_7^{2-}\rightarrow S+Cr^{3+}[/tex]
The oxidation-reduction half reaction will be :
Oxidation : [tex]S^{2-}\rightarrow S[/tex]
Reduction : [tex]Cr_2O_7^{2-}\rightarrow Cr^{3+}[/tex]
First balance the main element in the reaction.
Oxidation : [tex]S^{2-}\rightarrow S[/tex]
Reduction : [tex]Cr_2O_7^{2-}\rightarrow 2Cr^{3+}[/tex]
Now balance oxygen atom on both side.
Oxidation : [tex]S^{2-}\rightarrow S[/tex]
Reduction : [tex]Cr_2O_7^{2-}\rightarrow 2Cr^{3+}+7H_2O[/tex]
Now balance hydrogen atom on both side.
Oxidation : [tex]S^{2-}\rightarrow S[/tex]
Reduction : [tex]Cr_2O_7^{2-}+14H^+\rightarrow 2Cr^{3+}+7H_2O[/tex]
Now balance the charge.
Oxidation : [tex]S^{2-}\rightarrow S+2e^-[/tex]
Reduction : [tex]Cr_2O_7^{2-}+14H^++6e^-\rightarrow 2Cr^{3+}+7H_2O[/tex]
In order to balance the charge, we multiply oxidation reaction by 3. Thus, added both equation, we get the balanced redox reaction.
The balanced chemical equation in acidic medium will be,
[tex]3S^{2-}+Cr_2O_7^{2-}+14H^+\rightarrow 3S+2Cr^{3+}+7H_2O[/tex]
From the balanced chemical equation we conclude that, the number of moles of [tex]H^+[/tex] consumed from every mole of [tex]Cr_2O_7^{2-}[/tex] are 14 moles.
Hence. the correct option is, (E) 14
Select all of the following statements that are incorrect. A. Solids, liquids, and gases are all able to act as solutes in a solution. B. Solids, liquids, and gases are all able to act as solvents in a solution. C. Solids are not able to act as a solvent if a gas is the solute. D. Gases are not able to act as a solvent if a solid is the solute.
Answer:
B
Explanation:
Explanation:
Adsorption is defined as a process in which gas molecules tend to adsorb on the surface of a solid solvent.
Therefore, the statement solids are not able to act as a solvent if a gas is the solute, is false.
On the other hand, gases can also act as a solvent if a solid is the solute.
For example, air present in the surrounding acts as a solvent and solid substances present in the surrounding acts as a solute.
Hence, the statement gases are not able to act as a solvent if a solid is the solute, is false.
Thus, we can conclude that following are the statements which are incorrect.
Solids are not able to act as a solvent if a gas is the solute. Gases are not able to act as a solvent if a solid is the solute.The process where bacteria takes nitrogen out of the air and makes it usable for other organisms is called
Answer:
The process is called Nitrogen fixation
Explanation:
The nitrogen fixation is a process carried out by some prokaryotic microorganisms (bacteria), specifically those have the presence of the nitrogenase enzyme. The bacteria absorb the atmospheric nitrogen (N2) from the roots of plants, and the nitrogenase enzyme, with the help of two proteins that act as electron donors and acceptors (nitrogenase complex) reduce the nitrogen to ammonia (NH3), then the ammonia is ionized to NH4+ (ammonium). Followed by that, the ammonia is oxidated to nitrates and nitrites, which are finally absorbed again by plants.
How many moles of aluminum metal are required to produce 4.04 L of hydrogen gas at 1.11 atm and 27 °C by reaction with HCl?
2 Al(s) + 6 HCl(aq) → 2 AlCl3 (aq) + 3 H2(g)
Answer:
0.121 moles of aluminum metal are required to produce 4.04 L of hydrogen gas at 1.11 atm and 27 °C by reaction with HCl
Explanation:
This is the reaction:
2 Al(s) + 6 HCl(aq) → 2 AlCl₃ (aq) + 3 H₂(g)
To make 3 moles of H₂, we need 2 moles of Al.
By conditions given, we will find out how many moles of H₂ do we have.
Let's use the Ideal Gas Law
P. V = n . R . T
1.11 atm . 4.04L = n . 0.082 L.atm/mol.K . 300K
(1.11 atm . 4.04L) / (0.082 mol.K/L.atm . 300K) = n
0.182 mol = n
So the rule of three will be:
If 3 moles of H₂ came from 2 moles of Al
0.182 moles of H₂ will come from x
(0.182 .2) / 3 = 0.121 moles
A one or two letter abbreviation for a chemical element. True or false
Answer:
True
Explanation:
All the chemical elements have their abbreviations as one or two letters
The first letter in the abbreviation is a capital letter and the second letter is always a small letter
Majority of abbreviations are based on their english names
Final answer:
The statement regarding a chemical symbol being a one- or two-letter abbreviation for a chemical element is true. These symbols are a shorthand for elements, such as 'O' for oxygen or 'Fe' for iron, and are crucial for anyone studying chemistry.
Explanation:
The statement that a chemical symbol is a one- or two-letter abbreviation for a chemical element is true. Chemical symbols provide a concise way to represent elements in scientific writings and discussions. For instance, the symbol 'O' stands for oxygen, while 'Zn' represents zinc. The first letter of a chemical symbol is always capitalized, and if there is a second letter, it is lowercase.
Elements that have been known for a long time often have symbols derived from their Latin names. For example, the symbol for iron is 'Fe', which comes from its Latin name 'ferrum'. It is important for those studying chemistry to become familiar with the chemical symbols of the elements, most of which you can find on the periodic table.
I have very good ability to conduct electricity. I am never found alorie in nature. When I combine with other elements, I usually give up my one valence electron. I am the only element in my group with a one-letter symbol.
Answer:
Potassium
Explanation:
The description here fits potassium. Potassium is not found alone in nature as it is very reactive. Hence, it tends to occur in relation with other elements because of its high reactivity.
Because it is stated that it gives up its single valence electron, this shows that it belongs to group one of the periodic table. We might be tempted to think hydrogen is the correct answer. But it is interesting to note that hydrogen is not even supposed to be placed in group one at all. It is only placed there for convenience
How many milliliters of water at 23 °C with a density of 1.00 g/mL must be mixed with 180 mL (about 6 oz) of coffee at 95 °C so that the resulting combination will have a temperature of 60 °C? Assume that coffee and water have the same density and the same specific heat.
Answer:
V H2O = 170.270 mL
Explanation:
QH2O ( heat gained) = Qcoffe ( heat ceded)⇒ Q = mCΔT
∴ m: mass (g)
∴ C: specific heat
assuming:
δ H2O = δ Coffe = 1.00 g/mLC H2O = C coffe = 4.186 J/°C.g....from literature⇒ Q coffe = (mcoffe)(C coffe)(60 - 95)
∴ m coffe = (180mL)(1.00 g/mL) = 180 g coffe
⇒ Q = (180g)(4.186 J/°C.g)(-35°C) = - 26371.8 J
⇒ Q H2O = 26371.8 J = (m)(4.186 J/°C.g)(60 - 23)
⇒ (26371.8 J)/(154.882 J/g) = m H2O
⇒ m H2O = 170.270 g
⇒ V H2O = (170.270 g)(mL/1.00g) = 170.270 mL
Enter your answer in the provided box.S(rhombic) + O2(g) → SO2(g) ΔHo rxn= −296.06 kJ/molS(monoclinic) + O2(g) → SO2(g) ΔHo rxn= −296.36 kJ/molcalculate the enthalpy change for the transformationS(rhombic) → S(monoclinic)(Monoclinic and rhombic are different allotropic forms of elemental sulfur.)_______kJ/mol
Answer: [tex]\Delta H^0=+0.3kJ/mol[/tex].
Explanation:
According to Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.
According to this law, the chemical equation can be treated as ordinary algebraic expression and can be added or subtracted to yield the required equation. That means the enthalpy change of the overall reaction is the sum of the enthalpy changes of the intermediate reactions.
[tex]S_{rhombic}+O_2(g)\rightarrow SO_2(g)[/tex] [tex]\Delta H^0_1=-296.06kJ[/tex] (1)
[tex]S_{monoclinic}+O_2(g)\rightarrow SO_2(g)/tex] [tex]\Delta H^0_2=-296.36kJ[/tex] (2)
The final reaction is:
[tex]S_{rhombic}\rightarrow S_{monoclinic}[/tex] [tex]\Delta H^0_3=?[/tex] (3)
By subtracting (1) and (2)
[tex]\Delta H^0_3=\Delta H^0_1-\Delta H^0_2=-296.06kJ-(-296.36kJ)=0.3kJ[/tex]
Hence the enthalpy change for the transformation S(rhombic) → S(monoclinic) is 0.3kJ
The enthalpy change for the transformation from rhombic sulfur to monoclinic sulfur is -0.30 kJ/mol.
The enthalpy change for the transformation S(rhombic) → S(monoclinic), we will use the enthalpy changes provided for the reactions involving sulfur and oxygen:
S(rhombic) + O₂(g) → SO₂(g) ΔHo rxn = −296.06 kJ/molS(monoclinic) + O₂(g) → SO₂(g) ΔHo rxn = −296.36 kJ/molGiven these values, the enthalpy change for the transformation from rhombic sulfur to monoclinic sulfur can be found as follows:
ΔH (transformation) = ΔHo(S(monoclinic) → SO₂) - ΔHo(S(rhombic) → SO₂)
Using the provided enthalpy changes:
ΔH (transformation) = -296.36 kJ/mol - (-296.06 kJ/mol)
ΔH (transformation) = -296.36 kJ/mol + 296.06 kJ/mol
ΔH (transformation) = -0.30 kJ/mol
The enthalpy change for the transformation S(rhombic) → S(monoclinic) is -0.30 kJ/mol.
Newton's 2nd Law says the acceleration of an object depends on its ______ and the amount of _______ acting on it.
Friction and inertia
Mass and force
Force and friction
Inertia and Gravity
Answer:
Newton's 2nd Law says the acceleration of an object depends on its mass and the amount of net force acting on it.
Explanation:
Definition of acceleration:
The acceleration is rate of change of velocity of an object with respect to time.
Formula:
a = Δv/Δt
a = acceleration
Δv = change in velocity
Δt = change in time
Units:
The unit of acceleration is m.s⁻².
Acceleration can also be determine through following formula,
F = m × a
a = F/m
This is the newton's second law:
"The acceleration of an object depends on its mass and the amount of net force acting on it"
The acceleration is depend directly on the force while inversely on the mass.
Answer:
Mass and Force
Explanation:
A sample of benzene was vaporized at 25◦C. When 37.5 kJ of heat was supplied, 95.0 g of the liquid benzene vaporized. What is the enthalpy of vaporization of benzene at 25◦C?
1. 30.8 kJ/mol
2. 13.4 kJ/mol
3. 43.0 kJ/mol
4. 6.09 kJ/mol
5. 25.6 kJ/mol
Answer:
Enthalpy of vaporization = 30.8 kj/mol
Explanation:
Given data:
Mass of benzene = 95.0 g
Heat evolved = 37.5 KJ
Enthalpy of vaporization = ?
Solution:
Molar mass of benzene = 78 g/mol
Number of moles = mass/ molar mass
Number of moles = 95 g/ 78 g/mol
Number of moles = 1.218 mol
Enthalpy of vaporization = 37.5 KJ/1.218 mol
Enthalpy of vaporization = 30.8 kj/mol
Final answer:
The enthalpy of vaporization of benzene at 25°C is calculated by dividing the heat energy supplied by the number of moles vaporized, resulting in 30.8 kJ/mol.
Explanation:
The enthalpy of vaporization of benzene at 25°C can be calculated using the amount of heat supplied and the mass of benzene vaporized. Here's a step-by-step explanation:
First, convert the mass of benzene to moles using its molar mass (78.11 g/mol for C6H6).
Divide the given heat energy by the number of moles to find the enthalpy of vaporization per mole.
The calculation is as follows:
Moles of benzene = 95.0 g / 78.11 g/mol = 1.2169 mol
Enthalpy of vaporization (ΔHvap) = 37.5 kJ / 1.2169 mol = 30.8 kJ/mol
The correct answer is 30.8 kJ/mol, which is option 1.
If a polypeptide synthesized by a ribosome contains 99 amino acids in the chain, how many codons (including the start and stop codons) were required on the mRNA to make the polypeptide chain?
Explanation:
-101 mRNA codons
In the genetic code, an amino acid is encoded by 3 nucleotides, while there are just 4 bases . Each amino acid is specifically encoded by a codon- a triplet sequence of nucleotides...
Thus 99 amino acids= 99 codon sequences.
...along with a start and stop codon, this would require 101 mRNA codons
Further Explanation:
The nucleic acids are comprised of smaller units called nucleotides and function as storage for the body’s genetic information. These monomers include ribonucleic acid (RNA) or deoxyribonucleic acid (DNA). They differ from other macromolecules since they don’t provide the body with energy. They exist solely to encode and protein synthesis.
Basic makeup: C, H, O, P; they contain phosphate group 5 carbon sugar does nitrogen bases which may contain single to double bond ring.
Codons are three nucleotide bases encoding an amino acid or signal at the beginning or end of protein synthesis.
RNA codons determine certain amino acids so the order in which the bases occur within in the codon sequence designates which amino acid is to be made bus with the four RNA nucleotides (Adenine, Cysteine and Uracil) Up to 64 codons (with 3 as stop codons) determine amino acid synthesis. The stop codons ( UAG UGA UAA) terminate amino acid/ protein synthesis while the start codon AUG begins protein synthesis.
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Dissolving 5.28 g of an impure sample of calcium carbonate in hydrochloric acid produced 1.14 L of carbon dioxide at 20.0 °C and 791 mmHg. Calculate the percent by mass of calcium carbonate in the sample.
Final answer:
To calculate the percent by mass of calcium carbonate in the sample, we need to determine the mass of calcium carbonate present in the 1.14 L of carbon dioxide produced. We can use the ideal gas law to calculate the moles of carbon dioxide, and then use stoichiometry to convert from moles of CO2 to moles of CaCO3. Finally, we can calculate the percent by mass of CaCO3 in the sample by dividing the mass of CaCO3 by the mass of the sample and multiplying by 100.
Explanation:
To calculate the percent by mass of calcium carbonate in the sample, we need to determine the mass of calcium carbonate present in the 1.14 L of carbon dioxide produced. We can use the ideal gas law to calculate the moles of carbon dioxide, and then use stoichiometry to convert from moles of CO2 to moles of CaCO3. Finally, we can calculate the percent by mass of CaCO3 in the sample by dividing the mass of CaCO3 by the mass of the sample and multiplying by 100.
First, let's calculate the moles of CO2 using the ideal gas law:
mass of CO2 = (volume of CO2) x (molar mass of CO2) = (1.14 L) x (22.4 g/mol) = 25.536 g
Next, let's calculate the moles of CaCO3 using stoichiometry. From the balanced equation CaCO3 + 2HCl → CaCl2 + H2O + CO2, we know that 1 mole of CaCO3 produces 1 mole of CO2. Therefore, moles of CaCO3 = moles of CO2 = 25.536 g / (molar mass of CaCO3) = 25.536 g / 100.09 g/mol = 0.255 mol
Finally, let's calculate the percent by mass of CaCO3:
percent by mass of CaCO3 = (mass of CaCO3 / mass of the sample) x 100 = (0.255 mol x (100.09 g/mol)) / 5.28 g x 100 = 4.85%
For water ∆H°vap = 40.7 kJ/mol at 100.°C, its boiling point. Calculate ∆S° for the vaporization of 1.00 mol water at 100.°C and 1.00 atm pressure.
Answer : The value of change in entropy for vaporization of water is [tex]1.09\times 10^2J/mol[/tex]
Explanation :
Formula used :
[tex]\Delta S^o=\frac{\Delta H^o_{vap}}{T_b}[/tex]
where,
[tex]\Delta S^o[/tex] = change in entropy of vaporization = ?
[tex]\Delta H^o_{vap}[/tex] = change in enthalpy of vaporization = 40.7 kJ/mol
[tex]T_b[/tex] = boiling point temperature of water = [tex]100^oC=273+100=373K[/tex]
Now put all the given values in the above formula, we get:
[tex]\Delta S^o=\frac{\Delta H^o_{vap}}{T_b}[/tex]
[tex]\Delta S^o=\frac{40.7kJ/mol}{373K}[/tex]
[tex]\Delta S^o=1.09\times 10^2J/mol[/tex]
Therefore, the value of change in entropy for vaporization of water is [tex]1.09\times 10^2J/mol[/tex]
The entropy change ∆S° for the vaporization of 1.00 mol of water at its boiling point is calculated to be 109.09 J/K·mol using the given enthalpy of vaporization.
Explanation:To calculate ∆S° for the vaporization of 1.00 mol water at 100.°C and 1.00 atm pressure when ∆H°vap = 40.7 kJ/mol, we can use the thermodynamic relation ∆G° = ∆H° - T∆S° and the fact that at the boiling point, ∆G° for the phase change is zero. This would mean the ∆S° can be calculated as ∆S° = ∆H°vap/T. Plugging in the known values,
∆S° = 40.7 kJ/mol / 373.15 K
∆S° = 0.10909 kJ/K·mol
Since 1 kJ = 1000 J, we convert this to J:
∆S° = 109.09 J/K·mol
Therefore, the entropy change ∆S° for the vaporization of 1.00 mol of water at its boiling point is 109.09 J/K·mol.
The flashing of fireflies is the result of a chemical reaction, and the rate of flashing can be described by the Arrhenius equation. A certain batch of fireflies were observed to flash at a rate of 17.0 times per minute at 25°C and at a rate of 5.0 times per minute at 15°C. Use these data to find the apparent activation energy for the reaction that causes the flies to flash.
Answer:
-87.4 kJ/mol
Explanation:
We can rewrite Arrhenius' equation as:
ln(k₂/k₁) = -Ea/R * (1/T₂ - 1/T₁)
Where k₂ and k₁ are the rates of the reaction at temperatures T₂ and T₁, Ea is the activation energy and R is the universal gas constant.
For this problem:
k₂ = 5
k₁ = 17
T₂ = 15°C = 288.16 K
T₁ = 25°C = 298.16 K
R = 8.314 J/mol·K
We put the data in the equation and solve for Ea:
ln(5/17) = -Ea/8.314 J/mol·K * (1/288.16K - 1/298.16K)
-1.224 = -Ea/8.314 J/mol·K * 1.1639x10⁻⁴K⁻¹
Ea = -87416.78 J/mol ≅ -87.4 kJ/mol
Each molecule of hemoglobin combines with four molecule of oxygen in order to transport oxygen throughout the body. It is observed that 1.51 g of hemoglobin combines with 2.30 mL of O 2 at 37 °C and 743 torr. What is the molar mass of hemoglobin?
Answer:
68325.8 g/mol
Explanation:
Given that:
Pressure = 743 torr
Temperature = 37 °C
The conversion of T( °C) to T(K) is shown below:
T(K) = T( °C) + 273.15
So,
T = (37 + 273.15) K = 310.15 K
T = 310.15 K
Volume = 2.30 mL = 0.00230 L ( 1 mL = 0.001 L)
Using ideal gas equation as:
PV=nRT
where,
P is the pressure
V is the volume
n is the number of moles
T is the temperature
R is Gas constant having value = 62.364 L.torr/K.mol
Applying the equation as:
743 torr × 0.00230 L = n × 62.364 L.torr/K.mol × 310.15 K
⇒n = 8.84 × 10⁻⁵ moles
Since, given that:-
4 moles of oxygen gas is transferred by 1 mole of haemoglobin.
8.84 × 10⁻⁵ moles of oxygen gas is transferred by 8.84 × 10⁻⁵/4 moles of haemoglobin.
Moles of haemoglobin = 2.21 × 10⁻⁵ moles
Mass = 1.51 g
The formula for the calculation of moles is shown below:
[tex]moles = \frac{Mass\ taken}{Molar\ mass}[/tex]
Thus,
[tex]2.21\times 10^{-5}\ mol= \frac{1.51\ g}{Molar\ mass}[/tex]
[tex]Molar\ mass= 68325.8\ g/mol[/tex]
The question is asking for the molar mass of hemoglobin, which can be calculated using the Ideal Gas Law and the information provided. Hemoglobin, a protein in red blood cells, combines with four oxygen molecules, the fact that is fundamental to this calculation.
Explanation:The molar mass of hemoglobin can be calculated using the Ideal Gas Law (PV=nRT). In this case, the volume of O2 (V) is 2.30 mL or 0.0023 L, the pressure (P) is 743 torr (or approximately 0.977 atm), the gas constant (R) is 0.0821 L⋅atm/mol⋅K, and the temperature (T) is 37 °C or 310 K. We can solve this equation to find the amount of moles of O2 (n). As each molecule of hemoglobin combines with four molecules of O2, we can then find out the amount of moles of hemoglobin, and knowing its mass (1.51 g), finally calculate its molar mass (grams per mole).
To confirm the correctness of this procedure, remember that hemoglobin is a protein found in red blood cells which combines with what? Oxygen molecules - four of them, in fact! This is crucial for the transport of oxygen throughout the body, and it also directly pertains to and informs our calculation of hemoglobin's molar mass.
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A 2.85-g sample of an unknown chlorofluorocarbon is decomposed and produces 564 mL of chlorine gas (Cl2) at a pressure of 752 mmHg and a temperature of 298 K. What is the percent chlorine (by mass) in the unknown chlorofluorocarbon
The percentage of chlorine by mass in the unknown chlorofluorocarbon is 56.8%
We'll begin by calculating the number of mole of Cl₂ produced using the ideal gas equation as illustrated below:
Volume (V) = 564 mL = 564 / 1000 = 0.564 LPressure (P) = 752 mmHg = 752 / 760 = 0.989 atmTemperature (T) = 298 KGas constant (R) = 0.0821 atm.L/KmolNumber of mole (n) =?PV = nRT
0.989 × 0.564 = n × 0.0821 × 298
0.557796 = n × 24.4658
Divide both side by 24.4658
n = 0.557796 / 24.4658
n = 0.0228 mole
Next, we shall determine the mass of 0.0228 mole of Cl₂
Mole = 0.0228 moleMolar mass of Cl₂ = 2 × 35.5 = 71 g/molMass of Cl₂ =?Mass = mole × molar mass
Mass of Cl₂ = 0.0228 × 71
Mass of Cl₂ = 1.62 g
Finally, we shall determine the percentage of chlorine in the unknown chlorofluorocarbon.
Mass of Cl₂ = 1.62 gMass of compound = 2.85 gPercentage of chlorine =?Percentage = (mass / total mass) × 100
Percentage of chlorine =(1.62 / 2.85) × 100
Percentage of chlorine = 56.8%
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The percent chlorine (by mass) in the unknown chlorofluorocarbon is 0%.
Explanation:In order to determine the percent chlorine (by mass) in the unknown chlorofluorocarbon, we need to calculate the mass of chlorine gas produced from the 2.85-g sample. From the equation 2.5g H and 7.5g C make up a 10.0g sample, we can calculate the percent composition of hydrogen and carbon to be 25% and 75%, respectively.
Knowing the percent composition of hydrogen and carbon, we can assume that the unknown chlorofluorocarbon consists of only hydrogen, carbon, and chlorine. Since chlorine gas is produced when the unknown chlorofluorocarbon is decomposed, the percent chlorine (by mass) can be calculated by subtracting the percent composition of hydrogen and carbon from 100%. Therefore, the percent chlorine is 100% - (25% + 75%) = 0%.
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Be sure to answer all parts. Write the equations representing the following processes. In each case, be sure to indicate the physical state of the ions. 1. The electron affinity of S⁻:
2. The third ionization energy of titanium:
3. The electron affinity of Mg²⁺:
4. The ionization energy of O²⁻:
Answer:
1.[tex]S^{-}(g)+e^{-} \rightarrow S^{2-}(g)[/tex]
2.[tex]Ti^{2+}(g) \rightarrow Ti^{3+}(g) \,\, IE = 2652.5\,kJ.mol^{-1}[/tex]
3.The electron affinity of [tex]Mg^{2+}[/tex] is zero.
4.[tex]O^{2-}(g) \rightarrow O^{-}(g)+e^{-}[/tex]
Explanation:
1.
Electron affinity:
It is defined as the amount of energy change when an electron is added to atom in the gaseous phase.
The electron affinity of [tex]S^{-}[/tex] is as follows.
[tex]S^{-}(g)+e^{-} \rightarrow S^{2-}(g)[/tex]
2.
Ionization energy:
Amount of energy required to removal of an electron from an isolated gaseous atom.
The third ionization energy of Titanium is as follows.
[tex]Ti^{2+}(g) \rightarrow Ti^{3+}(g) \,\, IE = 2652.5\,kJ.mol^{-1}[/tex]
3.
The electronic configuration of Mg: [tex]1s^{2}2s^{2}2p^{6}3s^{2}[/tex]
By the removal of two electrons from a magnesium element we get [tex]Mg^{2+}[/tex] ion.
[tex]Mg^{2+}[/tex] has inert gas configuration i.e,[tex]1s^{2}2s^{2}2p^{6}[/tex]
Hence, it does not require more electrons to get stability.
Therefore,the electron affinity of [tex]Mg^{2+}[/tex] is zero.
4.
The ionization energy of [tex]O^{2-}[/tex] is follows.
[tex]O^{2-}(g) \rightarrow O^{-}(g)+e^{-}[/tex]
The electron affinity equation for S⁻ is S⁻(g) + e⁻ → S²⁻(g). The third ionization energy equation for titanium is Ti²⁺(g) → Ti³⁺(g) + e⁻. The equation representing the electron affinity of Mg²⁺ is Mg²⁺(g) + e⁻ → Mg³⁺(g). The ionization energy equation for O²⁻ is O²⁻(g) → O³⁻(g) + e⁻.
Explanation:1. The electron affinity of S⁻: The electron affinity represents the energy change that occurs when an electron is added to a neutral atom or ion. For sulfur (S⁻), the equation representing this process is: S⁻(g) + e⁻ → S²⁻(g). Here, the physical state of S⁻ and S²⁻ is gas.
2. The third ionization energy of titanium: Ionization energy is the energy required to remove an electron from an atom or ion. For titanium, the equation representing the third ionization energy is: Ti²⁺(g) → Ti³⁺(g) + e⁻. The physical state of Ti²⁺ and Ti³⁺ is gas.
3. The electron affinity of Mg²⁺: The electron affinity of a cation, such as Mg²⁺, is the energy change when an electron is added to the cation. Here, the equation representing this process is: Mg²⁺(g) + e⁻ → Mg³⁺(g). The physical state of Mg²⁺ and Mg³⁺ is gas.
4. The ionization energy of O²⁻: Ionization energy is the energy required to remove an electron from an atom or ion. For oxygen, the equation representing the ionization energy of O²⁻ is: O²⁻(g) → O³⁻(g) + e⁻. The physical state of O²⁻ and O³⁻ is gas.
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Which set of chemical name and chemical formula for the same compound is correct?
A) Ammonium sulfite (NH4)2S
B) Iron(lll) phosphate, FePO4
C) lithium carbonate, LiCO3
D) magnesium dichromate, MgCrO4
Answer:
B) Iron(lll) phosphate, FePO4
Option.B-Iron(lll) phosphate, FePO4 is the correct answer.
A monoclinic crystal powder with the chemical formula FePO4, ferric phosphate is sometimes referred to as ferric phosphate and ferric orthophosphate.
Chemical Formula and Chemical name of Iron(lll) phosphate, FePO4With the chemical formula FePO4, iron(III) phosphate, commonly known as ferric phosphate, is an inorganic substance.Four polymorphs of FePO4 and two polymorphs of the dihydrate FePO4(H2O)2 are two examples of related materials.These materials are found in the mineral world and have minimal technical uses.The most prevalent type of FePO4 adopts a -quartz structure. As a result, the substance comprises of phosphate and tetrahedral Fe(III) sites.As a result, the molecular geometry of the P and Fe is tetrahedral. A phase shift to a denser structure with octahedral Fe centers takes place at high pressures.Additionally known are two orthorhombic structures and a monoclinic phase.The Fe center is octahedral with two cis water ligands in the two polymorphs of the dihydrate.In the production of steel and metals, iron(III) phosphate can be employed. Iron phosphate stops further metal oxidation when it is adhered to a surface made of metal.The iron pillar of Delhi's resistance to corrosion is in part due to its existence.In order to promote adhesion to the iron or steel substrate and avoid corrosion, which can result in the premature failure of following coating processes, iron phosphate coatings are frequently used as a pre-treatment for painting or powder coating.Additionally, it can be applied to surfaces made of iron or steel to bond textiles, wood, and other materials.To know more about similar question click here-
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A geological sample is found to have a Pb-206/U-238 mass ratio of 0.337/1.00. Assuming there was no Pb-206 present when the sample was formed, how old is it? The half-life of U-238 is 4.5 × 109 years.
Answer:
[tex]Age=2.52*10^9 years[/tex]
Explanation:
To determine the age, we need to know how much U have become Pb, so first we have to calculate the Pb moles present in a sample:
[tex]n_{Pb}=\frac{0.337g}{206g/mol}=0.00164 mol[/tex]
[tex]n_{U}=\frac{1 g}{238g/mol}=0.0042 mol[/tex]
The percentage of U degradation:
[tex]P=\frac{n_{Pb}}{n_{Pb}+n_{U}}[/tex]
[tex]P=\frac{0.00164}{0.00164+0.0042}=0.28[/tex]
Assuming that the life time is linear:
[tex]Age=\frac{4.5*10^9 years}{0.5 life time}*0.28 life time[/tex]
[tex]Age=2.52*10^9 years[/tex]
Answer:
7.1 x 10^9 years
Explanation:
This is the answer according to Mastering Chemistry.
Find an expression for the change in entropy when two blocks of the same substance of equal mass, one at the temperature Th and the other at Tc, are brought into contact and allowed to reach equilibrium. Evaluate the change for the two blocks of copper, each of mass 500 grams with Cpcm= 24.4 J KT-1 mol-1, taking Th = 500 K and Tc = 250 K.
Explanation:
Relation between entropy change and specific heat is as follows.
[tex]\Delta S = C_{p} log (\frac{T_{2}}{T_{1}})[/tex]
The given data is as follows.
mass = 500 g, [tex]C_{p}[/tex] = 24.4 J/mol K
[tex]T_{h}[/tex] = 500 K, [tex]T_{c}[/tex] = 250 K
Mass number of copper = 63.54 g /mol
Number of moles = [tex]\frac{mass}{/text{\molar mass}}[/tex]
= [tex]\frac{500}{63.54}[/tex]
= 7.86 moles
Now, equating the entropy change for both the substances as follows.
[tex]7.86 \times 24.4 \times [T_{f} - 250][/tex] = [tex]7.86 \times 24.4 \times [500 -T_{f}][/tex]
[tex]T_{f} - 250 = 500 - T_{f}[/tex]
[tex]2T_{f}[/tex] = 750
So, [tex]T_{f}[/tex] = [tex]375^{o}C[/tex]
For the metal block A, change in entropy is as follows.[tex]\Delta S = C_{p} log (\frac{T_{2}}{T_{1}})[/tex]
= [tex]24.4 log [\frac{375}{500}][/tex]
= -3.04 J/ K mol
For the block B, change in entropy is as follows.[tex]\Delta S = C_{p} log (\frac{T_{2}}{T_{1}})[/tex]
= [tex]24.4 log [\frac{375}{250}][/tex]
= 4.296 J/Kmol
And, total entropy change will be as follows.
= 4.296 + (-3.04)
= 1.256 J/Kmol
Thus, we can conclude that change in entropy of block A is -3.04 J/ K mol and change in entropy of block B is 4.296 J/Kmol.
For the reaction, calculate how many grams of the product form when 14.4 g of Br2 completely reacts. Assume that there is more than enough of the other reactant. 2K(s)+Br2(l)→2KBr(s)
Answer:
The answer to your question is 21.45 g of KBr
Explanation:
Chemical reaction
2K + Br₂ ⇒ 2KBr
14.4 ?
Process
1.- Calculate the molecular mass of bromine and potassium bromide
Bromine = 2 x 79.9 = 159.8g
Potassium bromide = 2(79.9 + 39.1) = 238 g
2.- Solve it using proportions
159.8 g of Bromine ------------ 238 g of potassium bromide
14.4 g of Bromine ------------ x
x = (14.4 x 238) / 159.8
x = 3427.2 / 159.8
x = 21.45g of KBr
The following sets of quantum numbers, listed in the order n, l, ml, and ms were written for the last electrons added to an atom. Identify which sets are valid and classify the others by the rule or principle that is violated.
choices for these answers are: "other violation," "pauli violation," and "valid."
a. 5 0 0 +1/2
5 0 0 -1/2
b. 4 1 -1 +1/2
4 1 0 +1/2
4 1 +1 +1/2
c. 3 2 -1 +1/2
3 2 0 +1/2
3 2 +1 +1/2
3 2 0 +1/2
3 2 +2 +1/2
d. 3 1 -1 +1/2
3 1 0 +1/2
3 3 +1 +1/2
Answer:
a. 5 0 0 +1/2
5 0 0 -1/2
Valid
b. 4 1 -1 +1/2
4 1 0 +1/2
4 1 +1 +1/2
Valid
c. 3 2 -1 +1/2
3 2 0 +1/2
3 2 +1 +1/2
3 2 0 +1/2
3 2 +2 +1/2
Pauli violation
d. 3 1 -1 +1/2
3 1 0 +1/2
3 3 +1 +1/2
other violation
Explanation:
The four quantum number and possible values are:
n = 1,2,3.....
l = 0 , (n-1), (n-2).....
m = +l , 0 , -l
s = [tex]+\frac{1}{2}[/tex] or [tex]-\frac{1}{2}[/tex]
Pauli's exclusion principle: No two electrons in an atom can have all the four quantum numbers same.
Let us check each case:
a. 5 0 0 +1/2
5 0 0 -1/2
Valid
b. 4 1 -1 +1/2
4 1 0 +1/2
4 1 +1 +1/2
Valid
c. 3 2 -1 +1/2
3 2 0 +1/2
3 2 +1 +1/2
3 2 0 +1/2
3 2 +2 +1/2
Pauli violation
The two electrons have same four quantum numbers
3 2 0 +1/2
3 2 0 +1/2
d. 3 1 -1 +1/2
3 1 0 +1/2
3 3 +1 +1/2
other violation
As mentioned above in the condition the value of "l" can be only less than "n"
So for 3 3 +1 +1/2 : n = 3 and l= 3, which is not valid.
The arrangement of electrons in orbitals are showed by four sets of quantum numbers.
According to the Pauli exclusion theory, no two electrons in an atom should have all the four quantum numbers as the same. According to this principle, the spin quantum number of electrons in an atom must differ even if they are in the same orbital.
For the first set;
5 0 0 +1/2
5 0 0 -1/2
This set, correctly corresponds to the 5s orbital so it is valid.
For the second set;
4 1 -1 +1/2
4 1 0 +1/2
4 1 +1 +1/2
This should have corresponding to the 4p orbital so it is valid.
For the third set;
3 2 -1 +1/2
3 2 0 +1/2
3 2 +1 +1/2
3 2 0 +1/2
3 2 +2 +1/2
This set should correspond to a 3d orbital but we can see that are two electrons in the set that has exactly the same quantum numbers of 3 2 0 +1/2. This violates the Pauli exclusion theory so we should mark "Pauli violation".
For the fourth set:
3 1 -1 +1/2
3 1 0 +1/2
3 3 +1 +1/2
This set should have corresponded to a 3p orbital but remember that the values of l only range from 0 to (n - 1). This means that we can not have n =3, l=3 so the arrangement 3 3 +1 +1/2 is not possible. We should mark "other violation".
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The total energy of all the particles in a substance is called
Answer:
Internal energy
Explanation:
Particles have two main energies that scientists acknowledge.
The energy that is associated with their movement which we call kinetic energy. It is worth noting that particles have different kinetic energy, however the average kinetic energy that they have is directly proportional to temperature.The energy that is due to the interactive forces (attraction or repulsion) between particles is called potential energyWhen these two types of energies are considered collectively, we call that internal energy
A 17.55 mL solution of potassium nitrate (KNO3) was diluted to 125.0 mL, and 25.00 mL of this solution was then diluted to 1.000 × 103 mL. The concentration of the final solution is 0.00383 M. Calculate the concentration of the original solution.
Answer:
[tex]M_2 = 1.094 M[/tex]
Explanation:
Given data:
V1 = 25.0 ml
M2 = 0.00383 M
V2 = 1000 ml
we knwo that [tex]M_1 V_1 = M_2 V_2[/tex]
∴ [tex]M_1 = \frac{M_2 V_ 2}{V_1}[/tex]
[tex] = \frac{0.00383 M \times 1000}{25.0}[/tex]
= 0.1532 M
0.1532 M is concentration in 25 ml but taken from 125 ml solution.
∴ The concentration in 125.0 ml solution is = 0.1532 M
M1 = 0.1532 M
V1 = 125.0ml and V2 = 17.5.0ml
[tex]M_2 = \frac{M_1 V_1}{V_2}[/tex]
[tex] = \frac{0.1532 M \times 125.0}{17.5}[/tex]
[tex]M_2 = 1.094 M[/tex]
Refrigerators are usually kept at about 5°C, while room temperature is about 20°C. if you were to take an empty sealed 2 liter soda bottle at room temperature and place it in the fridge, would you expect it to contact to one fourth it's original volume? options.
(a) yes, because 5 is one fourth of 20.
(b) No, because there is no gas inside the bottle.
(c) No, because Celsius is not an absolute temperature scale.
Answer:
c) No, because Celsius is not an absolute temperature scale
Explanation:
converting 5 oC to kelvin which is the absolute temperature scale gives = 273 + 5 = 278 K
and converting 20 oC to kelvin = 20 + 273 = 293 K
the ratio = 278 / 293 = 0.94 approx 1 not 4