Why might an idea or hypothesis be discarded? A. If another scientist doesn't like it. B. If evidence also supports another hypothesis. C. If it is tested and the evidence does not support it. D. If a politician disagrees with it.

Answer:

According to Le Chatelier’s Principle, a stress placed on a system at equilibrium will cause the equilibrium to shift to counteract the stress.  For example, a temperature increase in the above reaction will favor the reverse reaction to use the excess heat and form brown NO2 gas.  A temperature decrease in the above reaction favors the forward reaction to produce heat and form colorless N2O4 gas.

Answer:

The equilibrium shifts to the left and more of NO₂ is formed.

Explanation:

The Le Chatelier's principle states that when a form of stress is applied to a system in equilibrium, the system shifts so as to relieve that stress.

This principle explains that addition of one of the reactants to a system in equilibrium leads to the equilibrium shifting in such a way that the reaction occurring reduces the concentration of the added reactant.

In this case the addition of dinitrogen tetraoxide increases its concentration and therefore equilibrium shifts to reduce this concentration.

Answer:

Explanation:

Formula

density = mass / volume

Givens

mass = 26.94

volume = 2.568

Solution

density = 26.94 / 2.568

density = 10.49 grams / cc^3

Answer

This is very likely silver.

The givens in the  table except for the first 2 are wrong.

silver is as above

copper is a bit over 8.

Answer: The given material is silver.

Explanation:

To calculate density of a substance, we use the equation:

[tex]\text{Density of substance}=\frac{\text{Mass of substance}}{\text{Volume of substance}}[/tex]

We are given:

Mass of object = 26.94 g

Volume of object = [tex]2.568cm^3[/tex]

Putting values in above equation, we get:

[tex]\text{Density of object}=\frac{26.94g}{2.568cm^3}=10.49g/cm^3[/tex]

The calculated value of density corresponds to the density of silver.

Hence, the given material is silver.

Answer:

The final temperature of the combined metals is 49.2314 °C

Explanation:

Heat gain by gold = Heat lost by iron

Thus,  

[tex]m_{gold}\times C_{gold}\times (T_f-T_i)=-m_{iron}\times C_{iron}\times (T_f-T_i)[/tex]

Where, negative sign signifies heat loss

Or,  

[tex]m_{gold}\times C_{gold}\times (T_f-T_i)=m_{iron}\times C_{iron}\times (T_i-T_f)[/tex]

For gold:

Mass = 11.4 g

Initial temperature = 14.5 °C

Specific heat of gold = 0.129 J/g°C

For iron:

Mass = 18.4 kg

Initial temperature = 55.4 °C

Specific heat of water = 0.450 J/g°C

So,

[tex]11.4\times 0.129\times (T_f-14.5)=18.4\times 0.450\times (55.4-T_f)[/tex]

[tex]1.4706\times (T_f-14.5)=8.28\times (55.4-T_f)[/tex]

[tex]1.4706\times T_f-1.4706\times 14.5=8.28\times 55.4-8.28\times T_f[/tex]

[tex]1.4706\times T_f-21.3237=458.712-8.28\times T_f[/tex]

[tex]1.4706\times T_f+8.28\times T_f=458.712+21.3237[/tex]

[tex]T_f=49.2314[/tex]

Thus,

The final temperature of the combined metals is 49.2314 °C

The final temperature of the combined metals is approximately 49.31°C.

Given data:

Step 1: Calculate the heat gained/lost by each metal

Step 2: Set up the equation

Step 3: Solve for T_f

And there you have it! The final temperature of the combined metals is approximately 49.31°C.

Final answer:

The heat of reaction for the combustion of a mole of titanium in this calorimeter is 15220 kJ/mol.

Explanation:

In order to calculate the heat of reaction for the combustion of a mole of Ti in this calorimeter, we need to use the equation q = mcΔT. First, we need to calculate the amount of heat absorbed by the calorimeter and its contents.

The heat capacity of the calorimeter is given as 9.84 kJ/K, and the temperature change is 91.60°C - 25.00°C = 66.60°C. Therefore, the heat absorbed by the calorimeter and its contents is:

q = (9.84 kJ/K)(66.60°C) = 654.24 kJ.

Next, we need to determine the amount of moles in 2.060 g of titanium. The molar mass of titanium is 47.867 g/mol, so:

moles of titanium = 2.060 g / 47.867 g/mol = 0.043 moles.

Finally, we can calculate the heat of reaction for the combustion of a mole of Ti:

heat of reaction = 654.24 kJ / 0.043 moles = 15220 kJ/mol.

Answer:

Gay-Lussac's law, Amontons' law or the pressure law was found by Joseph Louis Gay-Lussac in 1809.

Explanation:

It states that, for a given mass and constant volume of an ideal gas, the pressure exerted on the sides of its container is directly proportional to its absolute temperature.

Answer:

Gay-Lussac's law

Explanation:

Gay-Lussac's second law, which is called isochoric transformation or isovolumetric transformation, is related to the behavior of gases when subjected to a constant volume. The elaboration of this law was attended by the French scientist Jacques Alexandre Cesar Charles.

According to Lussac, when a gas is placed in a container at a constant volume, it is found that if a pressure is exerted on that gas, a proportional increase in the absolute temperature of that gas will occur.

Generally, under Gay-Lussac law, a gas's pressure and temperature will always be directly proportional as long as the volume is constant. Thus, increasing the pressure increases the temperature; decreasing the pressure decreases the temperature.

Answer:

12 L of 40% sulfuric acid solution and 8 L of 10% sulfuric acid solution are needed to make 20 L of sulfuric acid solution.

Explanation:

For first solution of sulfuric acid :

C₁ = 40% , V₁ = ?

For second solution of sulfuric acid :

C₂ = 10% , V₂ = ?

For the resultant solution of sulfuric acid:

C₃ = 28% , V₃ = 20L

Also,

V₁ + V₂ = V₃ = 20L ......................................(1)

Using

C₁V₁ + C₂V₂ = C₃V₃

40×V₁ + 10×V₂ = 28×20

So,

40V₁ + 10V₂ = 560........................................(2)

Solving 1 and 2 as:

V₂ = 20 - V₁

Applying in 2

40V₁ + 10(20 - V₁)  = 560

40V₁ + 200 - 10V₁ = 560

30V₁ = 360

V₁ = 12 L

So,

V₂ = 20 - V₁ = 8L

12 L of 40% sulfuric acid solution and 8 L of 10% sulfuric acid solution are needed to make 20 L of sulfuric acid solution.

Answer:

Percent ionic character is defined as the ratio of a bond’s actual dipole moment to the dipole moment it would have if the electron were completely transferred from one atom to the other, multiplied by 100

Explanation:

The percent ionic character seeks to establish the amount of electrovalency in a particular compound. It simply compares the covalency i.e extent of shared electrons to the the electrons that are transferred.

It is given as the ratio of the acutal dipole moment to the dipole moment due to ionic character of the bond multiplied by 100:

Percent ionic character = μ_obs/μ_ionic x 100

Where μobs is the actual dipole moment and μ ionic is the dipole moment if the bonds were 100% ionic.

Answer:

Explanation:

Given parameters:

Mass of ionic compound = 0.3257g

Mass of AgBr precipitate = 0.7165g

Unknown:

Percent mass of Br in the original compound.

Solution

The percent mass of Br in original compound = [tex]\frac{mass of  Br  in the sample}{mass of sample}[/tex]

Now we have to find the mass of Br⁻:

We must note that the same mass of Br⁻ would move through the ionic sample to form the precipitate.

Mass of Br in AgBr = [tex]\frac{Atomic mass of Br}{Molar mass of AgBr}  x mass of precipitate[/tex]

Mass of Br =  [tex]\frac{80}{80 + 108}[/tex]  x 0.7165

Mass of Br = 0.426 x 0.7165 = 0.305g

Percent mass of Br = [tex]\frac{0.305}{0.3257}[/tex] x 100 = 93.7%

Answer:

Stable

Explanation:

An unstable star wouldn't stay the same, a dying star would decrease in size, and a protostar would increase in size.

A star is stable when its size remains constant over time.

An astronomical object known as a star has been made up of a bright plasma spheroid that would be held together using gravity.

Time is just the ongoing progression of existence and things that happen in what seems to be an irrevocable order from the past, present, and forward into the future.

A star is stable when its size remains constant over time.

To know more about time and star.

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Answer:

CH₄ < CH₃Cl < CH₃OH

Explanation:

In all three compounds, the central C atom has four bonds, so the molecules all have a tetrahedral molecular geometry.

The only difference is in one bond:  CH₃-Cl, CH₃-H, and CH₃-OH.

CH₃-Cl: The C-Cl bond is polar, so the strongest intermolecular forces are dipole-dipole.

CH₄: the molecule is symmetrical, so the strongest intermolecular forces are London dispersion forces.

CH₃-OH: The OH group can form hydrogen bonds.

The order of strength of intermolecular forces is

London dispersion forces < dipole-dipole < hydrogen bonds

The order of boiling points is

CH₄ < CH₃Cl < CH₃OH

The boiling points of compounds CH3Cl, CH4, and CH3OH increase in the order CH4, CH3Cl, and CH3OH due to the increasing strength of intermolecular forces namely London dispersion forces, dipole-dipole interactions, and hydrogen bonding, respectively.

The boiling points of these compounds, CH3Cl, CH4, and CH3OH, vary due to their different types of intermolecular forces. Methane (CH4) is a nonpolar molecule that only has London dispersion forces, therefore, it is expected to have the lowest boiling point. Chloromethane (CH3Cl) is slightly polar due to the large electronegativity difference between Carbon and Chlorine, and it will have stronger London dispersion forces than CH4 as well as minor dipole-dipole interactions, giving it a higher boiling point than CH4. Methanol (CH3OH) has the strongest intermolecular forces due to the presence of hydrogen bonding. Therefore, CH3OH is expected to have the highest boiling point. The ordering from lowest to highest boiling point is therefore CH4 < CH3Cl < CH3OH.

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Answer :

(a) The concentration of hydrogen ion and hydroxide ion are, [tex]1.708\times 10^{-7}M[/tex].

(b) The pH of pure water is, 6.78

(c) The pH of solution is, 13

Explanation :

(a) First we have to calculate the concentration of hydrogen ion and hydroxide ion.

As we know that,

[tex]K_w=[H^+][OH^-][/tex]

In pure water, the concentration of hydrogen ion and hydroxide ion are equal. So, let the concentration of hydroxide ion and hydrogen ion be, 'x'.

[tex]2.92\times 10^{-14}=(x)\times (x)[/tex]

[tex]2.92\times 10^{-14}=(x)^2[/tex]

[tex]x=1.708\times 10^{-7}M[/tex]

The concentration of hydrogen ion and hydroxide ion are, [tex]1.708\times 10^{-7}M[/tex].

(b) Now we have to calculate the pH of pure water.

[tex]pH=-\log [H^+][/tex]

[tex]pH=-\log (1.708\times 10^{-7})[/tex]

[tex]pH=6.78[/tex]

The pH of pure water is, 6.78

(c) In this, first we have to calculate the pOH when the concentration of hydroxide ion is, 0.10 M.

[tex]pOH=-\log [OH^-][/tex]

[tex]pOH=-\log (0.10)[/tex]

[tex]pOH=1[/tex]

Now we have to calculate the pH.

[tex]pH+pOH=14\\\\pH=14-pOH\\\\pH=14-1=13[/tex]

The pH of solution is, 13

At 40.8°C, the [H+] and [OH-] concentrations in pure water are both 1.71 × 10^−7 M. The pH of pure water at 40.8°C is 6.77. If the [OH-] concentration in a solution is 0.10 M, the pH at 40.8°C is 13.00.

At 40.8°C, the value of Kw is given as 2.92 × 10^−14.

a. To calculate the [H+] and [OH-] concentrations in pure water at 40.8°C, we can use the fact that [H+] × [OH-] = Kw. Since water is neutral, the concentrations of [H+] and [OH-] are equal.

Using the given value of Kw, we have:

[H+] × [H+] = 2.92 × 10^−14

Solving for [H+], we find that [H+] = [OH-] = 1.71 × 10^−7 M.

b. The pH of pure water at 40.8°C can be calculated using the formula pH = -log[H+]. Substituting the value of [H+], we find that the pH is equal to 6.77.

c. If the hydroxide ion concentration in a solution is 0.10 M, we can calculate the pH using the formula pH = 14 - pOH. Since the [OH-] concentration is given as 0.10 M, the pOH can be calculated as -log(0.10) = 1.00. Substituting this value into the pH formula, we find that the pH is equal to 13.00.

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Answer:

The equation that represents how the energy of an electromagnetic wave is related to the frequency of the wave and to the wavelength of the wave is known as the Planck - Einstein equation.

Such equation states that the energy of a photon of light (electromagnetic radiation) is proportional to its frequency:

Where:

Since the frequency and the wavelength are inversely related as per the equation λ = c / f, where λ is the wavelength and c is the speed of light, you can derive the equation that relates the energy of an electromagnetic wave with the wavelength:

Where  λ is the wavelength and c is the speed of light.

The value of c in vacuum is a constant and is equal to 299,792,458 m/s m/s, which is usually approximated to 3.0 × 10⁸ m/s

*view screenshot for equations*

Answer:

Person one has conduction, person 2 has radiation, and person 3 has convention.

Explanation:

Person 1 is touching the mug to get warm, which is a transfer of heat.

Person 2 is exposed to the fire, which is radiation.

Person 3 is exposed to the warm air of convection.

Explanation:

A process that involves transfer of heat from a hot substance to a cold substance by coming in contact with each other is known as conduction.

For example, a person has his hands cupped around a ceramic mug of hot chocolate then heat is transferring from ceramic mug to the hands.

Whereas a process in which heat energy is transferred in a wave-like motion through the space is known as radiation.

For example, a person is toasting a marshmallow above the fire is getting heat energy in the form of radiation.

Also, third person who is roasting a hot dog above the glowing coals is getting heat energy in the form of radiation.

Hence, we can conclude that primary source of heat transfer for person 1 is conduction, and for both person 2 and 3 is radiation.

Answer:

The order of reaction is 2.

Rate constant is 0.0328 (M s)⁻¹

Explanation:

The rate of a reaction is inversely proportional to the time taken for the reaction.

As we are decreasing the concentration of the reactant the half life is increasing.

a) For zero order reaction: the half life is directly proportional to initial concentration of reactant

b) for first order reaction: the half life is independent of the initial concentration.

c) higher order reaction: The relation between half life and rate of reaction is:

Rate = [tex]\frac{1}{k[A_{0}]^{(n-1)}}[/tex]

Half life =[tex]K\frac{1}{[A_{0}]^{(n-1)} }[/tex]

[tex]\frac{(halflife_{1})}{(halflife_{2})}=\frac{[A_{2}]^{(n-1)}}{[A_{1}]^{(n-1)} }[/tex]

where n = order of reaction

Putting values

[tex]\frac{109}{231}=\frac{[0.132]^{(n-1)}}{[0.280]^{(n-1)}}[/tex]

[tex]0.472=(0.472)^{(n-1)}[/tex]

Hence n = 2

[tex]halflife=\frac{1}{k[A_{0}]}[/tex]

Putting values

[tex]231=\frac{1}{K(0.132)}[/tex]

K = 0.0328

The reaction order is 2 (option B), which is determined by observing the change in half-life with concentration. The rate constant for this second order reaction, calculated using the provided formula, is approximately 0.032 M^-1s^-1.

The reaction order refers to how the rate of a chemical reaction is affected by the concentration of its reactants. When we see that the half-life of the reaction changes as the concentration of the reactant changes, this signifies that the order of the reaction is not zero. In zero order reactions, the half-life is dependent on the initial concentration of reactants. In this case, we see that the half-life of the reaction increases as the concentration decreases, which is characteristic of a second order reaction. Therefore, the answer to the first part is (B) 2.

For a second order reaction, the rate constant can be calculated using the formula t1/2 = 1 / [A]0k rearranging gives k = 1 / [A]0t1/2. Substituting for t1/2 = 109 s, and [A]0 = 0.280M, we get k = 1 / (0.280M * 109 s) which is approximately 0.032 M-1s-1. The units for the rate constant k for a second order reaction are M-1s-1.

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Answer:

a. 392

Explanation:

According to Boyles law, the pressure of a fixed mass of a gas at constant temperature is inversely proportional to the volume.

P1V1=P2V2

P1=488mm Hg

P2=757.8mm Hg

V1=609 mL

Therefore we use the values above in the formula and get:

488 mm Hg×609 mL=757.8 mm Hg×V2

V2=(488mmHg×609 mL)/757.8 mm Hg

=392.177 mL

Answer : The molarity and molality of the solution is, 18.29 mole/L and 499.59 mole/Kg respectively.

Solution : Given,

Density of solution = [tex]1.83g/cm^3=1.83g/ml[/tex]

Molar mass of sulfuric acid (solute) = 98.079 g/mole

98.0 % sulfuric acid by mass means that 98.0 gram of sulfuric acid is present in 100 g of solution.

Mass of sulfuric acid (solute) = 98.0 g

Mass of solution = 100 g

Mass of solvent = Mass of solution - Mass of solute = 100 - 98.0 = 2 g

First we have to calculate the volume of solution.

[tex]\text{Volume of solution}=\frac{\text{Mass of solution}}{\text{Density of solution}}=\frac{100g}{1.83g/ml}=54.64ml[/tex]

Now we have to calculate the molarity of solution.

[tex]Molarity=\frac{\text{Mass of solute}\times 1000}{\text{Molar mass of solute}\times \text{volume of solution}}=\frac{98.0g\times 1000}{98.079g/mole\times 54.64ml}=18.29mole/L[/tex]

Now we have to calculate the molality of the solution.

[tex]Molality=\frac{\text{Mass of solute}\times 1000}{\text{Molar mass of solute}\times \text{Mass of solvent}}=\frac{98.0g\times 1000}{98.079g/mole\times 2g}=499.59mole/Kg[/tex]

Therefore, the molarity and molality of the solution is, 18.29 mole/L and 499.59 mole/Kg respectively.

The molality of concentrated sulfuric acid is [tex]\( 0.500 \, \text{mol/kg} \)[/tex], and the molarity is [tex]\( 0.0183 \, \text{mol/L} \)[/tex].

1. Mass of sulfuric acid [tex](\( \text{H}_2\text{SO}_4 \))[/tex] in 100 g of solution:

[tex]\[ \text{Mass of } \text{H}_2\text{SO}_4 = 98.0 \% \times 100 \, \text{g} = 98.0 \, \text{g} \][/tex]

2. Moles of sulfuric acid [tex](\( \text{H}_2\text{SO}_4 \))[/tex]:

[tex]\[ \text{Moles of } \text{H}_2\text{SO}_4 = \frac{98.0 \, \text{g}}{98.086 \, \text{g/mol}} \approx 1.000 \, \text{mol} \][/tex]

3. Molality [tex](\( m \))[/tex]:

[tex]\[ \text{Molality} = \frac{1.000 \, \text{mol}}{2.0 \, \text{kg}} = 0.500 \, \text{mol/kg} \][/tex]

4. Molarity [tex](\( M \))[/tex]:

[tex]\[ \text{Volume of solution} = \frac{100 \, \text{g}}{1.83 \times 10^{-3} \, \text{kg/cm}^3} \approx 54.6 \, \text{L} \]\[ \text{Molarity} = \frac{1.000 \, \text{mol}}{54.6 \, \text{L}} \approx 0.0183 \, \text{mol/L} \][/tex]

So, the molality of concentrated sulfuric acid is [tex]\( 0.500 \, \text{mol/kg} \)[/tex], and the molarity is [tex]\( 0.0183 \, \text{mol/L} \)[/tex].

Answer:

Explanation:

1) Reactants:

The reactants are:

2) Stoichiometric coefficients:

        Cl₂ (g) + 3F₂ (g) →

3) Product:

       Cl₂ (g) + 3F₂ (g) → 2Cl F₃ (g)

        As you see, that last equation si balanced: 2 atoms of Cl and 6 atoms of F on each side, and you conclude that the formula of the product is ClF₃.

Answer:

Final temperature = 48.6867 °C

Explanation:

The expression for the heat of combustion in bomb calorimeter is:

ΔH = -C ΔT

where,

ΔH is the enthalpy of the reaction

C is the heat capacity of the bomb calorimeter

ΔT is the temperature change

Given in the question:

ΔH°rxn = -1.28 x 10⁴ kJ

From the balanced reaction, 4 moles of aniline reacting with oxygen. Thus, enthalpy change of the reaction in kJ/mol is:

ΔH = -12800 kJ/4 = -3200kJ/mole

Given:

Mass of aniline combusted = 6.55 g

Molar mass of aniline = 93.13 g/mol

Thus moles of aniline = 6.55 / 93.13 moles = 0.0703 moles

The total heat released from 0.0703 moles of aniline is

ΔH = -3200kJ/mole x 0.0703 moles = -224.96 kJ

Given: Heat capacity of calorimeter is 14.25 kJ/°C

T₁ (initial) = 32.9°C

T₂ (final) = ?

From the above formula:

-224.96 kJ = -14.25kJ/°C (T₂ - 32.9)

Solving for T₂ , we get:

T₂ = 48.6867 °C

Answer:

With thermodynamics, one cannot determine the speed of a reaction.

Explanation:

Chemical thermodynamics, a branch of chemistry that deals with study of  interrelation of the heat and the work with the chemical reactions or with the physical changes of the state within confines of laws of thermodynamics.

Chemical thermodynamics' structure is derived from first two laws of chemical thermodynamics. From fundamental equations of Gibbs, a multitude of some equations which relates thermodynamic properties of thermodynamic system can be derived and can be used to calculate the reaction spontaneity, equilibrium constant, etc.

Thermodynamics predicts about the direction, feasibility and the extent of a chemical process, it does not tell anything about the rate at which a chemical process may proceed.

Answer : The value of [tex]\Delta E[/tex] of the reaction is, -553.8 KJ

Explanation :

Formula used :

[tex]\Delta E=\Delta H-\Delta n_g\times RT[/tex]

where,

[tex]\Delta E[/tex] = internal energy of the reaction = ?

[tex]\Delta H[/tex] = enthalpy of the reaction = -184.6 KJ/mole = -184600 J/mole

The balanced chemical reaction is,

[tex]H_2(g)+Cl_2(g)\rightarrow 2HCl(g)[/tex]

when the moles of [tex]H_2\text{ and }Cl_2[/tex] are 3 moles then the reaction will be,

[tex]3H_2(g)+3Cl_2(g)\rightarrow 6HCl(g)[/tex]

From the given balanced chemical reaction we conclude that,

[tex]\Delta n_g[/tex] = change in the moles of the reaction = Moles of product - Moles of reactant = 6 - 6 = 0 mole

R = gas constant = 8.314 J/mole.K

T = temperature = [tex]25^oC=273+25=298K[/tex]

Now put all the given values in the above formula, we get:

[tex]\Delta E=(-184600J/mole\times 3mole)-(0mole\times 8.314J/mole.K\times 298K)[/tex]

[tex]\Delta E=-553800J[/tex]

[tex]\Delta E=-553.8KJ[/tex]

Therefore, the value of [tex]\Delta E[/tex] of the reaction is, -553.8 KJ

The reaction H2(g) + Cl2(g) → 2HCl(g) is exothermic with a standard enthalpy change of -184.6 kJ/mol. For 3 moles each of H2 and Cl2, the energy released (ΔU) is -276.9 kJ. At 1 atm and 25°C, ΔH and ΔU are nearly the same due to insignificant work against atmospheric pressure.

The given reaction (H2(g) + Cl2(g) → 2HCl(g)) is an exothermic reaction with a standard enthalpy change (ΔH) of -184.6 kJ/mol. This means that this amount of energy is released for every 1 mole of H2 and 1 mole of Cl2 that react to form 2 moles of HCl. If we're considering 3 moles of H2 and 3 moles Cl2, we are effectively dealing with 1.5 times the standard reaction. Hence, the total energy released (ΔU) is -184.6 kJ/mol * 1.5 = -276.9 kJ. An important note is that ΔH and ΔU are approximately the same for reactions at constant pressure and low temperatures (like 1 atm and 25°C), due to minimal work done against atmospheric pressure.

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Answer:

B

Explanation:

It has 2 NH4 molecules and 1 CO3 molecule.

NH4 has a molar mass of 18g/mol. Since there are two NH4s, it makes up 36g of the (NH4)2CO3.

CO3 has a molar mass of 60g/mol. Since there is one CO3, it makes up 60g of the (NH4)2CO3.

If you add up 36 and 60, you will get 96g.

Answer:

17 protons and 20 neutrons

Explanation:

Chlorine (Cl) is an element of the periodic table whose atomic number is 17 and enters the group of halogens.

Cl37 is a stable isotope (atom from an element with the same atomic number but different atomic mass) of chlorine.

Is an isotope of chlorine found in nature, representing ~24% of the total.

Answer:

M of Ba(OH)₂ = 0.818 M.

Explanation:

Ba(OH)₂ + 2HNO₃ → Ba(NO₃)₂ + 2H₂O,

It is clear that every 1.0 mol of Ba(OH)₂ needs 2 mol of HNO₃ to be neutralized completely.

∴ (nMV) of Ba(OH)₂ = (nMV) for HNO₃.

where, n is the no. of producible H⁺ or OH⁻ of the acid or base, respectively.

M is the molarity of the acid or base.

V is the volume of the acid or base.

For Ba(OH)₂:

n = 2, M = ??? M, V = 20.0 mL.

For HNO₃:

n = 1, M = 0.85 M, V = 38.5 mL.

∴ M of Ba(OH)₂ = (nMV) of HNO₃ / (MV) for Ba(OH)₂ = (1)(0.85 M)(38.5 L)/(2)(20.0 mL) = 0.818 M.

Answer:

132 g/mol

Explanation:

(NH₄)₂SO₄ has 2 nitrogen atoms, 8 hydrogen atoms, 1 sulfur atom, and 4 oxygen atoms.

From the periodic table, the molar mass of each element is:

N: 14.0 g/mol

H: 1.01 g/mol

S: 32.1 g/mol

O: 16.0 g/mol

So the molar mass of the compound is:

2N × (14.0 g/mol N) + 8H × (1.01 g/mol H) + 1S × (32.1 g/mol S) + 4O × (16.0 g/mol O)

= 28.0 + 8.08 + 32.1 + 64.0 g/mol

= 132 g/mol

If you need more precision, use more significant figures for the element molar masses.

The combustion reaction of methanol gaseous:

[tex]2CH_3OH(g) +3O_2(g) \longrightarrow 2CO_2(g) +4H_2O (g)[/tex]

A combustion reaction can be defined as a reaction that gives fire and takes place at an elevated temperature. A combustion reaction is an exothermic, redox reaction that commonly occurs between a hydrocarbon and mostly oxygen gas in the atmosphere.

Oxygen is the essential ingredient for the combustion reaction because combustion cannot happen without oxygen. An example of combustion is the burning of wood or solid fuels. The carbon in wood or coal reacts with oxygen gas in the air to liberate heat and gaseous products.

Combustion Reactions such as during the combustion of methanol react with molecules of oxygen gas to give carbon dioxide and water. The balanced chemical equation of the combustion reaction of methanol and oxygen is as follows:

[tex]2CH_3OH(g) +3O_2(g) \longrightarrow 2CO_2(g) +4H_2O (g)[/tex]

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Answer:

ΔG° =-990.17 kJ /mol

Explanation:

The equation is:

ΔG° = Δ H° -TΔS°  ....................equation 1

Δ H°rxn = Δ H°f (products)- Δ H°f(reactants)

Δ H°rxn = [[2XΔ H°f(SO₂)]+[2Δ H°f(H₂O)]-[2Δ H°f(H₂S)]+[3Δ H°f(O₂)]

Δ H°rxn = [2X(-296.8)+2(-241.8)]-[2X(-20.6)] = -1036

Δ S°rxn = Δ S°f (products)- Δ S°f(reactants)

Δ S°rxn = [[2XΔ S°f(SO₂)]+[2Δ S°f(H₂O)]-[2Δ S°f(H₂S)]+[3Δ S°f(O₂)]

Δ S°rxn = [2(248.2)+2(188.8)]-[2(205.8)+3(205.2)] = -153.8 J/mol K

      = -0.1538 KJ /mol

Putting values in equation 1  ( T = 298 K)

ΔG° = Δ H° -TΔS° = (-1036)-[(298)(-0.1538)

ΔG° =-990.17 kJ /mol

To calculate the standard change in free energy, ΔG°rxn, use the equation: ΔG°rxn = ΔH°rxn - TΔS°rxn. Calculate ΔH°rxn using the enthalpy of formation values and ΔS°rxn using the entropy values. Substitute the calculated values into the equation to find ΔG°rxn.

To calculate the standard change in free energy, ΔG°rxn, we can use the equation: ΔG°rxn = ΔH°rxn - TΔS°rxn. From the given information, we can calculate the values for ΔH°rxn and ΔS°rxn. First, calculate ΔH°rxn by using the enthalpy of formation values: ΔH°rxn = (2 mol × ΔHf° SO2(g) + 2 mol × ΔHf° H2O(g)) - (2 mol × ΔHf° H2S(g) + 3 mol × ΔHf° O2(g)). Then, calculate ΔS°rxn by using the entropy values: ΔS°rxn = (2 mol × S° SO2(g) + 2 mol × S° H2O(g)) - (2 mol × S° H2S(g) + 3 mol × S° O2(g)). Finally, with the calculated values, substitute them into the equation to find the value for ΔG°rxn.

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Answer:

A. Nuclear energy

Explanation:

Nuclear energy is the energy created when light atoms combine in a fusion reaction or when heavier atoms split in a fission reaction.

Option C. Na+ has the inert gas structure of argon is false. Sodium has 11 protons and 11 electrons. When it loses an electron and forms Na+, it has 11 protons and 10 electrons. The inert gas that has 10 electrons is Neon not Argon. Argon has 18 electrons.

Further Explanation:

A. Na+ electron configuration is like the stable inert gas configuration - TRUE

Na has an electron configuration of 2,8,1 (or [tex]1s^2 \ 2s^2 \ 2p^6 \ 3s^1[/tex]). When it loses its valence electron, its electron configuration becomes 2,8 (or [tex]1s^2 \ 2s^2 \ 2p^6 [/tex]). This is similar to the electron configuration of Neon which has a full valence shell. A full valence shell has 8 electrons.

B. To remove the second electron, the increased attraction of protons to electrons must be overcome - TRUE

Ionization energy is the amount of energy needed to remove a valence electron from a gaseous atom. This energy is required to overcome the attraction of the valence electron to the nucleus. The closer the orbital (i.e. the electron), the stronger the attraction of the electrons to the nucleus. Hence, removing a second electron, which is now closer to the nucleus than the first, will require more energy to overcome its stronger attraction to the protons in the nucleus.

C. Na+ has the inert gas structure of Argon - FALSE

The electron structure of Na+ is 2,8 (or [tex]1s^2 \ 2s^2 \ 2p^6 [/tex] ).

The electron structure of Ar is 2,8,8 ( or [tex]1s^2 \  2s^2 \ 2p^6 \ 3s^2 \ 3p^6[/tex]).

D. Both A and C are False - FALSE

Only C is false.

E. Items A, B, and C are False - FALSE

A and B are true. Only C is false.

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Keywords: ionization energy, electron configuration

Answer : The heat released per gram of the compound reacted with oxygen is, 71.915 kJ

Solution :

The balanced chemical reaction is,

[tex]2B_5H_9(l)+12O_2(g)\rightarrow 5B_2O_3(s)+9H_2O(l)[/tex]

The expression for enthalpy change is,

[tex]\Delta H=\sum [n\times \Delta H_f(product)]-\sum [n\times \Delta H_f(reactant)][/tex]

[tex]\Delta H=[(n_{H_2O}\times \Delta H_{H_2O})+(n_{B_2O_3}\times \Delta H_{B_2O_3})]-[(n_{B_5H_9}\times \Delta H_{B_5H_9})+(n_{O_2}\times \Delta H_{O_2})][/tex]

where,

n = number of moles

Now put all the given values in this expression, we get

[tex]\Delta H=[(9\times -285.83)+(5\times -1271.94)]-[(2\times 73.2)+(12\times 0)]\\\\\Delta H=-9078.57kJ[/tex]

Now we have to calculate the heat released per gram of the compound reacted with oxygen.

As we know that,

1 mole of [tex]B_5H_9[/tex] has 63.12 grams of mass

So, 2 mole of [tex]B_5H_9[/tex] has [tex]2\times 63.12=126.24[/tex] grams of mass

As, 126.24 g of [tex]B_5H_9[/tex] release heat = 9078.57 kJ

So, 1 g of [tex]B_5H_9[/tex] release heat = [tex]\frac{9078.57}{126.24}=71.915kJ[/tex]

Therefore, the heat released per gram of the compound reacted with oxygen is, 71.915 kJ

The heat released per gram of the compound reacted with oxygen is -71.92 KJ/mol per gram of B5H9 reacted.

The equation goes as follows;

2B5H9(l) + 12O2(g) → 5B2O3(s) + 9H2O(l)

We have the following information;

ΔH°f  B5H9(l) =  73.2 kJ/mol

ΔH°f  B2O3(s) = −1271.94 kJ/mol

ΔH°f  H2O(l) = −285.83 kJ/mol

Note that;

ΔHrxn = ∑ΔH°f (products) - ΔH°f (reactants)

ΔHrxn =  ∑(5 × ( −1271.94 kJ/mol)) + (9 × ( −285.83 kJ/mol)) - ∑(2 × (73.2 kJ/mol) + (12 × 0)

ΔHrxn = -9078.57  kJ/mol

Since 1 mole of B5H9 = 63.12 g/mol

Two moles of B5H9 reacted so 2 moles × 63.12 g/mol = 126.24 g

Heat released per gram of B5H9 reacted = -9078.57  kJ/mol/126.24 g

= -71.92 KJ/mol per gram of B5H9 reacted.

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Answer : The percent by mass of NaCl and KCl are, 18.11 % and 81.88 % respectively.

Explanation :

As we know that when a mixture of NaCl and KCl react with excess [tex]AgNO_3[/tex] then the silver ion react with the chloride ion in both NaCl and KCl to form silver chloride.

Let the mass of NaCl be, 'x' grams and the mass of KCl will be, (0.9440 - x) grams.

The molar mass of NaCl and KCl are, 58.5 and 74.5 g/mole respectively.

First we have to calculate the moles of NaCl and KCl.

[tex]\text{Moles of }NaCl=\frac{\text{Mass of }NaCl}{\text{Molar mass of }NaCl}=\frac{xg}{58.5g/mole}=\frac{x}{58.5}moles[/tex]

[tex]\text{Moles of }KCl=\frac{\text{Mass of }KCl}{\text{Molar mass of }KCl}=\frac{(0.9440-x)g}{74.5g/mole}=\frac{(0.9440-x)}{74.5}moles[/tex]

As, each mole of NaCl and KCl gives one mole of chloride ions.

So, moles of chloride ions in NaCl = [tex]\frac{x}{58.5}moles[/tex]

Moles of chloride ions in KCl = [tex]\frac{(0.9440-x)}{74.5}moles[/tex]

The total moles of chloride ions = [tex]\frac{x}{58.5}moles+\frac{(0.9440-x)}{74.5}moles[/tex]

Now we have to calculate the moles of AgCl.

As we know that, this amount of chloride ion is same as the amount chloride ion present in the AgCl precipitate. That means,

Moles of AgCl = Moles of chloride ion = [tex]\frac{x}{58.5}moles+\frac{(0.9440-x)}{74.5}moles[/tex]

Now we have to calculate the moles of AgCl.

The molar mass of AgCl = 143.32 g/mole

[tex]\text{Moles of }AgCl=\frac{\text{Mass of }AgCl}{\text{Molar mass of }AgCl}=\frac{1.903g}{143.32g/mole}=0.0133moles[/tex]

Now we have to determine the value of 'x'.

Moles of AgCl = [tex]\frac{x}{58.5}moles+\frac{(0.9440-x)}{74.5}moles[/tex]

0.0133 mole = [tex]\frac{x}{58.5}moles+\frac{(0.9440-x)}{74.5}moles[/tex]

By solving the term, we get the value of 'x'.

[tex]x=0.171g[/tex]

The mass of NaCl = x = 0.171 g

The mass of KCl = (0.9440 - x) = 0.9440 - 0.171 = 0.773 g

Now we have to calculate the mass percent of NaCl and KCl.

[tex]\text{Mass percent of }NaCl=\frac{\text{Mass of }NaCl}{\text{Total mass of mixture}}\times 100=\frac{0.171g}{0.9440g}\times 100=18.11\%[/tex]

[tex]\text{Mass percent of }KCl=\frac{\text{Mass of }KCl}{\text{Total mass of mixture}}\times 100=\frac{0.773g}{0.9440g}\times 100=81.88\%[/tex]

Therefore, the percent by mass of NaCl and KCl are, 18.11 % and 81.88 % respectively.