COOP IV ________________________

Chem 1403-40 (name)

Dr. Robert E. Belford

 

 

1. Does the following reaction favor reactants or products?

2SO3(g) --> 2SO2(g) + O2(g) K = 7.9 x 10-9

 

Reactants, K is a very small fraction

 

 

2. Calculate the equilibrium constant Kc for the reaction

PCl3(g) + Cl2(g) --> PCl5(g)

when a mixtures of the gasses has the following equilibrium concentrations

 

[PCl3] = 2.4 x 10-2, [Cl2] = 8.9 x 10-2, [PCl5] = 3.7 x 10-2

 

 

 

 

 

3. Using the results from question 2, determine Kc for the following reaction.

 

PCl5(g) --> PCl3(g) + Cl2(g)

 

 

 

 

4. Using the results from question 2, determine Kp for the following reaction at 25 deg C.

PCl3(g) + Cl2(g) --> PCl5(g)

 

 

 

 

 

 

 

 

 

 

5. Consider the following equilibrium:

2HI(g) <==> H2(g) + I2(g)

 

At equilibrium a 5.00 L vessel contains 4.50 mol I2, 4.50 mol H2 and an unknown amount of HI. Kc for this equilibrium is 0.0183. What is the equilibrium concentration of HI?

 

 

 

 

 

 

6. For the reaction H2(g) + I2(g) --> 2HI(g), DHo = -9.4kJ, for each of the following changes, will the equilibrium product concentration increase or decrease?

 

a. Addition of hydrogen Increase

b. Removal of Iodine Decrease

c. Increase in Pressure No Effect

d. An increase in Temperature Decrease

 

 

 

7. For the reaction 2NF3 (g) N2(g) + 3F2(g) , DHo = +4.3kJ/mol, for each of the following changes, will the equilibrium product concentration increase or decrease?

 

a. Addition of Fluorine Decrease

b. Removal of Nitrogen Increase

c. Increase in Pressure Decrease

d. An increase in Temperature Increase

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

8. Consider the reaction

 

2SiO(g) <==> 2Si(l) + O2(g); Kc = 9.62 x 10-1

 

If 1.00 mol SiO is placed into a 1.00 L container, what are the equilibrium concentrations of all species?

 

 

2SiO(g) <==> 2Si(l) + O2(g)

Initial moles: 1 0 0

Change: -2x +x +x

Equil. Conc. [1-2x] (constant) [x]

 

 

The first answer is nonsense, so [O2] = 0.247M & SiO=0.506M

 

 

9. Calculate the value of the equilbrium constant for the reaction

 

2NO(g) + O2(g) <==> N2O4(g) K = ?

 

Knowing the following equilibrium constants at the same Temperature and Pressure

 

2NO(g) + O2(g) <==> NO2(g) K1 = 2.0 x 102

 

N2O4(g) <==> 2 NO2(g) K2 = 7.2 x 10-4

 

Writing the second one backward makes it the reciprocal of the forward, then adding coupled equations makes the coupled equilibrium constant multiplicative

 

 

 

 

 

 

 

 

10. A mixture of 0.659 g of H2 and 26.7 g Br2 is heated in a 3 L container. These substances react as follows

H2(g) + Br2(g) <==> 2HBr(g)

At equilibrium the vessel is found to contain 10.4 g of Br2. Calculate Kc for this reaction

 

 

 

 

H2(g) + Br2(g) <==> 2HBr(g)

[Initial]: .110 0.0557 0

Change: -x -x 2x

[Equilibrium]: .11-x .0557-x 2x

[0.0217]

From Bromine data: 0.0217 = 0.0557-x => x = 0.036

So [H2]eq = 0.11 0.026 = 0.084 and [HBr]eq = 2(0.036) = 0.072

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

11. Given the reaction:

Cl2(g) + 2HBr(g) Br2(g) + 2HCl(g)

70.9g of chlorine is mixed with 161.8g of HBr in a 10.0 L vessel. What are the equilibrium concentrations of all species if Kc = 1.5 x 101?

The initial molarity of chlorine is 70.9g(70.9g/mol)/10L=0.100M

The initial molarity of hydrogen bromide is 161.8g(80.9g/mol)/10L=0.200M

 

Cl2(g) + 2HBr(g) Br2(g) <==> 2HCl(g)

Initial moles: .1 .2 0 0

Change: -x -2x +x +2x

Equil. Conc. [.1-x] [.2-2x] [x] [2x]

 

 

[Cl2]= .1-.0712 = 0.0288M

[HBr] = .2-2(0.0712) = 0.0576M

[Br2]=.0712

[HCl] = 2(0.0712) = 0.142M

 

12. Calculate the equilibrium constant if one mole of pure ethyl alcohol is mixed with one mole of pure acetic acid at room temperature. The products are ethyl-methyl ester and the equilibrium mixture contains 2/3 moles of the ester.

C2H5OH + CH3OOH H2O + H3CCOOCH2CH3

Initial moles: 1 1 0 0

Change: -x -x +x +x

Equil. moles [1-x] [1-x] [x] [x]

X=2/3, 1-X=1/3

EquilConc: [1/3]/V [1/3]/V [2/3]/V [2/3]/V