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Question 1

What is the equilibrium expression for:

2HI(g) ↔ H2(g) + I2(g)?

Select one: Explanation

Keq= [Gas Products]/ [Gas Reactants]

Keq= [H2][I2]/[HI]^2

Question 2

Which of the following show correct proportions for the above reaction?

(For d and e, x is a variable. For example, x could equal 0.3, or 2, etc.)

Select one or more:    Explanation

HI:H2:I2

2:1:1

any variable of that

Question 3

For the reaction in the previous problem, that is,

2HI(g) ↔ H2(g) + I2(g) Keq = 0.016

Initially a container contains 0.33 M HI and no product. What is the equilibrium concentration of H2? Explanation

Hint, in solving the equation you could use the quadratic equation, but in this case, it is easier to take the square root of both side and solve the simple algebraic equation.

2HI <--> H2+I2

I  0.3M  0M  0M

C- 2x  +x  +x

E 0.3-2x x  x

keq = 0.016= x(x)/(0.33-2x)^2

sqrt (0.016)= x/(0.33-2x)

0.12649(0.33-2x)=x

0.041742-0.25298x=x

0.041742=1.25298x

x = 0.033

Question 4

For the reaction:

2HBr(g) ↔ H2(g) + Br2(g)

Initially a container contains 0.64 M HBr and no product. What is the equilibrium concentration of HBr if the equilibrium concentration of H2 is 0.20 M? (Hint provided in feedback.) Explanation

Hint--how much HBr is needed to produce the H2? Subtract this amount from the original amount to find out how much is left.

2HBr(g) ↔ H2(g) + Br2(g)
I  0.64M        0M       0M
C -2x             +x        +x
E 0.24          0.2        0.2

x=0.2
0.64-2(0.2)= 0.24

Question 5

For the reaction:

2HBr(g) ↔ H2(g) + Br2(g)

0.45 M Br2 is at equilibrium with a certain concentration of HBr and H2. The concentration of bromine is increase by 0.2 M and the system establishes a new equilibrium. Which of the following statements are true?
All answers must be correct to get credit.

Concentration and Le Chatelier's Principle

Select one or more:   Explanation

2HBr(g) ↔ H2(g) + Br2(g)

I

C

x                  y            0.45M

2HBr(g) ↔ H2(g) + Br2(g)

I     x              y                 0.65

C    +2a         -a                  -a

E  x+2a        y-a               0.65-a

HBr increases

Br2 decreases

H2 decreases

Question 6

For the reaction:

N2(g) + 3H2(g) ↔ 2NH3(g)

Nitrogen, hydrogen, and ammonia are at equilibrium at 10 atm. The pressure is increased to 50 atm by decreasing the volume. The system moves to establishes a new equilibrium. Which of the following statements are true?

Pressure and Le Chatelier's Principle

Select one or more:    Explanation

N2(g) + 3H2(g) ↔ 2NH3(g)

10 atm = equilibrium

P increased by V decreasing (P=nRT/V) --> inversely proportional

When P increases/V decreases equilibrium prefers the side with the least amount of moles of gas

....on the left there are 4 moles of gas and on the right there are 2

so it will go to the right

meaning that the moles of NH3 will increase and moles of N2 and H2 will decrease

Question 7

For the reaction:

N2(g) + 3H2(g) ↔ 2NH3(g)

Nitrogen, hydrogen, and ammonia are at equilibrium at 10 atm. The pressure is dropped to 2 atm by increasing the volume. The system moves to establishes a new equilibrium. Which of the following statements are true?

Select one or more:    Explanation

N2(g) + 3H2(g) ↔ 2NH3(g)

When pressure decreases it favors the side with the most moles of gas

So it will go the left  meaning that N2 and H2 will increase whilst NH3 will decreases

Question 8

For the reaction:

2HBr(g) ↔ H2(g) + Br2(g)

Hydrogen bromide, hydrogen, and bromine are at equilibrium at 8 atm. The pressure is decreased to 3 atm by increasing the volume. The system moves to establishes a new equilibrium. Which of the following statements are true?

Select one or more:    Explanation

2HBr(g) ↔ H2(g) + Br2(g)

By decreasing the pressure and increasing the volume the reaction would favor the side with most moles of gas, but in this case they have equal cases of gaseous moles so the reaction will stay in equilibrium.

Meaning that nothing will change!!!

Question 9

For the reaction:

CaCO3(s) ↔ CaO(s) + CO2(g)       Kp= 1.16 at 800o

The system is at equilibrium. There are 2 mol of CaCO3, 6 mol CaO, and the CO2 pressure is 1.16 atm at 800oC. Which of the following produces more CO2 at the new equilibrium?

Select one or more: Explanation

CaCO3(s) ↔ CaO(s) + CO2(g)       Kp= 1.16 at 800o

I

C

E 2                       6        1.16

In order to produce more CO2 the only possibility is to decrease pressure as on the left there is only a solid which plays no role in the equilibrium.

Question 10

For the reaction:

N2(g) + 3H2(g) ↔ 2NH3(g) ΔH = -92 kJ

Which of the following statements are true?

Select one or more:  Explanation

N2(g) + 3H2(g) ↔ 2NH3(g) ΔH = -92 kJ

ΔH = -92 kJ   === exothermic

meaning that heat is a product

so in order to increase ammonia concentration the temperature must decrease

Question 11

Pick the correct statements for the reaction given below. (To the right means the new equilibrium has more product, to the left means the new equilibrium has more reactant.)

Si(CH3)4 (g)  +  12CO2(g)   <--> SiO2(s)  + 16CO(g)

Select one or more:   Explanation

YOU GOT THIS KIDDOS

increasing the GAS products moves the equilibrium to the reactants and vice versa

decreasing the GAS products moves the equilibrium to the products and the same goes for the reactants

Question 12

Pick the correct statements for the above reaction.

Select one or more:  Explanation

All must be correct to get full credit. Remember that changing the amount of pure liquids and solids has no effect (as long as some remains).

H20 is a liquid so genuinely has no effect on anything-also it isn't even in the en above

And by expanding the volume aka decreasing the pressure it will go to the right because there 16 moles of gas in comparison to the 12 moles of gas on the right

Question 13

Pick the correct statements for the above reaction.

Select one or more:  Explanation

Hint--an inert gas is not part of the equilibrium expression and has no effect on the equilibrium concentrations

By increasing the pressure, the equilibrium will go to the left were there are only 12 moles of gas in comparison to 16 on the right

Question 14

For the reaction:

2HI(g) ↔ H2(g) + I2(g) Keq = 0.016

Initially a container contains 0.60 M HI, 0.038 M H2, and 0.15 M I2 at equilibrium. What is the new equilibrium concentration of H2, if the H2concentration is increased by 0.190 M?

New Equilibrium Concentration Explanation

2HI(g) ↔ H2(g) + I2(g) Keq = 0.016

I 0.6        0.228        0.15

C +2x        -x            -x

E 0.6+2x  0.228-x  0.15-x

keq = 0.016 = [H2][I2]/[HI]^2

0.016= (0.228-x)(0.15-x)/(0.6+2x)^2

0.016= 0.0342-0.378x+x^2/(0.36+2.4x+4x^2)

0.0576 + 0.0384x + 0.064x^2= 0.0342 - 0.378x +x^2

-0.936x^2+ 0.4164x-0.02844=0

x= -0.4164(+/-) sqrt(0.17339-4(-0.936)(-0.02844))/(2*-0.936)

x= -0.4164 (+/-) sqrt(0.0669)/(2* -0.936)

x= 0.084258

0.228- (0.084258)=0.1437