Q: A chemist starts with 0.500 mol of HCl(g) in a 250.0 mL vessel. For $$2\mathrm{HCl(g) \rightleftharpoons H_2$(g) + Cl_2$(g)}$$ with $$K = 3.2 \times 10$$^{-34}$$, what is the equilibrium concentration of H_2$(g)?

$$3.6 \times 10$$^{-17}$$ mol/L

Question 1

A patient with type 1 diabetes is at risk for low blood pH due to the accumulation of which compound in the blood, as a result of cellular respiration?

Accepted Answer

Carbonic acid, H2CO3

Question 2

A doctor administers hydrogen carbonate ions, $$\mathrm{$$HCO_3$$^-}$$, to a patient with low blood pH. According to Le Chatelier's principle, what effect does this have on the equilibrium system $$\mathrm{CO_2$(aq) + H_2O(l) \rightleftharpoons H_2CO_3(aq)}$$?

Accepted Answer

The equilibrium shifts to the left, decreasing $$\mathrm{H_2CO_3}$$ concentration.

Question 3

Which of the following statements about the equilibrium constant, $$K$$, is correct?

Accepted Answer

It remains constant unless the temperature changes.

Question 4

Given the reaction $$\mathrm{N_2$(g) + 3H_2(g) ightleftharpoons 2NH_3(g)}$$ with $$K = 6.01 	imes 10$$^{-2}$$ at 500°C, what will happen if Q = 1.25$$ 	imes $$10^7$$ for the initial concentrations?

Accepted Answer

The system will shift to the left, forming more reactants.

Question 5

For the reaction $$\mathrm{2HI(g) \rightleftharpoons H_2$(g) + I_2$(g)} at 445$$°C with $$K = 0.020$$, if $$[HI] = 0.20$$ mol/L, $$[H_2$] = 0.15$$ mol/L, and $$[I_2$] = 0.090$$ mol/L, what is the value of $$Q$$ and in which direction will the reaction shift?

Accepted Answer

$$Q = 0.34$$, shift left

Question 6

A chemist places 0.80 mol/L $$\mathrm{N_2O_4(g)}$$ and 1.55 mol/L $$\mathrm{NO_2$(g)} in a $$vessel at 55°C. For $$\mathrm{N_2O_4(g) \rightleftharpoons 2NO_2(g)}$$ with $$K = 0.87$$, what is $$Q$$ and what will happen?

Accepted Answer

$$Q = 3.0$$, system shifts left

Question 7

For the reaction $$\mathrm{CO(g) + H_2O(g) \rightleftharpoons CO_2$(g) + H_2$(g)}$$ with $$K = 5.10 at 700 K$$, if all initial concentrations are 2.500 mol/L, what is the direction of the shift to reach equilibrium?

Accepted Answer

Shift to the right, forming more products.

Question 8

A student calculates $$x$$ for the equilibrium $$\mathrm{2CO_2(g) ightleftharpoons 2CO(g) + O_2$(g)}$$ with $$K = 6.40 	imes 10$$^{-7}$$ and initial $$[$$CO_2$$] = 0.250$$ mol/L. Why is it reasonable to assume 0.250 - 2x$$ \approx 0.250$$?

Accepted Answer

Because $$K is $$much smaller than the initial concentration, so $$x$$ will be very small.

Question 9

For the reaction $$\mathrm{N_2O_4(g) \rightleftharpoons 2NO_2(g)}$$ with $$K = 4.50$$ and initial $$[N_2O_4] = 0.500$$ mol/L, why can't you assume $$0.500 - x \approx 0.500$$?

Accepted Answer

Because the ratio $$[N_2O_4]_{initial}/K is $$much less than 100, so $$x is $$not negligible.

Question 10

A sealed 1.00 L flask contains 2.00 mol CO and 2.00 mol H$$_2O. At $$equilibrium, 1.30 mol of CO$$_2$$ and 1.30 mol of H$$_2$$ are present. What is the value of $$K$$ for $$\mathrm{CO(g) + H_2O(g) \rightleftharpoons CO_2$(g) + H_2$(g)}$$?

Accepted Answer

$$K = 2.6$$

Question 11

Which of the following best describes the reaction quotient, $$Q$$?

Accepted Answer

The ratio of the concentrations of products to reactants at any point in time.

Question 12

If $$Q \u003c K$$ for a chemical system, what will happen as the system moves toward equilibrium?

Accepted Answer

The reaction will shift to the right, forming more products.

Question 13

A chemist starts with 0.500 mol of HCl(g) in a 250.0 mL vessel. For $$2\mathrm{HCl(g) ightleftharpoons H_2$(g) + Cl_2$(g)}$$ with $$K = 3.2 	imes 10$$^{-34}$$, what is the equilibrium concentration of H_2$(g)?

Accepted Answer

$$3.6 	imes 10$$^{-17}$$ mol/L

Question 14

In a 2.00 L vessel at 440°C, 4.00 mol H$$_2$$ and 1.99 mol I$$_2$$ are combined. At equilibrium, $$[H_2$] = 1.07$$ mol/L for $$\mathrm{H_2$(g) + I_2$(g) \rightleftharpoons 2HI(g)}$$ with $$K = 49.7. $$What is $$[HI] at $$equilibrium?

Accepted Answer

$$1.86$$ mol/L

Question 15

A solution contains $$0.16$$ mol of $$\mathrm{$$HCO_3$$^-} in$$ $$1.00 L. $$For $$\mathrm{$$HCO_3$$^-} ightleftharpoons \mathrm{H^+} + \mathrm{CO_3$^{2-}}$$ with $$K = 5.6 	imes 10$$^{-11}$$, what is the equilibrium concentration of $$\mathrm{$$CO_3$$^{2-}}$$?

Accepted Answer

Lesson 7.5: Quantitative Changes in Chemical Equilibrium Systems (12 Chem)

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