Q: For the dissolution of CaF$$_2 in $$water, $$\text{CaF}_2(s) \rightleftharpoons \text{Ca}^{2+}(aq) + 2 \text{F}^-(aq)$$, what is the expression for $$K_{sp}$$?

$$K_{sp} = [\text{Ca}^{2+}][\text{F}^-]^2$$

Question 1

Which of the following best describes the condition for chemical equilibrium in a reversible reaction?

Accepted Answer

The rates of the forward and reverse reactions are equal.

Question 2

For the reaction $$3 	ext{H}_2(g) + 	ext{N}_2(g) ightleftharpoons 2 	ext{NH}_3(g)$$, what happens to the equilibrium position if the volume of the container is decreased?

Accepted Answer

The reaction shifts toward the products to decrease the number of gas molecules.

Question 3

Given the reaction $$	ext{COCl}_2(g) ightleftharpoons 	ext{CO}(g) + 	ext{Cl}_2(g)$$, if the initial pressure of COCl$$_2 is 1.0 $$atm and the total pressure at equilibrium is 1.2 atm, what is the value of $$K_p$$?

Accepted Answer

$$K_p = \frac{(0.2)(0.2)}{0.8}$$

Question 4

Which of the following statements about equilibrium constants is correct?

Accepted Answer

A large $$K$$ value indicates that products are favored at equilibrium.

Question 5

For the reaction $$	ext{N}_2(g) + 	ext{O}_2(g) ightleftharpoons 2 	ext{NO}(g)$$ with $$K_c = 0.10$$, if the initial concentrations are $$[	ext{N}_2] = 0.200 M$$, $$[	ext{O}_2] = 0.200 M$$, and $$[	ext{NO}] = 0 M$$, what is the direction of the reaction?

Accepted Answer

The reaction will shift to the right, toward products.

Question 6

If the equilibrium constant for a reaction is $$K = 5 	imes 10$$^{-6}$$, which statement is true?

Accepted Answer

The reaction strongly favors the formation of reactants.

Question 7

Which of the following correctly describes the effect of adding more NO$$_2 to $$the equilibrium $$	ext{N}_2	ext{O}_4(g) ightleftharpoons 2 	ext{NO}_2(g)$$?

Accepted Answer

The reaction shifts to the left, producing more N$$_2O$_4.$$

Question 8

For the reaction $$	ext{N}_2(g) + 3 	ext{H}_2(g) ightleftharpoons 2 	ext{NH}_3(g)$$, what happens to the equilibrium constant $$K if $$the temperature is increased for an exothermic reaction?

Accepted Answer

The value of $$K$$ decreases.

Question 9

Which of the following is excluded from equilibrium constant expressions?

Accepted Answer

Pure solids and pure liquids

Question 10

If a chemical equation is reversed, how is the equilibrium constant $$K$$ affected?

Accepted Answer

It is inverted ($$K_{reverse} = 1/K_{forward}).$$

Question 11

For the dissolution of CaF$$_2 in $$water, $$	ext{CaF}_2(s) ightleftharpoons 	ext{Ca}^{2+}(aq) + 2 	ext{F}^-(aq)$$, what is the expression for $$K_{sp}$$?

Accepted Answer

$$K_{sp} = [	ext{Ca}^{2+}][	ext{F}^-]^2$$

Question 12

What is the effect of adding NaF to a saturated solution of CaF$$_2$$?

Accepted Answer

The solubility of CaF$$_2$$ decreases due to the common ion effect.

Question 13

Which change will increase the solubility of Mg(OH)$$_2 in $$water?

Accepted Answer

Decreasing the pH

Question 14

If the equilibrium constant for the reaction $$2 	ext{X}(g) + 	ext{Y}(g) ightleftharpoons 3 	ext{Z}(g) is $$calculated as $$K_c = \frac{[	ext{Z}]^3}{[	ext{X}]^2[	ext{Y}]}$$, what is $$K_c if$$ $$[	ext{X}] = 2.0 M$$, $$[	ext{Y}] = 0.5 M$$, $$[	ext{Z}] = 4.0 M$$?

Accepted Answer

$$K_c = \frac{4.0^3$}{2.0^2$ 	imes 0.5} = 32$$

Question 15

Which of the following best explains why the solubility of an ionic compound containing a basic anion increases as the pH decreases?

Accepted Answer

Lower pH increases the concentration of H$$^+$$, which reacts with the basic anion, shifting equilibrium to dissolve more solid.

Question 16

Which of the following is true for the reaction $$	ext{CO}(g) + 	ext{H}_2	ext{O}(g) ightleftharpoons 	ext{CO}_2(g) + 	ext{H}_2(g) at $$equilibrium, given equal initial moles of CO and H$$_2O$$?

Accepted Answer

$$[	ext{CO}_2] \u003e [	ext{CO}]$$

Question 17

Which graph best represents the change in the reverse reaction rate after Cl$$_2 is $$added to a system at equilibrium for $$	ext{PCl}_5(g) ightleftharpoons 	ext{PCl}_3(g) + 	ext{Cl}_2(g)$$?

Accepted Answer

A graph showing a sudden increase in reverse rate that remains constant at the new rate.

Question 18

Which property is best represented by a particle diagram showing more ions from FeCO$$_3$$ dissolved compared to MnCO$$_3$$, given $$K_{sp,$$FeCO_3$$} \u003e K_{sp,$$MnCO_3$$}$$?

Accepted Answer

The molar solubility is greater for FeCO$$_3$$ compared to MnCO$$_3.$$

Question 19

Which of the following best illustrates what a particle diagram of NH$$_4NO$_3$$ dissolving in water is able to show?

Accepted Answer

That entropy increases when NH$$_4NO$_3$$ dissolves in water because the ions disperse in solution.

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