Q: If the solubility of $$AgCl at 25$$°C is $$0.00019 g $$per $$100 mL$$, what is the value of $$K_{ps}$$? (Molar mass $$AgCl = 143 g/$$mol)

$$K_{ps} = 1.8 \times 10$$^{-10}$$

Question 1

Which of the following pairs can be combined to form a buffer solution?

Accepted Answer

0.10 M NaCN and 0.10 M HCN

Question 2

Given the following acids and their $$pK_a$$ values, which is the most suitable to prepare a buffer with $$pH = 5.02$$?

Accepted Answer

HC2H3O2, $$pK_a = 4.74$$

Question 3

Calculate the $$pH of a $$buffer solution prepared by dissolving 13.02 g of sodium acetate ($$NaC_2H_3O_2) $$and 15.40 g of acetic acid ($$HC_2H_3O_2) in $$water to make 500 mL of solution. ($$pK_a = 4.74$$, molar masses: $$NaC_2H_3O_2 = 82.03 g/$$mol, $$HC_2H_3O_2 = 60.05 g/$$mol)

Accepted Answer

$$pH = 4.53$$

Question 4

Which of the following statements about the solubility product constant ($$K_{ps}) is $$correct?

Accepted Answer

A small $$K_{ps}$$ value indicates a salt is poorly soluble.

Question 5

If the solubility of $$AgCl at 25$$°C is $$0.00019 g $$per $$100 mL$$, what is the value of $$K_{ps}$$? (Molar mass $$AgCl = 143 g/$$mol)

Accepted Answer

$$K_{ps} = 1.8 	imes 10$$^{-10}$$

Question 6

A solution contains $$[Ba$$^{2+}$$] = 1.0 	imes 10$$^{-3}$$ M and $$[$$SO_4$$^{2-}] = 1.0 	imes $$10^{-4} M. $$The $$K_{ps}$$ for $$BaSO_4 is$$ $$1.0 	imes 10$$^{-10}$$. Will $$BaSO_4$$ precipitate?

Accepted Answer

Yes, because the ionic product is greater than $$K_{ps}.$$

Question 7

What is the effect of adding a common ion to a solution containing a slightly soluble salt?

Accepted Answer

It decreases the solubility of the salt.

Question 8

Calculate the solubility ($$s) of$$ $$CaF_2 if$$ $$K_{ps} = 4.0 	imes 10$$^{-8}$$.

Accepted Answer

$$s = 2.0 	imes 10$$^{-3}$$

Question 9

Which of the following will increase the solubility of $$AgCN in $$water?

Accepted Answer

Adding $$HNO_3$$

Question 10

A solution contains $$1.0 	imes 10$$^{-4}$$ M Fe$$^{2+}$$. What concentration of S$$^{2-}$$ is needed to begin precipitation of $$FeS$$? (K$$_{ps} = 5.0 	imes $$10^{-18})$$

Accepted Answer

$$5.0 	imes 10$$^{-14}$$ M

Question 11

Which of the following is NOT a factor that affects precipitation equilibrium?

Accepted Answer

Addition of a non-electrolyte

Question 12

What is the $$K_{ps}$$ expression for $$Ag_2S$$?

Accepted Answer

$$K_{ps} = [Ag^+]^2 [S$$^{2-}$$]$$

Question 13

If the ionic product ($$PI) $$for a salt is less than $$K_{ps}$$, what will happen?

Accepted Answer

No precipitate will form.

Question 14

Which of the following best describes the effect of a non-common ion (ion-diverso) on the solubility of a slightly soluble salt?

Accepted Answer

It increases the solubility.

Question 15

A buffer solution is prepared by mixing $$0.5130 M$$ $$HC_2H_3O_2$$ and $$0.3174 M$$ $$NaC_2H_3O_2. $$What is the $$pH of $$the solution? ($$pK_a = 4.74)$$

Accepted Answer

$$pH = 4.53$$

Question 16

Which of the following equations correctly represents the dissolution of $$CaF_2$$ and its $$K_{ps}$$ expression?

Accepted Answer

$$CaF_2$$ \rightarrow $$Ca^{2+}$$ + $$2F^{-}$$; $$K_{ps} = [Ca$$^{2+}$$][F$$^{-}$$]^2$$

Question 17

Which of the following will NOT form a buffer solution?

Accepted Answer

A strong acid and its conjugate base

Question 18

If $$K_{ps}$$ for $$Ag_2CrO_4 is$$ $$1.3 	imes 10$$^{-12}$$, what is the molar solubility (s$) of Ag_2$$CrO_4$$?

Accepted Answer

$$s = 6.9 	imes 10$$^{-5}$$

Question 19

Which of the following changes will decrease the ionic product ($$PI) $$and prevent precipitation?

Accepted Answer

Adding more solvent

Buffer Solutions and Solubility Equilibria in Analytical Chemistry

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