Q: A buffer is prepared by mixing 0.20 mol of NH3 and 0.20 mol of NH4Cl in 1.0 L of solution. Which equation best describes the pH of this buffer?

$$\text{pOH} = \text{p}K_b + \log \frac{[\text{NH}_4^+]}{[\text{NH}_3]}$$

Q: What is the $$K_{sp}$$ expression for $$\text{Ca}_3(\text{PO}_4)_2$$?

$$K_{sp} = [\text{Ca}^{2+}]^3[\text{PO}_4$$^{3-}$$]^2$$

Q: Which of the following is the correct Henderson-Hasselbalch equation for a buffer made from a weak acid HA and its conjugate base A$$^-$$?

$$\text{pH} = \text{p}K_a + \log \frac{[\text{A}^-]}{[\text{HA}]}$$

Question 1

Which of the following combinations would create a buffer solution that is effective at resisting changes in pH near 4.7?

Accepted Answer

0.25 M CH3COOH and 0.25 M CH3COONa

Question 2

A buffer is prepared by mixing 0.20 mol of NH3 and 0.20 mol of NH4Cl in 1.0 L of solution. Which equation best describes the pH of this buffer?

Accepted Answer

$$	ext{pOH} = 	ext{p}K_b + \log \frac{[	ext{NH}_4^+]}{[	ext{NH}_3]}$$

Question 3

Which of the following best explains why blood pH must be tightly regulated?

Accepted Answer

Because deviations from normal pH impair oxygen transport and can cause muscle weakness or cramps

Question 4

Calculate the pH of a buffer solution containing 0.050 M lactic acid and 0.060 M sodium lactate. $$K_a = 1.4 	imes 10$$^{-4}$$.

Accepted Answer

$$	ext{pH} = 3.92$$

Question 5

Which of the following statements about buffer capacity is correct?

Accepted Answer

Buffer capacity increases as the total concentration of buffer components increases

Question 6

A 1.0 L buffer contains 0.40 mol NaH2PO4 and 0.25 mol Na2HPO4. What is the pH after adding 0.10 mol NaOH? ($$K_a = 6.2 	imes 10$$^{-8}$$)

Accepted Answer

$$	ext{pH} = 7.28$$

Question 7

Which indicator would be most suitable for detecting the equivalence point in a titration with an expected equivalence pH of 7.0?

Accepted Answer

Bromothymol blue

Question 8

What is the $$K_{sp}$$ expression for $$	ext{Ca}_3(	ext{PO}_4)_2$$?

Accepted Answer

$$K_{sp} = [	ext{Ca}^{2+}]^3[	ext{PO}_4$$^{3-}$$]^2$$

Question 9

A solution is prepared by mixing 25.0 mL of 0.0025 M HCl and 10.0 mL of 0.010 M AgNO3. Will AgCl precipitate? ($$K_{sp} = 1.8 	imes 10$$^{-10}$$)

Accepted Answer

Yes, because $$Q \u003e K_{sp}$$

Question 10

Which salt will precipitate first when HCl is added to a solution containing 0.010 M Cu$$^+$$ and 0.500 M Pb$$^{2+}$$? ($$K_{sp}$$ for PbCl$$_2$$ = $$1.7 	imes 10$$^{-5}$$, K$$_{sp}$$ for CuCl = 1.9$$ 	imes $$10^{-7})$$

Accepted Answer

CuCl

Question 11

Which of the following best describes the common ion effect?

Accepted Answer

The solubility of a salt decreases when a common ion is added

Question 12

What is the molar solubility of AgCl in pure water if $$K_{sp} = 1.8 	imes 10$$^{-10}$$?

Accepted Answer

$$1.3 	imes 10$$^{-5}$$ M

Question 13

Which of the following is true about amphoteric oxides and hydroxides?

Accepted Answer

They are soluble in both strong acids and strong bases

Question 14

A student titrates 25.0 mL of 0.234 M NaOH with 0.0875 M H$$_2SO$_4. $$What volume of acid is required to reach the equivalence point?

Accepted Answer

33.4 mL

Question 15

Which of the following best describes the pH at the equivalence point when titrating a weak acid with a strong base?

Accepted Answer

The pH is greater than 7.0

Question 16

Which of the following is the correct Henderson-Hasselbalch equation for a buffer made from a weak acid HA and its conjugate base A$$^-$$?

Accepted Answer

$$	ext{pH} = 	ext{p}K_a + \log \frac{[	ext{A}^-]}{[	ext{HA}]}$$

Question 17

Which of the following best describes what happens when a small amount of strong acid is added to a buffer solution?

Accepted Answer

The buffer's weak base component reacts with the acid, minimizing the pH change

Question 18

Which of the following is the correct relationship between the molar solubility (S) and $$K_{sp}$$ for Mn(OH)$$_2$$?

Accepted Answer

$$K_{sp} = [S][2S]^2 = 4S^3$

Aqueous Equilibria: Buffers, Titrations, and Solubility

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