Q: A 45.0 mL sample of 0.0950 M NaOH is titrated with 0.105 M HCl. How many mL of HCl are required to reach the equivalence point?

$$V = \frac{0.0450 \times 0.0950}{0.105} = 0.0407 L$$ $$= 40.7 mL$$

Question 1

Which of the following best explains the common-ion effect observed when sodium acetate is added to a solution of acetic acid?

Accepted Answer

The addition of CH3COO- shifts the equilibrium to the left, decreasing [H+].

Question 2

A buffer solution is prepared by mixing 0.100 mol of NH3 and 0.100 mol of NH4Cl in 1.0 L of water. What will happen to the pH if a small amount of HCl is added?

Accepted Answer

The pH will decrease slightly.

Question 3

Which equation is used to calculate the pH of a buffer solution containing a weak acid and its conjugate base?

Accepted Answer

$$\mathrm{pH} = \mathrm{p}K_a + \log \left( \frac{[\mathrm{A}^-]}{[\mathrm{HA}]} \right)$$

Question 4

A buffer is made by mixing 0.15 mol of propionic acid (C2H5CO2H) and 0.10 mol of sodium propionate (C2H5CO2Na) in 1.20 L. If 0.01 mol of NaOH is added, what is the first step in calculating the new pH?

Accepted Answer

Calculate the new concentrations of acid and base after the reaction with NaOH.

Question 5

During the titration of a strong acid with a strong base, what is true at the equivalence point?

Accepted Answer

The pH is exactly 7 because only water and a neutral salt are present.

Question 6

A 45.0 mL sample of 0.0950 M NaOH is titrated with 0.105 M HCl. How many mL of HCl are required to reach the equivalence point?

Accepted Answer

$$V = \frac{0.0450 	imes 0.0950}{0.105} = 0.0407 L$$ $$= 40.7 mL$$

Question 7

Which of the following statements about buffer capacity is correct?

Accepted Answer

A buffer with higher concentrations of acid and base can neutralize more added acid or base before the pH changes significantly.

Question 8

What is the pH at the halfway point to the equivalence point in the titration of a weak acid with a strong base?

Accepted Answer

The pH equals the pKa of the weak acid.

Question 9

Which of the following best describes the effect of adding a common ion to a saturated solution of a sparingly soluble salt?

Accepted Answer

The solubility of the salt decreases.

Question 10

Given $$K_{sp}$$ for $$Ca_3$$($$PO_4)_2$ is 2.0$$ 	imes $$10^{-29}$$, what is the correct expression for the solubility product?

Accepted Answer

$$K_{sp} = [Ca$$^{2+}$$]^3 [PO_4$^{3-}]^2$$

Question 11

A solution is saturated with lead(II) iodide at 25°C and contains 0.54 g of PbI2 in 1.00 L. What is the first step to calculate the $$K_{sp} of $$PbI2?

Accepted Answer

Convert grams of PbI2 to moles to find the molar solubility.

Question 12

Which of the following is true about the titration curve of a weak acid with a strong base compared to a strong acid with a strong base?

Accepted Answer

The pH at the equivalence point is greater than 7 for the weak acid titration.

Question 13

If the $$K_{sp} of$$ $$BaSO_4 is$$ $$1.5 	imes 10$$^{-10}$$ and the K$$_{sp}$$ of Ag_2SO_4$ is 1.5$$ 	imes $$10^{-5}$$, which salt is more soluble in water?

Accepted Answer

$$Ag_2SO_4 is $$more soluble because it has a higher $$K_{sp}.$$

Question 14

What happens to the solubility of $$CaF_2$$ when $$NaF is $$added to the solution?

Accepted Answer

The solubility of $$CaF_2$$ decreases due to the common-ion effect.

Question 15

A buffer is prepared by partially neutralizing a weak acid with a strong base. Which of the following best describes the resulting solution?

Accepted Answer

It contains both the weak acid and its conjugate base in significant amounts.

Question 16

Which of the following is a correct step in calculating the pH after adding a strong acid to a buffer solution?

Accepted Answer

Subtract the moles of strong acid added from the moles of conjugate base present.

Question 17

Which of the following best describes the relationship between $$K_{sp}$$ and molar solubility?

Accepted Answer

$$K_{sp} is $$the product of the molar concentrations of the ions, each raised to the power of their coefficients in the balanced equation.

Aqueous Equilibria: Buffers, Titrations, and Solubility

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