Acids, Bases and Salts - Numerical Applications for Exams

Acids, Bases and Salts - Numerical Applications

Q. How many grams of sodium chloride are needed to prepare 0.5 L of a 0.2 M solution?

A. 5.84 g
B. 11.68 g
C. 2.92 g
D. 0.58 g

Solution

Molar mass of NaCl = 58.44 g/mol. Moles needed = 0.2 M * 0.5 L = 0.1 moles. Mass = moles * molar mass = 0.1 * 58.44 g = 5.844 g.

Correct Answer: B — 11.68 g

Q. How many moles of potassium hydroxide are needed to neutralize 0.1 moles of hydrochloric acid?

A. 0.05
B. 0.1
C. 0.2
D. 0.3

Solution

The reaction between KOH and HCl is 1:1. Therefore, 0.1 moles of HCl will require 0.1 moles of KOH.

Correct Answer: B — 0.1

Q. If 25 mL of 0.5 M acetic acid is mixed with 25 mL of 0.5 M sodium acetate, what is the resulting pH of the buffer solution?

A. 4.76
B. 5.00
C. 5.76
D. 6.00

Solution

Using the Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]). pKa of acetic acid is approximately 4.76. Since [A-] = [HA], pH = 4.76.

Correct Answer: A — 4.76

Q. If 50 mL of 0.1 M sulfuric acid is neutralized by sodium hydroxide, how many moles of NaOH are required?

A. 0.005
B. 0.01
C. 0.02
D. 0.03

Solution

H2SO4 dissociates to give 2 H+ ions. Moles of H2SO4 = 0.1 M * 0.050 L = 0.005 moles. Therefore, moles of NaOH required = 0.005 moles * 2 = 0.01 moles.

Correct Answer: B — 0.01

Q. What is the concentration of hydroxide ions in a solution with a pH of 11?

A. 1 x 10^-3 M
B. 1 x 10^-4 M
C. 1 x 10^-5 M
D. 1 x 10^-6 M

Solution

pOH = 14 - pH = 14 - 11 = 3. [OH-] = 10^-pOH = 10^-3 M.

Correct Answer: A — 1 x 10^-3 M

Q. What is the equivalent weight of sulfuric acid (H2SO4) for the purpose of neutralization?

A. 49 g
B. 98 g
C. 24.5 g
D. 196 g

Solution

Equivalent weight = molar mass / n, where n = number of H+ ions. Molar mass of H2SO4 = 98 g/mol, n = 2. Therefore, equivalent weight = 98 g / 2 = 49 g.

Correct Answer: C — 24.5 g

Q. What is the molarity of a sodium hydroxide solution if 0.4 moles are dissolved in 2 liters of water?

A. 0.2 M
B. 0.4 M
C. 0.5 M
D. 0.8 M

Solution

Molarity (M) = moles of solute / liters of solution. Here, M = 0.4 moles / 2 L = 0.2 M.

Correct Answer: B — 0.4 M

Q. What is the pH of a 0.001 M solution of sodium bicarbonate (NaHCO3)?

A. 8.4
B. 7.0
C. 9.0
D. 6.5

Solution

Sodium bicarbonate is a weak base. The pH can be estimated to be around 8.4 for a 0.001 M solution.

Correct Answer: A — 8.4

Q. What is the pH of a 0.01 M hydrochloric acid solution?

A. 1
B. 2
C. 3
D. 4

Solution

The pH of a strong acid like HCl can be calculated using the formula pH = -log[H+]. For 0.01 M HCl, pH = -log(0.01) = 2.

Correct Answer: A — 1

Q. What is the pH of a solution that has a hydrogen ion concentration of 1 x 10^-7 M?

A. 7
B. 0
C. 14
D. 1

Solution

pH = -log[H+] = -log(1 x 10^-7) = 7.

Correct Answer: A — 7

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