Physical Chemistry MCQ with Answers

251) 40 mL of 0.1M ammonia solution is mixed with 20 mL of 0.1M HCl. What is the pH of the mixture? (pK_b of ammonium solution is 4.74)

Answer is:

9.26

252) In an equimolar mixture of NH₄Cl and NH₄OH, the ratio of concentration of salt to the base in is increased ten fold. pOH of the solution:

Answer is:

Increases by one

Explanation:

pOH = pK_b + log 10

253) To an Ag₂CrO₄ solution, CrO₄²⁻ ions are added. This results in:

Answer is:

Decrease in Ag⁺ concentration

Explanation:

On adding CrO₄²⁻, the equilibrium shifts to the left due to increase in concentration of CrO₄²⁻ ions. Hence, the concentration of Ag decreases in the solution.

254) The solubility product of iron (III) hydroxide is 1.6 x 10⁻³⁹. If X is the solubility of iron (III) hydroxide, then which one of the following expressions can be used to calculate X?

Answer is:

K_sp = 27X⁴

Explanation:

The solubility product of a sparingly soluble salt at a given temperature maybe defined as the product of the molar concentration of its ions each raised to the power equal to its number of ions present in the equation representing the dissociation of one molecule of the salt.

255) pH of a buffer solution decreases by 0.02 units when 0.12 gm of acetic acid is added to 250 mL of a buffer solution of acetic acid and potassium acetate at 27^oC. The buffer capacity of the solution is:

Answer is:

251) 40 mL of 0.1M ammonia solution is mixed with 20 mL of 0.1M HCl. What is the pH of the mixture? (pKb of ammonium solution is 4.74)

9.26

252) In an equimolar mixture of NH4Cl and NH4OH, the ratio of concentration of salt to the base in is increased ten fold. pOH of the solution:

Increases by one

253) To an Ag2CrO4 solution, CrO42− ions are added. This results in:

Decrease in Ag+ concentration

254) The solubility product of iron (III) hydroxide is 1.6 x 10−39. If X is the solubility of iron (III) hydroxide, then which one of the following expressions can be used to calculate X?

Ksp = 27X4

255) pH of a buffer solution decreases by 0.02 units when 0.12 gm of acetic acid is added to 250 mL of a buffer solution of acetic acid and potassium acetate at 27oC. The buffer capacity of the solution is:

0.4

251) 40 mL of 0.1M ammonia solution is mixed with 20 mL of 0.1M HCl. What is the pH of the mixture? (pK_b of ammonium solution is 4.74)

252) In an equimolar mixture of NH₄Cl and NH₄OH, the ratio of concentration of salt to the base in is increased ten fold. pOH of the solution:

253) To an Ag₂CrO₄ solution, CrO₄²⁻ ions are added. This results in:

Decrease in Ag⁺ concentration

254) The solubility product of iron (III) hydroxide is 1.6 x 10⁻³⁹. If X is the solubility of iron (III) hydroxide, then which one of the following expressions can be used to calculate X?

K_sp = 27X⁴

255) pH of a buffer solution decreases by 0.02 units when 0.12 gm of acetic acid is added to 250 mL of a buffer solution of acetic acid and potassium acetate at 27^oC. The buffer capacity of the solution is: