What will be the pH of an aqueous solution of 1M ammonium formate assuming complete dissociation? (pK<sub>a</sub> for formic acid = 3.8 and pK<sub>b</sub> for ammonia = 4.8)

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249

Physical Chemistry MCQ with Answers

249) What will be the pH of an aqueous solution of 1M ammonium formate assuming complete dissociation? (pK_a for formic acid = 3.8 and pK_b for ammonia = 4.8)

3.8

4.8

6.5

8.5

Answer is:

6.5

Explanation:

pH = 7 + 0.5pK_a − 0.5pK_b

Physical Chemistry MCQ with Answers

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250) pH of 0.02M solution of pyridinium hydrochloride (a salt of strong acid and weak base) is 3.44. The ionisation constant of pyridine is:

1.51 x 10⁻⁷

1.51 x 10⁻⁸

1.51 x 10⁻⁹

1.51 x 10⁻¹⁰

Answer is:

1.51 x 10⁻⁹

Explanation:

pH = −0.5 [log K_w − log K_b + log C]

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)

4.74

2.26

9.26

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:

Increases ten fold

Decreases ten fold

Decreases by one

Increases by one

Answer is:

Increases by one

Explanation:

pOH = pK_b + log 10

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

Increase in Ag⁺ concentration

Decrease in Ag⁺ concentration

Increase in the solubility product

Decrease in the solubility product

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.

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249) What will be the pH of an aqueous solution of 1M ammonium formate assuming complete dissociation? (pKa for formic acid = 3.8 and pKb for ammonia = 4.8)

6.5

Physical Chemistry MCQ with Answers

Related Physical Chemistry MCQ with Answers

250) pH of 0.02M solution of pyridinium hydrochloride (a salt of strong acid and weak base) is 3.44. The ionisation constant of pyridine is:

1.51 x 10−9

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

Physical Chemistry MCQ with Answers

249) What will be the pH of an aqueous solution of 1M ammonium formate assuming complete dissociation? (pK_a for formic acid = 3.8 and pK_b for ammonia = 4.8)

1.51 x 10⁻⁹

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