Question

A---Write a net ionic equation to show that ethylamine, C₂H₅NH₂, behaves as a Bronsted-Lowry base in water.
-----Write a net ionic equation to show that codeine, C₁₈H₂₁O₃N, behaves as a Bronsted-Lowry base in water.
-----Write a net ionic equation to show that hydrofluoric acid behaves as a Brønsted-Lowry acid in water.

B---Write the K_a expression for an aqueous solution of acetic acid:

----Write the K_a expression for an aqueous solution of hydrofluoric acid:

----Write the K_a expression for an aqueous solution of hypochlorous acid:

C---In the laboratory, a general chemistry student measured the pH of a 0.402 M aqueous solution of formic acid, HCOOH to be 2.054.
Use the information she obtained to determine the K_a for this acid

-----In the laboratory, a general chemistry student measured the pH of a 0.402 M aqueous solution of acetic acid to be 2.587.

Use the information she obtained to determine the K_a for this acid.

----In the laboratory, a general chemistry student measured the pH of a 0.402 M aqueous solution of hydrofluoric acid to be 1.753.
Use the information she obtained to determine the K_a for this acid.

Answer 1

Part A) Write a net ionic equation to show that ethylamine, C₂H₅NH₂, behaves as a Bronsted-Lowry base in water.

C₂H₅NH₂(l) + H₂O(l) C₂H₅NH₃⁺(aq) + OH^-(aq)

1) Write a net ionic equation to show that codeine, C₁₈H₂₁O₃N, behaves as a Bronsted-Lowry base in water.

C₁₈H₂₁O₃N(aq) + H₂O(l) C₁₈H₂₁O₃NH⁺(aq) + OH^-(aq)

2) Write a net ionic equation to show that hydrofluoric acid behaves as a Brønsted-Lowry acid in water.

HF(aq) + H₂O(l) F^- (aq)+ H₃O⁺(aq)

Part B) Write the K_a expression for an aqueous solution of acetic acid:

CH₃COOH(aq) + H₂O(l)      CH₃COO^-(aq) + H₃O⁺(aq)

Ka = [CH₃COO^-][H₃O⁺]/[CH₃COOH]

1) Write the K_a expression for an aqueous solution of hydrofluoric acid:

HF(aq) + H₂O(l) F^-(aq) + H₃O⁺(aq)

Ka =[F^-][H₃O⁺]/[HF]

2) Write the K_a expression for an aqueous solution of hypochlorous acid:

HOCl(aq) + H₂O(l) OCl^-(aq) + H₃O⁺(aq)

Ka = [OCl^-][H₃O⁺]/[HOCl]

Part C)

1) In the laboratory, a general chemistry student measured the pH of a 0.402 M aqueous solution of formic acid, HCOOH to be 2.054. Use the information she obtained to determine the K_a for this acid

HCOOH(aq) + H₂O(l)      HCOO^-(aq) + H₃O⁺(aq)

pH = 2.054

Therefore, [H₃O⁺] = 10^-2.054 = 8.83 x 10^-3 M

[H₃O⁺] =8.83 x 10^-3 M
[HCOO^-] = 8.83 x 10^-3 M
[HCOOH] = 0.402 - 8.83 x 10^-3 M = 0.3931 M
Ka = (8.83 x 10^-3)²)/( 0.3931) = 1.983 x 10^-4

2) In the laboratory, a general chemistry student measured the pH of a 0.402 M aqueous solution of acetic acid to be 2.587. Use the information she obtained to determine the K_a for this acid.

CH₃COOH(aq) + H₂O(l)   CH₃COO^-(aq) + H₃O⁺(aq)

pH = 2.587

Therefore, [H₃O+] = 10^-2.587 = 2.588 x 10^-3 M

[H₃O⁺] = 2.588 x 10^-3 M
[CH₃COO^-] = 2.588 x 10^-3 M
[CH₃COOH] = 0.402 - 8.83 x 10^-3 M = 0.399 M
Ka = [(2.588 x 10^-3)²]/( 0.399) = 1. 67 x 10^-5

3) In the laboratory, a general chemistry student measured the pH of a 0.402 M aqueous solution of hydrofluoric acid to be 1.753. Use the information she obtained to determine the K_a for this acid.

HF(aq) + H₂O(l) F^-(aq) + H₃O⁺(aq)

pH = 1.753

Therefore, [H₃O⁺] = 10^-1.753 = 0.0176 M

[H₃O⁺] = 0.0176 M
[F^-] = 0.0176 M
[HF] = 0.402 - 0.0176 M = 0.384 M
Ka = [(0.0176)²]/( 0.384) = 8.059 x 10^-4