Question

Formic acid, which is a component of insect venom, has a ka = 1.8 ´ 10-4. what is the [h3o+] in a solution that is initially 0.10 m formic acid, hcooh? question 24 options: 1) 4.2 ´ 10-3 m 2) 1.8 ´ 10-5 m 3) 8.4 ´ 10-3 m 4) 1.8 ´ 10-6 m 5) 1.8 ´ 10-4 m

Answer 1

Answer is: concentratio of H₃O⁺ ions is 4.2·10⁻³ M.
Chemical reaction: HCOOH(aq) + H₂O(l) ⇄ HCOO⁻(aq) + H₃O⁺(aq).
c(HCOOH) = 0,1 M.
[H₃O⁺] = [HCOO⁻] = x.
[HCOOH] = 0,1 M - x.
Ka = [H₃O⁺] · [HCOO⁻] / [HCOOH].
0,00018 = x² / (0,1 M - x).
Solve quadratic equation: x = [H₃O⁺] = 0,0042 M.