Q. What is [H⁺] in mol/L of a solution that is 0.20 M in CH₃COONa and 0.10 M in CH₃COOH? Ka for CH₃COOH = 1.8 × 10⁻⁵.
A) 9.0 × 10⁻⁶
B) 3.5 × 10⁻⁴
C) 1.1 × 10⁻⁵
D) 1.8 × 10⁻⁵
Explanation
[Solution from source] Buffer: [H⁺] = K_a[CH₃COOH]/[CH₃COO⁻] = 1.8 × 10⁻⁵ × 0.10/0.20 = 9.0 × 10⁻⁶ M. 1.8 × 10⁻⁵ would hold only if the acid and salt concentrations were equal. Answer (1).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.