Question

Which or the following solutions would have the highest concentration of hydronium ion and why?

A)1.0×10^-3 M HCl
B)1.0×10^-3 M HC2 H3 O2
C)0.050 M HCl
D)0.050 M HC2 H3 O2

(I already know that the answer is C I just don't know why)

Answer 1

Answer is: C)0.050 M HCl.
Chemical reaction 1: HCl(aq) + H₂O(l) → H₃O⁺(aq) + Cl⁻(aq).
Chemical reaction 2: CH₃COOH(aq) + H₂O(l) ⇄ H₃O⁺(aq) + CH₃COO⁻(aq).
Hydrochloric acid (HCl) is strong acid, which means that concencentration of hydronium ions are equal as concentration of hydrochloric acid:
A) c(HCl) = c(H₃O⁺) = 0.001 M.
C) c(HCl) = c(H₃O⁺) = 0.050 M is greater than A.
Acetic acid (CH₃COOH) is weak acid and does not dissociate completely as HCl, so concentration of hydronium ion in this solutions are very low.