Question

question 18 of 32
which of the following increases the h⁺ concentration in solution?
a. water
b. salt
c. an acid
d. a base

Explanation:

To determine which substance increases \( H^+ \) concentration in solution, we analyze each option:

• Option A: Water (\( H_2O \)) undergoes autoionization (\( H_2O

ightleftharpoons H^+ + OH^- \)) but has a very low \( H^+ \) concentration (neutral, \( [H^+] = 10^{-7} M \) at 25°C) and does not significantly increase \( H^+ \).

• Option B: Salt (e.g., \( NaCl \)) dissociates into ions (\( Na^+ \) and \( Cl^- \)) in solution. These ions do not directly contribute to \( H^+ \) concentration, so salt does not increase \( H^+ \).
• Option C: By definition, an acid is a substance that donates \( H^+ \) ions (or increases \( H^+ \) concentration) in an aqueous solution. For example, \( HCl

ightarrow H^+ + Cl^- \) increases \( [H^+] \).

• Option D: A base is a substance that accepts \( H^+ \) (or increases \( OH^- \) concentration), so it decreases \( H^+ \) concentration (e.g., \( NaOH

ightarrow Na^+ + OH^- \), and \( OH^- \) reacts with \( H^+ \) to form \( H_2O \), reducing \( [H^+] \)).

Answer:

C. An acid