Question

Which of the following is a true statement about acids and bases?

Answer 1

Answer: The correct answer is 'a base gives off hydroxide ions'.

Explanation:

• Bases have pH more than seven.
• They give hydroxide ions,$OH^-$.

$BOH(aq)\rightarrow B^+(aq)+OH^-(aq)$

• Acids have pH lower than seven.
• They give hydronium ions,$H^+$.

$HA(aq)\rightarrow H^+(aq)+A^-(aq)$

Answer 2

Answer: A base gives off hydroxide ions.

Explanation: According to Arrhenius concept, a base is defined as a substance which donates hydroxide ions $(OH^-)$ when dissolved in water and an acid is defined as a substance which donates hydronium ions $(H_3O^+)$ in water.

According to the Bronsted Lowry conjugate acid-base theory, an acid is defined as a substance which donates protons and a base is defined as a substance which accepts protons.

Acids have pH values ranging from 1 to 6.9, neutral solutions have pH of 7 and bases have pH ranging from 7.1 to 14.

A substance that increases the hydroxide ion concentration of a solution is an Arrhenius base.

$NaOH\rightarrow Na^++OH^-$