Question

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

An acid has a pH of 7.1.
An acid accepts hydrogen ions.
A base has a pH of 7.
A base gives off hydroxide ions.

Answer 1

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

Step-by-step 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^-`