Question

What is the pH value of NaCl aqueous solution?
1. Acidic
2. Basic
3. Neutral
4. None of the above

Answer 1

Correct Answer - Option 3 : Neutral

Explanation:

pH: The negative of the logarithm to base 10 of the concentration of hydrogen ions, measured in moles per liter; a measure of acidity or alkalinity of a substance, which takes numerical values from 0 (maximum acidity) through 7 (neutral) to 14 (maximum alkalinity).

NaCl aqueous solution:

• NaCl aqueous solution is formed by NaOH and HCl which are strong base and strong acid respectively. So they will completely dissociate and neutralise each other. So the pH will be 7.

NaOH + HCl → NaCl + H₂O

• Strong acid + strong base (pH = 7) 
• Strong acid + weak base (pH < 7)
• Weak acid + strong base (pH > 7)
• Weak acid + weak base (pH < 7, or pH = 7, or pH > 7)

Hence we can conclude that pH value of NaCl aqueous solution is neutral.

• Strong base after neutralisation with weak acid forms basic solution
• Strang acid after neutralisation with weak base forms acidic solution.