Question

Which among the following has highest pH?

• A. 1 M H₂SO₄
• B. 1 M HCl
• C. 0.1 M NaOH
• D. 1 M NaOH

Answer 1

The Correct Option is D

The pH scale measures the acidity or alkalinity of a solution. A higher pH value indicates a more alkaline or basic solution, while a lower pH value indicates a more acidic solution. Among the options provided: 
(A) 1 M H₂SO₄: Sulfuric acid (H₂SO₄) is a strong acid and has a low pH. It is highly acidic. 
(B) 1 M HCl: Hydrochloric acid (HCl) is also a strong acid and has a low pH. It is highly acidic. 
(C) 0.1 M NaOH: Sodium hydroxide (NaOH) is a strong base and has a high pH. It is alkaline. 
(D) 1 M NaOH: Sodium hydroxide (NaOH) is a strong base and has a high pH. It is alkaline. 
Comparing options (C) and (D), both solutions contain the same base, sodium hydroxide (NaOH), but option (D) has a higher concentration (1 M) compared to option (C) (0.1 M). Since pH is a logarithmic scale, a higher concentration of a strong base will result in a higher pH value. 
Therefore, option (D) 1 M NaOH has the highest pH among the given options.

Answer 2

Correct Answer: 1 M NaOH 

Explanation:
The pH scale measures the concentration of hydrogen ions \([H^+]\) in a solution. It ranges from 0 to 14:
- Acids have pH < 7
- Bases have pH > 7
- Stronger bases have higher pH

Given solutions:
- 1 M H₂SO₄ and 1 M HCl are strong acids → very low pH
- 0.1 M NaOH is a dilute strong base → moderate high pH
- 1 M NaOH is a concentrated strong base → highest pH among the given

Therefore, 1 M NaOH has the highest pH.