Question

Which of the following turns blue litmus red?

• A. NaOH
• B. Ca(OH)\(_2\)
• C. H\(_2\)SO\(_4\)
• D. KOH

Hint:

Litmus test:
• Acid $\rightarrow$ Blue litmus turns red.
• Base $\rightarrow$ Red litmus turns blue.

Answer 1

The Correct Option is C

Concept: Litmus paper is an acid--base indicator.
• Acids turn blue litmus red.
• Bases turn red litmus blue.

Step 1: Identify the nature of each substance.

• NaOH -- Base
• Ca(OH)\(_2\) -- Base
• H\(_2\)SO\(_4\) -- Strong acid
• KOH -- Base

Step 2: Choose the correct option.
Since sulfuric acid is an acid, \[ \boxed{\text{H}_2\text{SO}_4} \] turns blue litmus paper red.

Step 3: Final conclusion.
Hence, the correct answer is \[ \boxed{\text{H}_2\text{SO}_4.} \]