Question

What is the molarity of \(\text{H}_2\text{SO}_4\) solution having \(\text{pH} = 4\) ?

• A. \(4\times 10^{-1} \text{M}\)
• B. \(4\times 10^{-2} \text{M}\)
• C. \(5\times 10^{-5} \text{M}\)
• D. \(1\times 10^{-4} \text{M}\)

Hint:

Find [H+] from pH, then divide by two because each H2SO4 gives two H+ ions.

Answer 1

The Correct Option is C

Step 1: Find the proton concentration:
pH $= 4$ means $[\text{H}^+] = 1.0 \times 10^{-4}$ mol/L.

Step 2: Relate to the acid:
If the acid concentration is $C$, complete dissociation gives $[\text{H}^+] = 2C$.
So $2C = 10^{-4}$, giving $C = 5 \times 10^{-5}$ M.

Final Answer:
The solution is $5 \times 10^{-5}$ M, option (C). \[ \boxed{5 \times 10^{-5}\ \text{M}} \]