Question

A solution of \( \text{H}_2\text{SO}_4 \) is 31.4% \( \text{H}_2\text{SO}_4 \) by mass and has a density of \( 1.25 \, \text{g/mL} \). The molarity of the \( \text{H}_2\text{SO}_4 \) solution is _____ M (nearest integer).
[Given molar mass of \( \text{H}_2\text{SO}_4 = 98 \, \text{g/mol} \)]

Answer 1

Correct Answer: 4

To find the molarity (M), use the formula:

\( M = \frac{n_{\text{solute}}}{V} \times 1000 \)

Given that the solution is 31.4% \( H_2SO_4 \), with a density of 1.25 g/mL:

Step 1: Calculate the mass of \( H_2SO_4 \) in 100 g of solution:

Mass of \( H_2SO_4 = 31.4 \, \text{g} \)

Step 2: Convert this to moles:

\( \frac{31.4}{98} = 0.32 \, \text{mol} \)

Step 3: Find the volume of the solution:

\( \text{Volume} = \frac{\text{Mass of solution}}{\text{Density}} = \frac{100}{1.25} = 80 \, \text{mL} \)

Step 4: Calculate molarity:

\( M = \frac{0.32 \, \text{mol}}{80 \, \text{mL}} \times 1000 = 4.005 \approx 4 \, \text{M} \)

So, the correct answer is: 4M