Calculate the molar mass of sulphuric acid (H2SO4).
This chemistry question involves key chemical concepts and calculations. The detailed solution below walks through each step, from identifying the reaction type to computing the final answer.
ScanSolve AI Answer
Step 1: Calculate the molar mass of sulphuric acid ($\text{H}_2\text{SO}_4$).
The atomic masses are given as H=1, S=32, O=16.
$$ \text{Molar mass of H}_2\text{SO}_4 = (2 \times 1) + 32 + (4 \times 16) = 2 + 32 + 64 = 98 \text{ g/mol} $$
Step 2: Calculate the moles of $\text{H}_2\text{SO}_4$ required for the desired solution.
The target solution is 250 cm$^3$ (which is 0.250 dm$^3$) of 0.2 M $\text{H}_2\text{SO}_4$.
$$ \text{Moles of H}_2\text{SO}_4 = \text{Molarity} \times \text{Volume (in dm}^3\text{)} $$
$$ \text{Moles of H}_2\text{SO}_4 = 0.2 \text{ mol/dm}^3 \times 0.250 \text{ dm}^3 = 0.05 \text{ mol} $$
Step 3: Calculate the mass of $\text{H}_2\text{SO}_4$ corresponding to these moles.
$$ \text{Mass of H}_2\text{SO}_4 = \text{Moles} \times \text{Molar mass} $$
$$ \text{Mass of H}_2\text{SO}_4 = 0.05 \text{ mol} \times 98 \text{ g/mol} = 4.9 \text{ g} $$
Step 4: Calculate the volume of pure sulphuric acid (liquid) required using its density.
The density of pure sulphuric acid is 1.84 g/cm$^3$.
$$ \text{Volume} = \frac{\text{Mass}}{\text{Density}} $$
$$ \text{Volume of pure H}_2\text{SO}_4 = \frac{4.9 \text{ g}}{1.84 \text{ g/cm}^3} \approx 2.663 \text{ cm}^3 $$
Step 5: Select the closest option.
The calculated volume is approximately $2.66 \text{ cm}^3$, which matches option B.
The final answer is $\boxed{\text{B. 2.66}}$.
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