Question

$0.5$ g of fuming $H_{2}S{O}_4$ (oleum) is diluted with water. The solution requires $26.7$ mL of $0.4NNaOH$ for complete neutralization. Find the percentage of free $S{O}_3$ in the sample of oleum.

• A. $21\%$
• B. $33\%$
• C. $42\%$
• D. None of the above

Answer 1

The correct option is A $21\%$

As given,
Equivalents of $H_{2}S{O}_4=$ Equivalents of $NaOH$
$n\times 2=0.0267\times 0.4$
$n=0.0267\times 0.2$ moles of $H_{2}S{O}_4$
$N\times 98-0.5=$ mass of $H_{2}O$ added
Moles of $H_{2}O=$ Moles of $S{O}_3$
Percentage of $S{O}_3=20.72\%$