Question

A hydrate of $N{a}_{2}S{O}_3$ has $50\%$ water by mass. It is

• A. $N{a}_{2}S{O}_3\cdot 5H_{2}O$
• B. $N{a}_{2}S{O}_3\cdot 6H_{2}O$
• C. $N{a}_{2}S{O}_3\cdot 7H_{2}O$
• D. $N{a}_{2}S{O}_3\cdot 2H_{2}O$

Answer 1

Answer: (C)

$N{a}_{2}S{O}_3:H_{2}O\equiv 50:50(Mw$ of $N{a}_{2}S{O}_3=126)$
Mole: $\frac{50}{126}:\frac{50}{18}$
Ratio: $1:7$