Question

How many grams of Mohr's salt is required to make a 250 mL solution having a concentration of 4 M?
Molar mass of Mohr's salt $=392gmo{l}^{-1}$

• A. $392\text{g}$
• B. $39.2\text{g}$
• C. $3.92\text{g}$
• D. $0.392\text{g}$

Answer 1

The correct option is A $392\text{g}$

Mohr's salt formula is $\left(N{H}_4{)}_{2}Fe\right(S{O}_4{)}_2.6H_{2}O$
$Molarity=\frac{\text{Moles of solute}}{\text{Total volume of solution in mL}}\times 10004M=\frac{\text{moles of solute}}{250}\times 1000$
Moles of solute= $1$ mol
Mass of 1 mol of Mohr's salt $=1\times 392=392$ g