Question

The strength of a ${10}^{-2}\text{M}N{a}_{2}C{O}_3$ solution in terms of its molality will be: $(\text{density of solution}=1.10{\text{g mL}}^{-1}$,$\text{molecular weight of}N{a}_{2}C{O}_3=106{\text{g mol}}^{-1})$

• A. $9.00\times {10}^{-3}$
• B. $1.50\times {10}^{-2}$
• C. $5.10\times {10}^{-3}$
• D. $11.2\times {10}^{-3}$

Answer 1

The correct option is A $9.00\times {10}^{-3}$

Given density of the solution $=1.10{gmL}^{-1}$
Again, ${10}^{-2}\text{M}N{a}_{2}C{O}_3={10}^{-2}molN{a}_{2}C{O}_3\text{in 1000 ml solvent}$

$\text{Mass of 1000 ml of the solution}=(1.10\times 1000)g=1100g$
$\text{Mass of solvent}=(1100-{10}^{-2}\times 106=1098.94g$
$\therefore Molality=\frac{{10}^{-2}}{1098.94}\times 1000\approx 9.00\times {10}^{-3}$