Question

The strength of $10^{- 2 \, }M \, Na_{2}CO_{3}$ solution interms of molality will be (density of the solution $=1.10 \, gml^{- 1}$ )
$\left(\text{M} . \left(\text{wt Na}\right)_{2} \left(\text{CO}\right)_{3} = 106\right)$

• A. $9\times 10^{- 3}$
• B. $1.15\times 10^{- 2}$
• C. $5.1\times 10^{- 3}$
• D. $11.2\times 10^{- 3}$

Answer 1

Answer: (A)

$m=\frac{17 \times 1000}{\left(\right. 1000 \times d - 17 \times M . W \left.\right)}$
$m=\frac{1 0^{- 2} \times 1000}{1000 \times 1.1 - 1 0^{- 2} \times 106}=\frac{10}{1099.4}=9\times 10^{- 3}$