Question

40% $w/W$ $Ca(OH{)}_2$ solution has a molarity of 7.8 M. Calculate the density of the solution.

• A. 1.03 g /cc
• B. 1.04 g/ cc
• C. 1.54 g/cc
• D. 1.44 g/cc

Answer 1

Answer: (D)

1.44 g/cc

Let the density of solution be $=xg/cc$

Molarity $=7.8M$

Molecular mass of $Ca(OH{)}_2=40+34=74$

Mass of solute $=40g$

Molarity $=\frac{\text{Mass of solute}}{\text{Molecular mass of solute}}\times \frac{1000}{\left(\frac{100}{x}\right)}$

$(\because v=\frac{m}{d})$

$7.8=\frac{40}{74}\times \frac{1000}{100}\times x$

$x=1.44g/cc$

Hence, option D is correct.