Question

Molarity and molality of a solution of a liquid (mol wt. = 50) in aqueous solution is 9 and 10 respectively. What is the density of solution?

• A. $1g/cc$
• B. $0.95g/cc$
• C. $1.05g/cc$
• D. $1.35g/cc$

Answer 1

The correct option is D $1.35g/cc$

Molarity= $9M$

Molality= $10$ molal

Molarity is the number of moles of solute dissolved per $1000ml$ of solution.

Molality is the number of moles of solute dissolved per $1000g$ of solvent.

$9$ moles of the compound are present in $1000ml$ of solution. Then $1$ mole of compound would be present in:- $1000/9=110ml$

$10$ moles of compound are present in $1000kg$ of solvent

$1$ mole of compound would be present in,

Mass of solute $10\times 50=500g$

Total $1000+500=1500/10=150$ per $g$

Density= $\frac{Mass}{Volume}=\frac{150}{110}=1.35g/cc$