Question

An aqueous solution of ethanol has density $1.025g/mL$ and molarity $8M$. Calculate molality of this solution:

• A. $20.27m$
• B. $17.12m$
• C. $12.17m$
• D. $1.117m$

Answer 1

Answer: (C)

$8M$ means 8 moles of ethanol in $1L$ of solution

8 mole means $46\times 8=368g$ of ethanol

Let us consider one litre of this solution-

So, mass of solution $=1025g$

Mass of water $=1025-368=657g$

$8M=\frac{xg}{46\times 12}=368g/mol$

Molality $=\frac{368}{46\times 657}=12.17m$