Question

$10mL$ of $6$ (w/v) aqueous urea solution is diluted such that its molarity becomes $0.1M$. Volume of water added to make such solution is:

• A. $70mL$
• B. $80mL$
• C. $90mL$
• D. $990mL$

Answer 1

The correct option is C $90mL$

6%(w/v) urea solution

$6$ g is present in 100 ml of water

$60$ g is present in 1000 ml of water or 1 litre

Molar mass of urea is $60$ g

That means 1 mole of urea is present in 1 litre of solution so molarity of urea solution is $1M$

$M_1=1M$

$M_2=0.1M$

$V_1=10mL$

$M_1{V}_1=M_2{V}_2$

$V_2=\frac{10}{0.1}=100$ mL

Volume added to make 100 mL solution$=100-10=90$ mL