Question

$150$ mL of $C_2{H}_{5}OH$ (density $=0.78gm{L}^{-1}$) is diluted to one litre by adding water; molarity of the solution is:

• A. $2.54$
• B. $11.7$
• C. $2.99$
• D. $29.9$

Answer 1

Answer: (A)

$2.54$

Mol. Wt. of $C_2{H}_{5}OH$ $=2\times 12+5\times 1+16+1=46$

Volume of $C_2{H}_{5}OH=150ml$

Density $=0.78g/mL$

$\therefore$ Mass of $C_2{H}_{5}OH$$=0.78\times 150=117g$

Moles of $C_2{H}_{5}OH$ $=\frac{117}{46}=2.54$

The final volume of a solution made up to $=1L$

Molarity $=\frac{\text{No. of moles of solute}}{\text{Volume of solution (in L)}}$

$=\frac{2.54}{1}=2.54$