Question

An aqueous solution is prepared by diluting 3.30 mL of acetone (density = 0.789 g/mL) to get the final volume of 75 mL. Find the mole fraction of acetone. (Assume no volume change on mixing).

• A. 0.11
• B. 0.1
• C. 0.001
• D. 0.01

Answer 1

The correct option is D 0.01

We know that:
$Density=\frac{Mass}{Volume}$
$Massofacetone=volume\times density=3.30mL\times 0.789gm{L}^{-1}=2.603g$

Number of moles of acetone in the solution $=\frac{2.603g}{58gmo{l}^{-1}}=0.044mol$
$Massofwater=(Finalvolume–initialvolume)\times densityofwater$

We know that density of water is 1.00 g/mL

$Massofwater=(75.00mL-3.30mL)\times 1gm{L}^{-1}=71.70g$

Number of moles of water $=\frac{71.7}{18.0}=3.98mol$

We know that:
$Molefraction=\frac{numberofmolesofspecies}{totalnumberofmoles}$

$Molefractionofacetone=\frac{0.044}{0.044+3.98}=0.010$