Question

An aqueous solution is 1.00% by mass ethanol, CH3CH2OH, and has a density of 0.996 g/mL.

Answer 1

The molarity of ethanol in the solution is 0.217 M

Further explanation

Given

1% by mass

density = 0.996 g/ml

Required

The molarity

Solution

mass/ml of Ethanol :

1% x 0.996 g/ml = 0.00996 g/ml

For 1 L solution :

0.00996 g/ml x 1000 ml/L = 9.96 g/L

Convert to mol/L(MW ethanol=46 g/mol) :

9.96 g/L : 46 g/mol= 0.217 mol/L = 0.217 M

Or you can use equation :

$\tt M=\dfrac{\%mass\times \rho\times 10}{MW}\\\\M=\dfrac{1\times 0.996\times 10}{46}=0.217$