To 120 g of a 60% ethanol solution, 40 g of anhydrous ethanol was added. Calculate the mass fraction

To 120 g of a 60% ethanol solution, 40 g of anhydrous ethanol was added. Calculate the mass fraction of ethyl alcohol in the resulting solution.

Given:

m (solution) = 120 g

m (C2H5OH) = 40 g

w% (C2H5OH) = 60%

To find:

w% (C2H5OH in the final solution) -?

Decision:

1) Find the mass of alcohol in the primary solution:

m (C2H5OH) = 120 g * 0.6 = 72 g;

2) Find the mass of alcohol after adding a portion:

m (C2H5OH) = 72 g + 40 g = 112 g;

3) Find the mass of the solution after adding alcohol:

m (solution) = 120 g + 40 g = 160 g;

4) Find the mass fraction of alcohol in the solution:

w% (C2H5OH) = m (C2H5OH): m (solution) * 100% = 112 g: 160 g * 100% = 70%.

Answer: w% (C2H5OH) = 70%.