Determine the mass of the solution if its concentration = 35% and the solute in it is 40 grams.

Explanation of the solution to the problem: the mass fraction of the solute is found by the formula:
w = m (r.v.) / m (r-ra) * 100%, where w is the mass fraction, m (r.v.) is the mass of the solute, m (r-ra) is the mass of the solution. Consequently, the mass of the solution is calculated by the formula: m (solution) = m (r.v.) / w, where w is expressed in fractions. Substituting the data from the condition, we get: m (solution) = m (r.v.) / W = 40 / 0.35 = 114.29 g.