From 10 kg of 20% solution, 400 g of salt was released on cooling. What is the mass fraction of the resulting solution?

Let’s find the mass of salt in the original solution:

m1 (salts) = mr.-pa1 (salts) * w1 (salts) / 100 = 10 * 20/100 = 2 (kg).

Find the mass of salt in the resulting solution:

m2 (salt) = m1 (salt) – mout. (salt) = 2 – 0.4 = 1.6 (kg).

Let’s find the mass of the resulting solution:

mr.-pa2 (salts) = m.-pa1 (salts) – mout. (salts) = 10 – 0.4 = 9.6 (kg).

Let’s find the mass fraction of salt in the resulting solution:

w2 (salts) = (m2 (salts) / mp.-pa2 (salts)) * 100 = (1.6 / 9.6) * 100 = 16.67 (%).