What amount of calcium nitrate substance is needed to prepare 820 grams of a solution with a mass fraction of 4%?

We find the mass of a substance by multiplying its mass fraction by the mass of the solution.

M salt = 820 x 0.04 = 32.8 grams;

Let’s find the molar mass of the salt.

M Ca (NO3) 2 = 40 + (14 + 16 x 3) x 2 = 164 grams / mol;

Let us find the amount of the salt substance by dividing its mass by the molar mass.

N Ca (NO3) 2 = 32.8 / 164 = 0.2 mol;