Determine the mass of magnesium nitrate obtained by the interaction of 20 grams of magnesium oxide with nitric acid.

Let’s find the amount of MgO by the formula:

n = m: M.

M (MgO) = 40 g / mol.

n = 20 g: 40 g / mol = 0.5 mol.

Let’s compose the reaction equation, find the quantitative ratios of substances.

MgO + 2HNO3 = Mg (NO3) 2 + H2O.

For 1 mole of MgO, there is 1 mole of Mg (NO3) 2. Substances are in quantitative ratios 1: 1.

n (MgO) = n (Mg (NO3) 2) = 0.5 mol

Find the mass of Mg (NO3) 2:

m = n × M,

M (Mg (NO3) 2) = 148 g / mol.

m = 0.5 mol × 148 g / mol = 74 g.

Answer: 74 g.