Magnesium oxide was treated with 60 g of a solution containing 20% nitric acid. What is the mass of the salt?

To solve this problem, we write down the given: m (solution) = 60 g w (HNO3) = 20% or 0.2
Find: m (salt) -?
Solution:
Let’s write down the reaction equation.
MgO + HNO3 = Mg (NO3) 2 + H2O
Let’s arrange the coefficients:
MgO + 2HNO3 = Mg (NO3) 2 + H2O
Let’s calculate the mass of nitric acid that has reacted.
Let’s write down the formula for the calculation.
w = m (substance) / m (solution)
m (substance) = w * m (solution)
m (substance) = 0.2 * 60 = 12 g
Let’s calculate the molar masses of nitric acid and magnesium nitrate.
M (HNO3) = 1 + 14 + 16 * 3 = 63 g / mol
M (Mg (NO3) 2) = 24 + (14 + 16 * 3) * 2 = 148 g / mol
Above magnesium nitrate we write x g, under – 148 g.
We write 12 g over nitric acid, 126 g underneath.
Let’s compose and solve the proportion:
x = 12 * 148/126 = 14.1 g
Answer: 14.1 g