Find the mass of slaked lime that is formed by the interaction of calcium oxide weighing 28 g with water.

Given:
m (CaO) = 28 g
To find:
m (Ca (OH) 2) =?
Decision:
1) Let’s compose the equation of the chemical reaction, let the mass of slaked lime be x g.
CaO + H2O = Ca (OH) 2
2) Find the molecular weights of calcium oxide and hydroxide.
M (CaO) = 40 + 16 = 56 g / mol
M (Ca (OH) 2) = 40 + (16 x 2) + (1 x 2) = 74 g / mol
3) 28 g: 56 g / mol = x g: 74 g / mol
x = (28 x 74): 56 = 37 g / mol
Answer: m (Ca (OH) 2) = 37 g / mol.