Using the reaction equation Fe (OH) 2 = FeO + H2O, determine the mass of iron (II)

Using the reaction equation Fe (OH) 2 = FeO + H2O, determine the mass of iron (II) oxide formed during the decomposition of 45 g of the starting material.

Given:
m (Fe (OH) 2) = 45 g
To find:
m (FeO) =?
Decision:
1) Let’s compose the equation of the chemical reaction, let the iron oxide be x g.
Fe (OH) 2 = FeO + H2O
2) Find the molecular weights of iron hydroxide and iron oxide.
M (Fe (OH) 2) = 56 + 32 + 2 = 90 g / mol
M (FeO) = 56 + 16 = 72 g / mol
3) 45 g: 90 g / mol = x: 72 g / mol
x = (45 x 72): 90 = 36 g.
Answer: m (FeO) = 36 g.