Question

25.0 g of barium hydroxide is dissolved in 120.0g of water. What is the morality?

Answer 1

Molarity: M = #moles of solute / liters of solution

# moles = mass / molar mass

Molar mass calculation

Barium hydroxide = Ba (OH)2

Atomic masses
Ba = 137.4 g/mol
O=16 g/mol
H=1 g/mol
Molar mass of Ba (OH)2 = 137.4 g/mol + 2*16g/mol + 2*1 g/mol = 171.4 g/mol

# mol = 25.0g/171.4 g/mol = 0.146 mol

For the volume of water use the fact that the density is 1g/ml., so 120 g = 120 ml = 0,120 liters.

M = 0.146mol / 0.120 liters = 1.22 mol/liter