Molality
NEED Formulas:
Molality = (moles of solute) / (kg of solvent)
Density = Mass / Volume
Practice Problems: (Some might have 2 parts)
1. 7.45 g of Potassium chloride (KCl) was dissolved in 100 g of
water. Calculate the molality of the solution. (1 Question)
2. 11.11 g of Urea (NH2CONH2) was dissolved in 100 g of water.
Calculate the molarity and molality of the solution.
(2 Questions)
a. GIVEN: N = 14 g/mol, H = 1 g/mol, C = 12 g/mol, and
O = 16 g/mol
3. 34.2 g of sugar was dissolved in water to produce 214.2 g of
sugar syrup. Calculate molality of the solution. (1 Question)
a. GIVEN: C = 12 g/mol, H = 1 g/mol, and O = 16 g/mol
4. 10 g KCl is dissolved in 1000mL of water. If the density of
water is 1 g/cm3 calculate the molarity and molality.
(2 Questions)
a. GIVEN: K = 39 g/mol and Cl = 35.5 g/mol
b. NEEDED CONVERSION: 1 mL = 1 cm3
5. Calculate the molarity and molality of the sulphuric acid
solution of density 1.198 g/cm3 containing 27% by mass of
sulphuric acid. (2 Questions)
a. GIVEN: Sulphuric acid molecular weight is 98 g/mol
b. ASSUME: 100g for the solution, 1% = 1 g