How do u calculate Molality?

Question

Calculate the molality, new boiling point, and new freezing point of a solution that is prepared by adding 25 grams of glucose (GMM = 180) to 100mL of water.

Answer 1

Molality is moles of solute / kg of solvent. For water, it's important to remember that 1 mL of water weighs 1g.

Moles of solute = 25 g / 180 g/mol = .1389 moles
kg of solvent: 100 mL = 100 g = .1 kg

Molality = moles / kg of solvent = .1389 moles / .1 kg = 1.389 molal (solution!)