(a) Differentiate between molarity and molality for a solution. How does a change in temperature influence their values?
(b) Calculate the freezing point of an aqueous solution containing 10.50 g of MgBr2in 200 g of water. (Molar mass of MgBr2 = 184 g) (Kf for water = 1.86 K kg mol-1)
Molarity is defined as the number of moles of solute dissolved per liter of solution.
Molality of a solution is defined as the number of moles of solute dissolved in 1000 grams of solvent.
While molarity decreases with an increase in temperature, molality is independent of temperature. This happens because molality involves mass, which does not change with a change in temperature, while molarity involves volume, which is temperature dependent.
b) Given
w2 = 10.50 g
w1 = 200 g
Molar mass of MgBr2 (M2) = 184 g
Using the formula,
