The Molarity (M) of an aqueous solution containing 5.85 g of NaCl in 500 mL water is : (Given : Molar Mass Na: 23 and Cl: 35.5 gmol⁻¹)

Solution

Chemistry ma’am · 3 steps

Turn grams into moles first, millilitres into litres second, then divide.

1. Moles of NaCl. Molar mass of NaCl is 23 + 35.5 = 58.5 g mol⁻¹. So moles = 5.85/58.5 = 0.1 mol.
2. Volume in litres. Molarity needs litres: 500 mL = 0.5 L. The solution is dilute, so its volume is taken as the 500 mL of water.

   M = n/(V (L)) = (0.1 mol)/(0.5 L) = 0.2 mol L⁻¹

3. So. The molarity is 0.2 M, option (d).

The idea to keep. Molarity is moles of solute per litre of solution. A quick shortcut is M = w/Mₘₒₗₐᵣ × 1000/(V (mL)).

Answer from the NTA final answer key. Solution by PrepWiser.