If 4 g of NaOH dissolves in 36 g of H2O, calculate the mole fraction of each component in the solution. Also, determine the molarity of solution (specific –1 gravity of solution is 1g mL ).
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Mass of NaOH = 4 g 4g Number of moles of NaOH = = 0.1 mol 40 g Mass of H2O = 36 g 36 g Number of moles of H2 O = = 2 mol 18 g Number of moles of H2 O Mole fraction of water = No. of moles of water + No. of moles of NaOH 2 2 = = = 0.95 2 + 0.1 2.1 Number of moles of NaOH Mole fraction of NaOH = No. of moles of NaOH + No. of moles of water 0.1 0.1 = = = 0.047 2 + 0.1 2.1 Mass of solution = mass of water + mass of NaOH = 36 g + 4 g = 40 g Volume of solution = 40 × 1 = 40 mL –1 (Since specific gravity of solution is = 1 g mL ) Number of moles of solute Molarity of solution = Volume of solution in litre 0.1 mol NaOH = = 2.5 M 0.04 L