Question

Determine the molarity of a solution of potassium chloride that is prepared by dissolving 1.4753 g of KCl in a 100-mL volumetric flask and filling it to the calibration mark with deionized water. Use a molar mass with at least 4 significant figures so that the number of SF in the calculated molarity is not limited. Show all calculations (including labeled conversion factors) and express the answer with the appropriate number of significant figures. According to the manufacturer, the volume of a 100-mL volumetric flask is 100.00 + 0.08 mL.

Answer 1

Molarity = number of moles of solute / Volume of solution in litre

Number of moles = Mass in gram / Molar mass

Mass of KCl = 1.4753 g, Molar mass of KCl = 74.5513 g/mol

Number of moles of KCl = 1.4753 g / 74.5513 g/mol = 0.01979 mol

Volume of solution = 100 ml = 100 L / 1000 = 0.100 L

Molarity = 0.01979 mol / 0.100 L = 0.1979 mol/L = 0.1979 M