Question

Calculate the mass of oxalic acid (${\mathrm{H}}_2{\mathrm{C}}_2{\mathrm{O}}_4.2{\mathrm{H}}_2\mathrm{O}$) needed to prepare 250 ml,1 M aqueous solution of oxalic acid.

Answer 1

Molarity

• Molarity is defined as the number of moles of solute per volume of solution in liters.
• Molarity = $\frac{\mathrm{Number}\mathrm{of}\mathrm{moles}\mathrm{of}\mathrm{solute}}{\mathrm{Volume}\mathrm{of}\mathrm{solution}\mathrm{in}\mathrm{L}}$

Step 1: Determination of the molecular mass of Oxalic acid (${\mathrm{H}}_2{\mathrm{C}}_2{\mathrm{O}}_4.2{\mathrm{H}}_2\mathrm{O}$)
The molecular mass of oxalic acid = 126 g/mol

Step 2: Determination of the number of moles of Oxalic acid
Molarity = $\frac{\mathrm{Number}\mathrm{of}\mathrm{moles}\mathrm{of}\mathrm{solute}}{\mathrm{Volume}\mathrm{of}\mathrm{solution}\mathrm{in}\mathrm{L}}$
Number of moles of Oxalic acid = $\mathrm{Volume}\mathrm{of}\mathrm{solution}\times \mathrm{Molarity}$
Number of moles of Oxalic acid =0. 025 mol

Step 3: Determination of the mass of Oxalic acid
Number of moles = $\frac{\mathrm{Given}\mathrm{mass}}{\mathrm{Molar}\mathrm{mass}}$
Mass of Oxalic acid = $\mathrm{Molar}\mathrm{mass}\times \mathrm{Number}\mathrm{of}\mathrm{moles}$
Mass of Oxalic acid = $126\mathrm{g}/\mathrm{mol}\times 0.025\mathrm{mol}$
Mass of Oxalic acid = 3.15 g

Hence, the mass of Oxalic acid is 3.15 g.