Question

Calculate the number of molecules of oxalic acid \((\text{H}_2\text{C}_2\text{O}_4\cdot2\text{H}_2\text{O})\) in 100 mL of 0.2 N oxalic acid solution.

Hint:

For acids and bases, convert normality to moles using the number of replaceable hydrogen ions before calculating molecules.

Answer 1

Step 1: Normality (\(N\)) is defined as: \[ N = \frac{\text{gram equivalents}}{\text{litre of solution}} \] Given: \[ N = 0.2,\quad \text{Volume} = 100\,\text{mL} = 0.1\,\text{L} \]
Step 2: Calculate the number of gram equivalents: \[ \text{Gram equivalents} = N \times V = 0.2 \times 0.1 = 0.02 \]
Step 3: Oxalic acid is a dibasic acid, so: \[ 1 \text{ mole of oxalic acid} = 2 \text{ equivalents} \]
Step 4: Calculate number of moles of oxalic acid: \[ \text{Moles} = \frac{0.02}{2} = 0.01 \]
Step 5: Calculate the number of molecules: \[ \text{Number of molecules} = 0.01 \times 6.022 \times 10^{23} \] \[ = 6.022 \times 10^{21} \]