Question

The equivalent weight of which of the following is the highest?

• A. $Na_2CO_3$ (molecular weight = 106)
• B. $H_3PO_4$ (molecular weight = 98)
• C. $H_2C_2O_4 \cdot 2H_2O$ (molecular weight = 126)
• D. $AlCl_3$ (molecular weight = 133.5)

Hint:

The n-factor for acids is the number of replaceable $H^+$ ions, for bases it's replaceable $OH^-$ ions, and for salts, it is the total magnitude of the positive or negative charge.

Answer 1

The Correct Option is C

1. $Na_2CO_3$: This salt dissociates into $2Na^+$ and $CO_3^{2-}$. Total positive/negative charge = 2. $$\text{Eq. Wt.} = \frac{106}{2} = 53$$

2. $H_3PO_4$: This is a tribasic acid. Basicity = 3. $$\text{Eq. Wt.} = \frac{98}{3} \approx 32.67$$

3. $H_2C_2O_4 \cdot 2H_2O$ (Oxalic Acid Dihydrate): This is a dibasic acid. Basicity = 2. $$\text{Eq. Wt.} = \frac{126}{2} = 63$$