Question

What weight of H2C2O4 . 2H2O (mol. wt. = 126) should be dissolved to prepare 250 ml of centinormal to be used as a reducing agent?

(A) 0.63 gm

(B) 0.1575 gm

(C) 0.126 gm

(D) 0.875 gm

Answer 1

Correct Answer is: (B) 0.1575 gm

Per mole of given acid C2O42– present = 1 mole

∴ C2O4 2– → CO2 + 2e

∴ x factor for H2C2O4 . 2H2O as a reducing agent = 2

∴ equiv. wt. = 126/2 = 63

250 ml of centinormal solution

= 250/100 x 10-3 equiv.

wt. of H2C2O4 . 2H2O required

= 250/100 x 10-3 × 63 gm = 0.1575 gm