One litre hard water contains 12 mg Mg²⁺. Milli equivalents of washing soda required to remove its hardness is

Options

(a) 1
(b) 12.16
(c) 1 x 10⁻³
(d) 12.16 x 10⁻³

Correct Answer:

1

Explanation:

Equivalent weight of Mg2+ = molecular weight/ charge on ion
= 24/2 =12
Equivalent weight of Na2CO3 = Molecular Weight/ total charge =106/2 = 53
Weight of Mg2+ = 12mg =12/1000 gm
Let assume that Net weight of Na2CO3 required = w2
no.of equivalents of Mg2+ = no. of equivalent of Na2CO3 required
12/1000 * 12 = w2/53
w2 = 53/1000 gm
so milli equivalent of Na2CO3 required = (w2/E2) x 1000 = 1