Question

One litre hard water contains 12 me Mg2+ ions. Milli equivalent of washing soda required to remove it's hardness is

a) 1

b12.26

c) 1*10^-3

d) 12.16*10^-3

Please sir/maam provide detailed explanation

Answer 1

A) 1
equivalent wt. of Mg2+ = molecular wt./ charge on ion
= 24/2 =12

equivalent wt. of Na2CO3 =molecular wt./ total charge on +ve or -ve ion

=106/2 = 53

weight of Mg2+ = 12mg =12/1000 gm

Net weight of Na2CO3 req. = w2

no.of equivalents of Mg2+ = no.of eq. of Na2CO3 req.
12/1000 * 12 = w2/53
w2 = 53/1000 gm

so milli eq. of Na2CO3 req. = (w2/E2) x 1000

=1