Question

What amount of Na2co3, is dissolved in 250 ml water
to prepare semimolar solution?
(1) 2.65 g
(2)3.71 g
(3) 13.25 g
(4)0.90 g​

Answer 1

Answer: To prepare a semimolar solution, we need 13.25g Na2CO3.

STEP BY STEP EXPLANATION

We know,

Molecular weight of Na2CO3= (23×2)+12+(16×3)= 106

To get a molar solution from 1000ml water, we need 106g Na2CO3

So, to get a molar solution from 250ml water, we need= (106×250)/1000= 26.5g Na2CO3

A semimolar solution is denoted by 0.5 molar solution.

So, to get a semimolar solution, we need= 26.5×0.5= 13.25g Na2CO3