Question

You are given two samples of HCl with molarity 0.341 and 0.143; volume of each sample being 1 litre. What will be the maximum volume of 0.243 M HCl that can be obtained by mixing the given samples in the following two conditions?
(i) When water is added for dilution.
(ii) When no water is added.

Answer 1

Ans. (i) 2.0204 litre; (ii) 1.98 litre
(i) Let x litre of 0.341 M HCl and 1 litre of 0.143 M HCl be mixed to obtain 0.243 M HCl.
$M_1{V}_1+M_2{V}_2=M_R(V_1+V_2)$
$0.341\times x+0.143\times 1=0.243(1+x)$
$(0.341-0.243)x=0.243-0.143$
$0.098x=0.1$
$x=1.0204litre$
Total volume $=1+x=2.0204litre$
Since, volume is greater than 1 litre, hence water is to be added.
(ii) Let x litre of 0.143 M HCl and 1 litre of 0.341 M HCl are mixed to obtain 0.243 M HCl.
$M_1{V}_1+M_2{V}_2=M_R(V_1+V_2)$
$0.143\times x+0.341\times 1=0.243(1+x)$
$0.1x=0.098$
$x=0.98litre$
Total volume $=1+x=1.98litre$
Since, volume is less than two litre, no water is to be added.