Question

Equal moles of H20 and NaCl are present in a solution. Hence, molality of NaCl solution is:
(A) 0.55
(C) 1.00
(B) 55.5
(D) 0.18​

Answer 1

Let the no. of moles of both the compounds be x,

Now,
molarity= no. of moles/ volume (litre).

So we need to find volume here only since we already have no. of moles of NaCl as x.

Now,
Using density relation for water (since it's the solvent here),

mass/ volume = 1000kg/m^3

molar mass×no. of moles/ volume = 1000kg/m^3

18x/ volume = 1000kg/m^3

Volume = 18x/1000,

susbtituing this value in molarity part,


we have,

molarity=
$\frac{x}{ \frac{18x}{1000} } \\ \\ = \frac{1000x}{18x} \\ \\ = \frac{500}{9} \\ \\ = 55.55 \: M$



Hence option (B) is the answer.