The density of 3M solution of NaCL is 1.25 g/mL. Calculate molality of the solution

Asked by Shippyupadhyay2304 | 18th Jul, 2018, 10:28: PM

Expert Answer:

Given:
 
Density of solution = 1.25 g/mL
 
M =3 mol/lit

 
Molar space mass space of space NaCl space equals space 58.5 space

we space know space that comma

No. space of space moles space equals fraction numerator Weight space over denominator Molecular space weight end fraction

Weight space equals No. space of space moles cross times Molecular space weight


therefore Mass space of space NaCl space in space 1 space litre space solution space equals space 3 cross times 58.5 space

space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space equals 175.5 space straight g

Density space equals Mass over Volume

Mass space equals space Density cross times Volume

therefore space Mass space of space 1 space litre space solution space equals space 1000 cross times 1.25

space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space equals 1250 space straight g

Mass space of space water space in space solution space equals space Mass space of space solution space minus Mass space of space solute

space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space equals 1250 minus 175.5

space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space equals 1074.5 space straight g

Mass space of space water space in space solution space equals space 1.074 space kg


Molality space equals fraction numerator No. space of space moles space of space solute over denominator Mass space of space solvent space in space kg end fraction

space space space space space space space space space space space space space equals fraction numerator 3 over denominator 1.074 end fraction

Molality space equals 2.79 space straight m
 
Molality of the solution is 2.79 m.

Answered by Varsha | 19th Jul, 2018, 11:17: AM