Question

8. If molality of chloroform (CHCI3) in benzene (C6H6) is
5.18, then mole fraction of chloroform in the solution
is
(1) 0.15
(2) 0.29
(3) 0.42
(4) 0.51​

Answer 1

answer : option (2) 0.29

explanation : molar mass of chloroform = 12 + 1 + 35.5 × 3 = 119.5 g/mol

molar mass of benzene = 78 g/mol

given, molality of chloroform is 5.18m. it means, 5.18 moles of chloroform included in 1kg of benzene.

so, mole of benzene = mass of benzene/molar mass of benzene = 1kg/78g/mol = 1000g/78g/mol = 12.82 mol

so, mole fraction of chloroform = mole of chloroform/(mole of chloroform + mole of benzene)

= 5.18/(5.18 + 12.82)

= 5.18/18

= 2877 ≈ 0.29

hence, option (2) is correct choice.

Answer 2

Hey Dear,

◆ Answer -

(2) 0.29

● Explanation -

Molality of the solution is given by -

Molality = moles of solute / mass of solvent

5.18 m solution means 5.18 moles of CHCl3 is dissolved in 1 kg of C6H6.

Moles of benzene are calculated as -

Moles (C6H6) = given weight / molar mass

n1 = 1000 / 78

n1 = 12.82 mol

Mole fraction of chloroform in solution is calculated by -

X2 = n2 / (n1 + n2)

X2 = 5.18 / (12.82 + 5.18)

X2 = 5.18 / 18

X2 = 0.2878

Therefore, mole fraction of CHCl3 in C6H6 solution is 0.2878 .

Thanks for asking...