QJEEM19Ch7c8d: JEE Main 2019 Chemistry - Class 11 JEEM19Ch7c8d Solution: 8 g of NaOH is dissolved in 18g of H 2 O. Mole fraction of NaOH …

Question

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8 g of NaOH is dissolved in 18g of H₂O. Mole fraction of NaOH in solution and molality (in mol kg^–1) of the solution respectively are -

Accepted Answer

8 gm of NaOH =

\frac{8}{40}

= 0.2 mol of NaOH

18 gm of H₂O =

\frac{18}{18}

= 1 mol of H₂O

∴

Total mole = 1 + 0.2 = 1.2 mol

∴

Mole fraction of NaOH =

\frac{0.2}{1.2}

= 0.167

We know,

Molality =

\frac{M o l e s o f s o l u t e}{W e i g h t o f s o l v e n t} \times

1000

=

\frac{0.2}{18} \times

1000

= 11.11

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