KVPY 2020-21 SB SX Exam Previous Papers

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Question : 49 of 120

Marks: +1, -0

The boiling point (in

{ }°{C}

) of

0.1

molal aqueoussolution of

{CuSO}_{4} .5 {H}_{2} {O}

at 1 bar is closest to:
[Given: Ebullioscopic (molal boiling point elevation)constant of water,

{K}_{{b}}=0.512 {\K} {\Kg} {\mol}^{-1}]:-

100.36
99.64
100.10
99.90

Solution:

{CuSO}_{4} .5 {H}_{2} {O}\;{────▶}↖{H_2O}{Cu}^{2 \⊕ }+{SO}_{4}^{2 \⊖ }

i = 2

\Δ{T}_{{b}}={i} \.{K}_{{b}} \.{m}=2 \×0.512 \×0.1

=0.1024

{T}_{{b}}'={T}_{{b}}^{0}+\Δ{T}_{{b}}

=100+0.1024=100.10

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