MCQ
  Column $-I$ (various
solutions)
  Column $-II$
(Their freezing
point )
$a$ $0.1\,M$ $BaCl_2$ solution $p$ $271\,K$
$b$ $0.1\,M$ $NaCl$ solution $q$ $270\,K$
$c$ $0.1\,M\, K_3 [Fe(CN)_6]$ solution $r$ $268\,K$
$d$ $0.1\,M\, Al_2 (SO_4)_3$ solution $s$ $269\,K$

Given : Freezing point of $0.1\,M$ sucrose solution $= 272\,K$ and $F.pt.$ of water $= 273\,K$ 

Which of the following option show correct matches ?

  • A
    $(a-r), (b-p), (c-s), (d-q)$
  • $(a-q), (b-p), (c-s), (d-r)$
  • C
    $(a-q), (b-s), (c-p), (d-r)$
  • D
    $(a-s), (b-q), (c-r), (d-q)$

Answer

Correct option: B.
$(a-q), (b-p), (c-s), (d-r)$
b
$\mathrm{i}=1+\left(\frac{1}{\mathrm{n}}-1\right) \alpha$

$\mathrm{i}=1+\left(\frac{1}{3}-1\right) \times 0.8=0.47$

$\Delta \mathrm{T}_{\mathrm{f}}=\mathrm{i} \mathrm{K}_{\mathrm{f}}$ molality

${=0.47 \times 5.12 \times 0.25} $

$=\,0.6{{\,}^{o}}C$

$\Delta \mathrm{T}_{\mathrm{f}}=\mathrm{T}_{\mathrm{o}}-\mathrm{T}_{\mathrm{s}}$

$0.6=5.5-\mathrm{T}_{\mathrm{s}}$

$\mathrm{T}_{\mathrm{s}}=4.9\,^{o} \mathrm{C}$ or $278\, \mathrm{K}$

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