The elevation of boiling point of 0.10 m
aqueous CrCl3.xNH3 solution is two times that
of 0.05 m aqueous CaCl2 solution. The value of
x is ______.
[Assume 100% ionisation of the complex and
CaCl2, coordination number of Cr as 6, and that
all NH3 molecules are present inside the
coordination sphere]
Answer (integer)
5
Solution
Molality of CaCl<sub>2</sub> solution = 0.05 m
<br><br>$\Delta$T<sub>b</sub> = i K<sub>b</sub> m = 3 × K<sub>b</sub> × 0.05 = 0.15 K<sub>b</sub>
<br><br>Molality of CrCl<sub>3</sub>.xNH<sub>3</sub> = 0.10 m
<br><br>$\Delta$T<sub>b</sub><sup>'</sup> = i K<sub>b</sub> $\times$ 0.10
<br><br>Given, $\Delta$T<sub>b</sub><sup>'</sup> = 2$\Delta$T<sub>b</sub>
<br><br>$\Rightarrow$ i K<sub>b</sub> $\times$ 0.10 = 0.15 K<sub>b</sub>
<br><br>$\Rightarrow$ i = 3
<br><br>Co-ordination number of Cr is 6.
<br><br>[Cr(NH<sub>3</sub>
)<sub>x</sub>.Cl<sub>6-x</sub>]Cl<sub>3-6+x</sub> $\to$ [Cr(NH<sub>3</sub>
)<sub>x</sub>Cl] + (3-6+x)Cl<sup>–</sup>
<br><br> i = 3 = 1 + 3 - 6 + x
<br><br>$\Rightarrow$ x = 5
About this question
Subject: Chemistry · Chapter: States of Matter · Topic: Gas Laws
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