A) \[-0.372{}^\circ C\]
B) \[-0.520{}^\circ C\]
C) \[+\text{ }0.372{}^\circ C~\]
D) \[-\text{ }0.570{}^\circ C\]
Correct Answer: A
Solution :
| [a] Depression in freezing point, |
| \[\Delta {{T}_{f}}={{k}_{f}}\times m\] |
| where, m = molality\[=\frac{{{w}_{B}}\times 1000}{{{M}_{B}}\cdot {{W}_{A}}}\] |
| \[=\frac{68.5\times 1000}{342\times 1000}=\frac{68.5}{342}\] |
| \[\Delta {{T}_{f}}=1.86\times \frac{68.5}{342}\] |
| \[=0.372{{\,}^{o}}C\] |
| \[\Delta {{T}_{f}}={{T}^{o}}-{{T}_{s}}\] |
| \[=0-{{0.372}^{o}}C\] |
| \[=-{{0.372}^{o}}C\] |
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