1. Tardigrade
  2. Question
  3. Chemistry
  4. Pure water freezes at 273 K and 1 bar. The addition of 34.5 g of ethanol to 500 g of water changes the freezing point of the solution. Use the freezing point depression constant of water as 2 K kg mol−1. The figures shown below represent plots of vapour pressure (V.P.) versus temperature (T). [molecular weight of ethanol is 46 g mol−1] Among the following, the option representing change in the freezing point is

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Q. Pure water freezes at $273 \,K$ and $1$ bar. The addition of $34.5\, g$ of ethanol to $500\, g$ of water changes the freezing point of the solution. Use the freezing point depression constant of water as $2\,K\, kg\,mol^{−1}$. The figures shown below represent plots of vapour pressure (V.P.) versus temperature (T). [molecular weight of ethanol is $46\, g\,mol^{−1}$]
Among the following, the option representing change in the freezing point is

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Solution:

$\Delta T _{ f }= K _{ f } \times m$
$=2 \times \frac{34.5 \times 2}{46}$
$=2 \times 1.5$
$=3$
Freezing point of ethanol $+$ water mixture
$=273-3=270$