Question

How much ethyl alcohol must be added to 1.00l of water so that the solution will not freeze at 1fahrenheit?

Answer 1

Answer:

Mass of ethyl alcohol needed will be: $=425.96g$

Explanation:

We know that :

1 Fahrenheit = -17.22 °C

The melting point of water is 0°C

In order to depress the freezing point to -17.22°C, we need to add some solute to water.

The amount of water given is 1 L = 1Kg

The relation between depression in freezing point and molality of a solution is

$\Delta T_{f}=k_{f}Xmolality\\where\\\Delta T_{f}=depressioninfreezingpoint=17.22\\k_{f}=cryoscopic constant of water=1.86^{0}C/m\\molality=\frac{moles}{mass(kg)}$

$17.22=1.86 Xmolality\\molality=9.26m$

$9.25=\frac{moles}{1}\\moles=9.26$

mass of ethyl alcohol needed will be:

$mass=moleXmolarmass=9.26X46=425.96g$