Question

Calculate the molar mass of the unknown acid

A student knows or gathered the following information:

K_f = 5.12 °C/m

T_{f (pure)} = 35.7 °C

T_{f (solution)} = 44.4 °C

mass of solvent = 5.007 g

mass of unknown acid = 1.006 g

ΔT_f = m * K_f

_{Answer:________?}

Answer 1

Solution :

The depression in freezing point is given by ;

$\Delta T_{f} = K_{f}\times m$

Here, $\Delta$ T_f = T(pure solvent) - T(solution)

Note that the freezing points of solutions are all lower than that of the pure solvent. But, from the given data we can see that the freezing point of the pure solvent is less than that of the solution which is not possible for this condition.

So, this problem cannot be solved by this formula.