1A student determines the freezing point of a solution of 0.646 g of an unknown solid in 20.780 g of tertiary butyl alcohol (TBA). The freezing point of the solution (T_FP) is 22.7 ^oC. The freezing point of pure TBA (T_FP^o) is 24.5 ^oC. Note: The unknown solid does not dissociate.

Calculate T_FP , the freezing point depression. Report answer to proper sig figs and include the sign. Do NOT enter units.

2The molal freezing point depression constant, kf , is 8.09 oC/m for TBA(tertiary butyl alcohol). Calculate the molality (m) of the solution. Do not enter units. Do not use scientific notation.

3The units of molality (m) are moles of solute/kg of solvent. Calculate the moles of unknown solid in the solution. (Do not use scientific notation, do not enter units.)

4Calculate the molar mass (g/mol) of the unknown solid. Do not enter units, do not use scientific notation.