When 551. mg of a certain molecular compound X are dissolved in 100 g of benzonitrile (CH, CN), the freezing point of the solution is measured to be 13.4 °C. Calculate the molar mass of X.

1.12g/mol

Explanation:

The freezing point depression of a solvent for the addition of a solute follows the equation:

ΔT = Kf*m*i

Where ΔT is change in temperature (Benzonitrile freezing point: -12.82°C; Freezing point solution: 13.4°C)

ΔT = 13.4°C - (-12.82) = 26.22°C

m is molality of the solution

Kf is freezing point depression constant of benzonitrile (5.35°Ckgmol⁻¹)

And i is Van't Hoff factor (1 for all solutes in benzonitrile)

Replacing:

26.22°C = 5.35°Ckgmol⁻¹*m*1

4.90mol/kg = molality of the compound X

As the mass of the solvent is 100g = 0.100kg:

4.9mol/kg * 0.100kg = 0.490moles

There are 0.490 moles of X in 551mg = 0.551g, the molar mass (Ratio of grams and moles) is:

0.551g / 0.490mol

= 1.12g/mol

This result has no sense but is the result by using the freezing point of the solution = 13.4°C. Has more sense a value of -13.4°C.

b. accuracy of the data matters alot more than its number of digits, organization or amount of detail. quantitative observation is more accepted than the qualitative observation.

water at room temperature is flowing through a pipe with pressure taps located 10 ft apart along one section of the pipe, which are connected to a mercury (s=13.6) manometer.