A 9.38 gram sample of a compound is dissolved in 250.0 grams of benzene. The freezing point of this solution is 1.02 ˚C below that of pure benzene. What is the molar mass of this compound? Kf for benzene is 5.12 ˚C/m and you may assume i = 1.

THE MOLAR MASS OF THE COMPOUND IS 45.31 G/MOL.

Explanation:

Using the formula;

          Change in freezing point Δt = i Kf m

where;

i = Van Hoff constant = 1

Kf = freezing point dissociation constant = 5.12 °C /m

M = molarity = unknown

The freezing point of benzene = 5.444°C

Temperature of the final solution = 1.02°C

First is to calculate the change in the temperature

= Temperature of benzene - temperature of the solution

=  5.444 - 1.02

= 4.424 °C

Next is the use the above formula to solve for the molarity

Δt = i Kf m

4.244 = 1 * 5.12 * m / 0.250 kg of benzene

We have to divide the molarity by the mass of benzene used since it was not 1 kg if benzene that was used.

So therefore,

4.244 = 20.48 * m

m = 4.244 / 20.48

m = 0.207 mol.

Next is to calculate the molar mass of the compound:

             Molarity = mass / molar mass

Molar mass = mass/ molarity

Molar mass = 9.38 g / 0.207 mol

Molar mass = 45.31 g /mol

The molar mass of the compound is 45.31 g/mol.

most historians agree that gabriel mouton, the vicar of st. paul’s church in lyons, france, is the “founding father” of the metric system. he proposed a decimal system of measurement in 1670. mouton based it on the length of one minute of arc of a great circle of the earth (now called a nautical mile, 1852 meters). he also proposed the swing-length of a pendulum with a frequency of one beat per second as the unit of length (about 25 cm). a pendulum beating with this length would have been fairly easy to produce, thus facilitating the widespread distribution of uniform standards. over the years, his work was revised, improved, and extended by a number of french scientists.

the political sponsor of weights and measures reform in the french revolutionary national assembly was the bishop of autun, better known as talleyrand. under his auspices, the french academy appointed several committees to carry out the work of developing a usable system of weights and measures for france. one of the committees recommended a decimalized measurement system based upon a length equal to one ten-millionth of the length of a quadrant of the earth’s meridian (i.e., one ten-millionth of the distance between the equator and the north pole).