for In the test you expected to show your work on the problems in order to get c

Question

for In the test you expected to show your work on the problems in order to get credit. Please be aware that problems requiring calculations, the answe shall result in zero (0) points rs given without the work shown will not be accepted and A 0.947g sample of an unknown solute dissolved in 15.0g of t-butanol produces a solution with a freezing point of 22.7 C. What is the molar mass of the solute? 1. For t-butanol, T-25.5 C; k-9.1 C.kg/mol. 2. Why should you wear goggles in the Lab at all times? How many grams of (NH,),SO, are required to prepare 240 g of 30% solution of this compound in water? 3. 4. In some solid calcium carbonate samples, calcium bicarbonate, Ca(HCO), is also present. Write a balanced equation for its reaction with hydrochloric acid. 5. In kinetic analysis of this experiment for the reaction of iodine ion with hydrogen peroxide, state the purpose for each of the following solutions.

Explanation / Answer

Solution

1)

Mass of solvent (t-butanol) = 15.0 g = 0.015 kg

We know that

?TF = KF · m · i, or

TF (Solvent) - TF (Solution) = KF · m · i

25.5 – 22.7 = 9.1 x (0.947/M x 0.015) x 1

2.8 = (574.51/M)

M = 574.51/2.8 = 205.18 g/mol

The molar mass of unknown solute = 205.18 g/mol (Ans.)

2)

The students are required to wear safety goggles having full side shields, in the lab at all time in order to provide safety to the eyes when anyone is actively working with chemicals in the laboratory.

3)

Solution of the compound is 30% i.e. for the preparation of 100 g solution, 30 g of ammonium sulphate is required.

Hence for the preparation of 240 g solution, the required of ammonium sulphate = (240 x 30) / 100 = 72 g (Ans.)

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