Question

1. A mixture of four alkenes (1-decene, 1-heptene, 1-nonene, and 1-octene) was analyzed by gas chromatography. Below, on the line, list the four alkenes in order of increasing retention time: 2. At 760.0 mm atmospheric pressure, a binary liquid mixture of components A and B gives the temperature composition diagram shown below. The liquid curve plots boiling point vs. composition of the liquid mixture. The vapor curve plots temperature vs. equilibrium vapor composition. A horizontal line on the diagram, such as L4V4, joins the composition of the boiling liquid mixture with the corresponding vapor composition above the liquid at equilibrium at the same temperature. To two significant figures: a. What is the boiling point of the liquid mixture of 20.0% A plus 80.0% B? b. What is the composition of the vapor over the liquid mixture of 20.0% A plus 80.0% B? percentage of A percentage of B_ c. If the vapor referred to in question 2b is condensed and the resulting liquid is heated, what is the composition of the vapor over this liquid at its boiling point? percentage of A percentage of B d. If the vapor referred to in question 2c is condensed and the resulting liquid is heated, what is the boiling point of this liquid? Vi bpb Vapor Liquid Temperature - L3 100% A 0% 80 20 60 40 40 60 20 80 0% 100% B 3. Are the following statements about gas chromatography true or false? [Write T for true, F for False.) a. On an achiral column, two enantiomers have the same retention time and cannot be separated. b. Increasing the carrier gas flow rate will decrease the retention time of a volatile compound. _c. Increasing the temperature of the column will decrease the retention time of a volatile compound. 4. Dalton's law states that the mole fraction of cyclohexane in the vapor at a given temperature is equal to the partial pressure of the cyclohexane at that temperature divided by the total pressure. In the vapor in equilibrium with a mixture of 50.0% methylcyclohexane and 50.0 % cyclohexane at 363K, cyclohexane has a partial pressure of 482.2 mm and methylcyclohexane has a partial pressure of 269.7 mm. The atmospheric pressure is 751.9 mm, so the liquid boils. If some of the vapor in equilibrium with the boiling mixture were condensed and analyzed quantitatively by gas chromatography, what would be the mole percent of methylcyclohexane? (A numerical answer is required, accurate to three significant figures.)

Answer 1

1- 1-decene>1-nonene>1-octene>1-heptene

2- a) 80, b) A-50, B-50, c) A-80, B-20, d) 50

3- a) False, b) True, c) True

4- Mole fraction of methylcyclohexane= 269.7/751.9 = 0.359