Use the vapour pressures (at 25 °C) of the pure substances below to answer the f

Question

Use the vapour pressures (at 25 °C) of the pure substances below to answer the following questions.

1. Determine the partial pressure (in kPa) of 1,4-pentadiene (C5H8) in the vapour phase (at 25 °C) over a solution for which the mole fraction of 2-methyltetrahydrofuran (C5H10O) is 0.564. Report your answer to three significant figures in scientific notation.

2. A solution of 2-methyltetrahydrofuran (C5H10O) and 1,4-pentadiene (C5H8) is prepared by adding 1.11 g of 2-methyltetrahydrofuran to 1.1 g of 1,4-pentadiene. Determine the mole fraction of 2-methyltetrahydrofuran in the vapor phase (at 25 °C). Report your answer to three significant figures in scientific notation.

Explanation / Answer

1. partial pressure of 1,4-pentadiene(p) = x*p0

x = molefraction of 1,4-pentadiene = 0.564

p0 = vapor pressure of pure 1,4-pentadiene = 97.9 kpa

p = 0.564*97.9 = 55.2 kpa

2.

No of mol of 2-methyltetrahydrofuran taken(n1) = w/Mwt = 1.11/86.134

                                            = 0.0129 mol
No of mol of 1,4-pentadiene(n2) = 1.1/68.12

                             = 0.016 mol

molefraction of 2-methyltetrahydrofuran = n1/n1+n2

                 = (0.0129/(0.0129+0.016))

                 = 0.446

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