Question

1. If you place 10.0 L of heptane (CHio) in a sealed room that is 5.25 m long, 2 m wide, and 2.75 m igh, will all the heptane evaporate? If some liquid remains, how much will there be? The vapor pressure of heptane is 13.9 torr at 25 °C, and the density of the liquid at this temperature is 0.684 g/mL. Treat the room dimensions as exact numbers.

Answer 1

Volume of liquid heptane
10.0 L × 1000 mL/L-10000 mL

Density is 0.684 g/mL.
Mass of liquid heptane
10000 mL × 0.684 g/mL-68401

Molar mass of heptane

C7H16 7(12) 16(1) 8416 100 g/mol

Number of moles of liquid heptane

6840 g 8. mol 100 g/mol

Volume or room

V = 5.25 m × 2 m × 2.75 m V = 28.875 m3 V = 28.875 ㎡ × 1000 L "> 7m V- 28875 L

Temperature
T = 25 °C, (25 + 273) K-298 K

Vapour pressure
P 13.9 torr x 0.01789 atm 760 torr

The ideal gas constant
L·atm mol K R- 0.08206

The number of moles of heptane in vapour phase

0.01789 atm × 28875 L rl 0.08206 77201 cdot K × 298K

n 21.13 mol

Thus, out of 68.4 moles of liquid heptane, 21.13 moles will evaporate and come into vapour phase.

will remain in liquid phase

68.4-21.13-47.27 moles

Molar mass of heptane

C7H16 7(12) 16(1) 8416 100 g/mol

Mass of liquid heptane remaining

47.27 mol × 100 g/mol 4727 g

Density is 0.684 g/mL.

Volume of liquid heptane remaining

4727 g -6911 mL 0.684 g/mL

Convert volume from mL to L

6911 ml_ 6.91 L 1000 mL/L mL -6.91 L

Hence, all of heptane will not evaporate and 6.91 L liquid heptane will remain.