Question

Be sure to answer all parts. The air in a hot-air balloon at 785 torr is heated from 15.0°C to 41.0°C. Assuming that the moles of air and the pressure remain constant, what is the density of the air at each temperature? (The average molar mass of air is 29.0 g/mol.)

Density at 15.0°C g/L?

Density at 41.0°C g/L?

Answer 1

1)

P= 785.0 torr

= (785.0/760) atm

= 1.0329 atm

T= 15.0 oC

= (15.0+273) K

= 288 K

Lets derive the equation to be used

use:

p*V=n*R*T

p*V=(mass/molar mass)*R*T

p*molar mass=(mass/V)*R*T

p*molar mass=density*R*T

Put Values:

1.0328947368421053 atm *29.0 g/mol = density * 0.08206 atm.L/mol.K *288.0 K

density = 1.2674 g/L

Answer: 1.27 g/L

2)

T= 41.0 oC

= (41.0+273) K

= 314 K

USE:

p*molar mass=density*R*T

Put Values:

1.0328947368421053 atm *29.0 g/mol = density * 0.08206 atm.L/mol.K *314.0 K

density = 1.16 g/L

Answer: 1.16 g/L