Question

Please help with these two

1. A flask is filled with 1.08 moles of a gas at 20.7 K and 646.8 mm Hg. The flask is then opened and an additional 1.33 moles are added. The temperature of the flask is then changed to 272.4 K. What is the pressure (in atm) of the flask under these final conditions?

2. The density of a gas is 4.22 g/L at a pressure of 1.77 atm and a temperature of  14.66 °C. What is the molar mass (in g/mol) of the gas?

QUESTION 3 A flask is filled with 1.08 moles of a gas at 20.7 K and 646.8 mm Hg. The flask is then opened and an additional 1.33 moles are added. The temperature of the flask is then changed to 272.4 K. What is the pressure (in atm) of the flask under these final conditions? QUESTION 4 The density of a gas is 4.22 g/L at a pressure of 1.77 atm and a temperature of 14.66 °C. What is the molar mass (in g/mol) of the gas?

Answer 1

3)

Given:

Pi = 646.8 mmHg

ni = 1.08 mol

nf = 1.08 + 1.33 = 2.41 mol

Ti = 20.7 K

Tf = 272.4 K

use:

(Pi*Vi)/(ni*Ti) = (Pf*Vf)/(nf*Tf)

(646.8 mmHg)/(1.08 mol*20.7 K) = (Pf)/(2.41 mol*272.4 K)

Pf = 18993 mmHg

= 18993 / 760 atm

= 25.0 atm

Answer: 25.0 atm

B)

P = 1.77 atm

T= 14.66 oC

= (14.66+273.15) K

= 287.81 K

density = 4.22 g/L

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:

1.77 atm * MM = 4.22g/L * 0.08206 atm.L/mol.K *287.81 K

MM = 56.28 g/mol

Answer: 56.28 g/mol