Question

Gasses

a) What is the molar mass of a gas if 5.50 g of the gas fills a 50.0 L container with a pressure of 1590 torr at 30°C?

b) 100.0 g of calcium carbonate (CaCO₃ ) in a 25.0 L container is heated to 600°C, producing calcium oxide (CaO) and carbon dioxide (CO₂).

What is the pressure generated in the container when all of the CaCO₃ is consumed? after it is allowed to cool down to 20°C?

CaCO₃ (s) --> CaO (s) + CO₂ (g)

Answer 1

a)

Given:

P = 1590.0 torr

= (1590.0/760) atm

= 2.0921 atm

V = 50.0 L

T = 30.0 oC

= (30.0+273) K

= 303 K

find number of moles using:

P * V = n*R*T

2.0921 atm * 50 L = n * 0.08206 atm.L/mol.K * 303 K

n = 4.207 mol

mass(solute)= 5.50 g

use:

number of mol = mass / molar mass

4.207 mol = (5.5 g)/molar mass

molar mass = 1.307 g/mol

Answer: 1.31 g/mol

b)

Molar mass of CaCO3,

MM = 1*MM(Ca) + 1*MM(C) + 3*MM(O)

= 1*40.08 + 1*12.01 + 3*16.0

= 100.09 g/mol

mass of CaCO3 = 1*10^2 g

mol of CaCO3 = (mass)/(molar mass)

= 1*10^2/1.001*10^2

= 0.9991 mol

According to balanced equation

mol of CO2 formed = moles of CaCO3

= 0.9991 mol

Given:

V = 25.0 L

n = 0.9991 mol

T = 600.0 oC

= (600.0+273) K

= 873 K

use:

P * V = n*R*T

P * 25 L = 0.9991 mol* 0.08206 atm.L/mol.K * 873 K

P = 2.863 atm

Answer: 2.86 atm