Gas Review Problem #4

4)  What is the mass of 3.34 dm³ sample of chlorine gas if the volume was determined at 37^oC and 98.7 kPa?  The density of chlorine gas at STP is 3.17 g/dm³.

Write given information:

•         V₁  =  3.34 L                                     V₂  =  __________
•         T₁  =  37 ^oC  +  273   =  310 K         T₂  =   273  K
•         P₁  =  98.7 kPa                                  P₂  =  101.3 kPa
•         R  =  8.314 kPa L / mol K                  Density  =  3.17 g/dm³
•         n  =  ___________
•         Cl₂  =  71 g/mol

Two approaches to solve this problem.

METHOD 1:  Combined Gas Law & Density

Write equation:       

Substitute into equation:   

Solve for V₂:   V₂  =  2.85 L @ STP

Density  =  3.17 g/dm³ @ STP

Recall:   

Substitute into equation:   

Solve for mass:    mass  =  9.1 g chlorine gas

METHOD 2:  Ideal Gas Law

Write equation:       

Solve for moles::   

Substitute into equation:   

Solve for mole:  n  =  0.128 mol Cl₂

Recall molar mass of diatomic chlorine is 71 g/mol

Calculate mass of chlorine:  x g Cl₂  =  0.128 mol Cl₂  =  9.1 g Cl₂