Question

What is the identity of 51g of a gas in a 24.5L container at 25.0oC and 1.5atm?

H2S

H2O

N2

C2H6

Answer 1

We know that PV = nRT

Where

T = Temperature = 25 oC = 25 + 273 = 298 K

P = pressure = 1.5 atm

n = No . of moles = ?

R = gas constant = 0.0821 L atm / mol - K

V= Volume of the gas = 24.5 L

Plug the values we get

n = (PV) / (RT)

= ( 1.5x24.5)( 0.0821x298)

= 1.50 moles

We know that Number of moles , n = mass/molar mass

So Molar mass , M = mass/number of moles

                             = 51 g / 1.50 mol

                             = 33.9

                             ~ 34 g/mol

The molar mass of H₂S is = (2xAt.mass of H) + At.mass of S

                                      = (2x1) + 32

                                      = 34 g/mol

Therefore the identity of the gas is H₂S