Determine the mass of 4 moles of Methane (CH₄) gas.

Given: Number of moles of methane gas = 4
             The chemical formula of methane gas = CH₄
Formula:   
Number of moles = Mass of substance (m) / (Molar mass of given substance (M)  
Solution:
Molar mass of CH₄ (M) = 1X atomic mass of carbon + 4 X atomic mass of hydrogen 
                                        = 1X 12 + 4X 1
                                        = 16g
Number of moles of methane gas = Mass of methane (m) / Molar mass of methane (M) 
                                              4                      =   m/16
                                             4 X 16              =   m
                                                m = 64g
The mass of 4 moles of methane gas is 64g.