Example 2 - Mass of Substance and Number of Particles

Find the mass of methane (CH4) that contain  1.806 x 1023 of methane molecules. [Relative atomic mass: Carbon: 12; Hydrogen: 1]

Answer:
The relative molecular mass of CH4
= 12 + 4(1)
= 16

Number of mole of C H 4 = 1.806× 10 23 6.02× 10 23 =0.3 mole
Mass of CH4
 = Number of mole x molar mass 
= 0.3 x 16 = 4.8g