Question

The formula for methane is CH₄ and it’s molar mass is 16.04 grams/mol.

(a) How many moles of methane are in 2.750 grams of methane?

(b) How many molecules of methane are in a 11.5 mole sample?

Answer 1

Given molar mass of methane , M = 16.04 g/mol

(a) mass of metahne , m = 2.750 g

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

                                                   = 2.750 g / 16.04 (g/mol)

                                                   = 0.17 moles

(b) We know that 1 mole of any compound contains avagadro number (6.023x10²³) molecules

So 11.5 moles of methane contains 11.5 mol x ( 6.023x10²³ molescules / 1 mol )

                                                    = 6.93x10²⁴ molecules