How many molecules are in 20.0 g no2

2.62 × 10^23 molecules

We are required to determine the number of molecules in 20.0 g of NO₂

We are going to use the following simple steps;

Moles = Mass ÷ Molar mass

Molar mass of NO₂ = 46.0 g/mol

Therefore;

Moles of NO₂ = 20 g ÷ 46.0 g/mol

                       = 0.435 moles

We need to know, 1 mole of a gas contains molecules equivalent to the Avogadro's number, 6.022 × 10^23.

Therefore; 1 mole of NO₂ = 6.022 × 10^23 molecules

Number of molecules = Moles × Avogadro's number

                                    = 0.435 moles × 6.022 × 10^23 molecules/mole

                                    = 2.62 × 10^23 molecules

Thus, there are 2.62 × 10^23 molecules in 20 g of NO₂

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