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

answers: to make sure that all of the broken pieces of tablet were added to the water, to allow for fair comparison of all three trials, with different particle sizes to avoid experimental error