How many molecules of nitrogen dioxide are in 1.28 g of nitrogen dioxide?

In order to determine the number of molecules of nitrogen dioxide that are in 1.28 g of nitrogen dioxide, we first need to know these values:

Molar mass of nitrogen dioxide = 46.0055 g/mol

Avogadro's number = 6.022 x 10^23 molecules/mol

Then, we divide 1.28 g by the molar mass and multiply the resulting value to Avogadro's number:

1.28 g / 46.0055 g/mol x 6.022 x 10^23 molecules/mol = 1.6755 x 10^22 molecules of nitrogen dioxide