Question

How many molecules of carbon dioxide are there in 44.0 grams of the gas? (atomic mass of carbon = 12.0 and atomic mass of oxygen = 16.0)

Answer 1

first find the number/amount of moles of CO2 (carbon dioxide) present.

to do that use the relationship:

moles=mass/molar mass which in chemistry is written as n=m/M

ps. molar mass is also called atomic mass, molecular mass, molecular weight, Daltons, etc.

then once you have the amount of moles you multiply it by a proportional constant, Avogadros number, 6.023 x 10^23.

A lot of people get confused by this, think of it like this:

1 dozen = 12
1 mole = 6.023 x 10^23 (atoms, molecules, particles, whatever)

so, use n=m/M

then multiply n by 6.023 x 10^23