finding quite tricky help me plsssss
You can use the molar mass of oxygen gas (O2) and Avogadro's number as conversion factors in this problem. The molar mass is good for "g→mol" or "mol→g" conversions. Avogadro's number is good for "molecules→moles" or "moles→molecules" conversions.
Avogadro's number is the number of things (6.022 x 1023) in a mole of things (e.g., there are 6.022 x 1023 molecules of O2 in one mole of O2).
Molar masses are found on the periodic table. The molar mass of an element is the mass, in grams, of a mole of atoms for each element. It is 16.00 g/mol for O. Because there are two O atoms in O2, the molar mass for O2 is 32.00 g/mol.
The calculation can be planned out like this, because we have conversion factors for each of the two steps.
grams O2 → mol O2 → molecules O2
And the calculation steps are set up this way:
250 g O2 x (1 mol O2 / 32.00 g O2) x (6.022 x 1023 molecules O2 / 1 mol O2)
= 4.7 x 1024 molecules