Your strategy here will be to use the molar mass of nitric oxide, NO, to determine how many moles you get in that sample.
Once you know that, you can use Avogadro’s number as a conversion factor to help you determine how many molecules would be present in that many moles.
So, nitric oxide has a molar mass of 30.1gmol
which means that one mole of nitric oxide has a mass of 30.01 g.
Since your sample is about 8 g short of the mass of one mole, you can say for a fact that you’re dealing with less than one mole of nitric oxide.
More precisely, you will have
Now, according to Avogadro’s number, one mole of any substance contains 6.022.10
molecules of that substance. This means that 0.7498 moles of nitric oxide will contain
Rounded to three sig figs, the number of sig figs you have for the mass of nitric oxide, the answer will be
no of molecules 4.52×10