Answer: you will need to work out how many moles are in NH3, to get this you divide the mass by NH3's RMM (relative molecular formula) [14+(3x1)=17]
5.00/17=0.294 moles
so now that you've got the moles to get molecules you need to times the moles by avargado's constant 6.022x10^23
the rule is that one mole of compound containes 6.022x10^23 molecules
so now you times your moles of NH3 (0.294) by avargados constant
0.294 x 6.002x10^23 = 1.765x10^23
just to clarify thats 1.765 times ten to the power of 23
Explanation: hope this helps:)