Question

How many moles of NH3 are there in 77.5 g of NH3?

Answer 1

4.56 moles because

77.5 given mass

17 molar mass

moles will be 77.5/17

i.e. 4.56 moles

Answer 2

So, 5 moles of NH3 will contain 3 × 5 × 6.023 × 10²³ H atoms. 1 mole ammonia having 6.022*10^23 molecule. Three H atoms per molecule, so it would be 3 moles of H per mole of ammonia and then multiply it by 5.