Question

calculate no of miles ,no of molecules and no of atoms present in 3.4g NH3

Answer 1

the molar mass (reading from the period table ) is 17.031g/mol.
therefore 3.4 grams of ammonia is equal to 0.1996359579590159 moles of ammonia.
multiplying this by 6.022*10^23 we get 120220773889374980000 molecule(or 1.2022*10^23 molucles)
in 1 molecule of ammonia there are 4 atoms
the measurement was made using 2 significant figures,so we can only be sure about this result to 2 significant figure,therefore the amount of atoms in 3.4g of ammonia is approx 4.8*10^23 atoms
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