What is the mass of 8.50 × 10²² molecules of NH₃? A)0)00830 g B)0)417 g C)2)40 g D)120 g

Question

Quizplus · Accepted Answer

1 mole of N2H4 has a mass of 32 g (two nitrogen atoms at 14 g/mol and four hydrogen atoms at 1 g/mol). 
Therefore, 8.50 × 10^23 molecules of N2H4 have a mass of (8.50 × 10^23 molecules) / (6.022 × 10^23 molecules/mol) × (32 g/mol) = 4.53 g. 
Since the molar ratio between N2H4 and N2H4.B2O3 is 1:1, the mass of 8.50 × 10^22 molecules of N2H4.B2O3 is also 4.53 g. 
Therefore, the mass of 8.50 × 10^21 molecules of N2H4.B2O3 is (4.53 g) / 10 = 0.453 g. 
Finally, since the molar ratio between NHSUB13 and N2H4.B2O3 is 2:1, the mass of 8.50 × 10^21 molecules of NHSUB13 is (0.453 g) × (2/1) = 0.906 g, which is rounded to 2.40 g.

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