Question

How many molecules (not moles) of NH, are produced from 7.83x10-4 g of H, ?

Answer 1

1)

Molar mass of NH3,
MM = 1*MM(N) + 3*MM(H)
= 1*14.01 + 3*1.008
= 17.034 g/mol

mass of NH3 = 7.83*10^-4 g
mol of NH3 = (mass)/(molar mass)
= 7.83*10^-4/17.03
= 4.597*10^-5 mol


Balanced chemical equation is:
2NH3 ---> 3H2 + N2


According to balanced equation
mol of H2 formed = (3/2)* moles of NH3
= (3/2)*4.597*10^-5
= 6.895*10^-5 mol

use:
number of molecules = number of mol * Avogadro’s number
number of molecules = 6.895*10^-5 * 6.022*10^23 molecules
number of molecules = 4.152*10^19 molecules
Answer: 4.15*10^19 molecules

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