# Calculate the mass fraction (%) of each element in ammonia (NH3).

March 27, 2021 | education

| Formula for calculating the mass fraction of an element in a substance:

w = n * Ar (chemical element) / Mr (substance), where n is the number of atoms of a given chemical element.

1) Find the relative molecular weight of the substance (NH3):

Mr (NH3) = Ar (N) + 3 * Ar (H) = 14 + 3 = 17;

2) Find the mass fraction of a given element in the substance:

w (N) = 14/17 = 0.82 or 82%;

1 way: w (H) = 3/17 = 0.18 or 18% or 2 way: w (H) = 100 – 82 = 18%.

Answer: Mass fraction of nitrogen in ammonia is 82%. Mass fraction of hydrogen in ammonia is 18%.

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