# Calculate the mass fraction of hydrogen in the CH4 and CaH2 compounds.

July 26, 2021 | education

| Given:

CH4

CaH2

To find:

ω (H in CH4) -?

ω (H in CaH2) -?

Solution:

1) Using the periodic system of D.I.Mendeleev, calculate the relative molecular weights of CH4 and CaH2:

Mr (CH4) = Ar (C) + Ar (H) * 4 = 12 + 1 * 4 = 16;

Mr (CaH2) = Ar (Ca) + Ar (H) * 2 = 40 + 1 * 2 = 42;

2) Calculate the mass fraction of H in CH4:

ω (H in CH4) = N * Ar (H) * 100% / Mr (CH4) = 4 * 1 * 100% / 16 = 25%;

3) Calculate the mass fraction of H in CaH2:

ω (H in CaH2) = N * Ar (H) * 100% / Mr (CaH2) = 2 * 1 * 100% / 42 = 4.76%.

Answer: Mass fraction of H in CH4 is 25%; H in CaH2 – 4.76%.