Calculate the mass fraction of hydrogen in the chemical formula NaH.

In order to calculate the mass fraction of an element in a compound, we use the general formula w = n * A (E) / M (X), where w is the mass fraction of an element, n is the number of atoms of this element in the formula, A (E) is its atomic mass, M (X) is the molecular mass of the compound.
The molar mass of NaH = 24, the atomic mass of hydrogen = 1, in the compound NaH there is 1 hydrogen atom. Hence, w (H) = 1 * 1/24 = 0.0417, or w (H) = 0.0417 * 100% = 4.17%
Answer: the mass fraction of hydrogen in the NaH compound is 4.17%