Question

The mass of one atom of an element X is 2.0 × 10^–23 g.
(i) Calculate the atomic mass of element X.
(ii) What could element X be ?

Answer 1

Given:
Mass of an atom of element X = 2.0 × 10^-23g
We know that the mass of an atom of a substance is equal to the mass of 1 mole of that substance. 1 mole of a substance consists of 6.022 × 10²³ atoms; therefore, the mass of an atom of a substance is equal to the mass of 6.022 × 10²³ atoms.
Therefore, to calculate the atomic mass of element X, we need to calculate the mass of 6.022 × 10²³ atoms of X.
Mass of 1 atom of X = 2.0 × 10^-23
Mass of 6.022 × 10²³ atoms of X = 6.022 × 10²³ × 2.0 × 10^-23 = 12 u
Hence, the atomic mass of element X is 12 u.
Carbon has an atomic mass of 12 u; therefore, element X is carbon.