(a) What is meant by 'a mole of carbon atoms'?(b) Which has more atoms, 50 g of aluminium or 50 g of iron? Illustrate your answer with the help of calculations.(Atomic masses : Al = 27 u ; Fe = 25 u)

(a) A mole can be defined as the amount of a pure substance containing the same number of atoms, molecules or ions as present in exactly 12g of carbon. This refers to the value of 6.022 × 10²³ atoms, molecules or ions of a substance.

(b) Mass of aluminium = 50g

We know that 27g of aluminium contain 6.022 × 10²³ aluminium atoms

Number of aluminium atoms in 27g  aluminium = 6.022 × 10²³

Number of aluminium atoms in 50g aluminium = 50 × 6.022 × 10²³/ 27

Hence, 50g aluminium has 11.15 × 10²³ atoms.

Mass of iron = 50g

We know that 56g  iron contain 6.022 × 10²³ atoms

Number of atoms in 56g iron = 6.022 × 10²³

Number of atoms in 50g  iron = 50 × 6.022 × 10²³ / 56

Hence, 50g iron comprises 5.376 × 10²³ atoms.