An atom of aluminium has an atomic mass of 27 - Edexcel - GCSE Chemistry - Question 5 - 2022 - Paper 1

The atomic mass of aluminium is 27. The number of neutrons can be calculated by subtracting the atomic number from the atomic mass:

Number of neutrons = Atomic mass - Atomic number = 27 - 13 = 14.

The atomic number also indicates that aluminium has 13 protons.

To find the empirical formula, first determine the number of moles of aluminium and bromine.

For aluminium:

a. Molar mass of Al = 27 g/mol

b. Moles of Al = mass (g) / molar mass (g/mol) = 1.35 g / 27 g/mol = 0.05 mol

For bromine:

a. Molar mass of Br = 80 g/mol

b. Moles of Br = 12.00 g / 80 g/mol = 0.15 mol

Next, find the simplest mole ratio:

0.05 mol Al : 0.15 mol Br = 1 : 3

Thus, the empirical formula of aluminium bromide is AlBr₃.