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An atom of aluminium has an atomic mass of 27 - Edexcel - GCSE Chemistry - Question 5 - 2022 - Paper 1
Question 5
An atom of aluminium has an atomic mass of 27. Aluminium has an atomic number of 13. State the number of electrons, neutrons and protons in this atom. (a) number o... show full transcript
Worked Solution & Example Answer:An atom of aluminium has an atomic mass of 27 - Edexcel - GCSE Chemistry - Question 5 - 2022 - Paper 1
Step 1
State the number of electrons, neutrons and protons in this atom.
Answer
The atomic number of aluminium is 13, which is equal to the number of electrons in a neutral atom. Therefore, the number of electrons is 13.
To find the number of neutrons, we subtract the atomic number from the atomic mass: Number of neutrons = Atomic mass - Atomic number = 27 - 13 = 14.
The number of protons is equal to the atomic number, hence the number of protons is also 13.
Step 2
Calculate the empirical formula of this sample of aluminium bromide.
Answer
First, we need to calculate the number of moles of each element:
-
For aluminium (Al):
Molar mass of Al = 27.0 g/mol.
Number of moles of Al =
= \frac{1.35}{27.0} = 0.05 ext{ moles}.
-
For bromine (Br):
Molar mass of Br = 80.0 g/mol.
Number of moles of Br =
= \frac{12.00}{80.0} = 0.15 ext{ moles}.
Next, calculate the ratio of moles:
- Ratio of Al to Br = \frac{0.05}{0.05} : \frac{0.15}{0.05} = 1 : 3.
Thus, the empirical formula of aluminium bromide is AlBr₃.