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Magnesium carbonate has the formula MgCO₃ - Edexcel - GCSE Chemistry Combined Science - Question 2 - 2022 - Paper 1
Question 2
Magnesium carbonate has the formula MgCO₃. (a) Magnesium carbonate contains Mg²⁺ and CO₃²⁻ ions. (i) The atomic number of magnesium is 12. What is the electronic ... show full transcript
Worked Solution & Example Answer:Magnesium carbonate has the formula MgCO₃ - Edexcel - GCSE Chemistry Combined Science - Question 2 - 2022 - Paper 1
Step 1
What is the electronic configuration of the Mg²⁺ ion?
Answer
The atomic number of magnesium (Mg) is 12, which means it has 12 electrons in its neutral state. When it loses two electrons to form the Mg²⁺ ion, its electronic configuration changes. The configuration for magnesium is originally 2.8. Therefore, for Mg²⁺, it becomes 2, which corresponds to option A.
Step 2
Explain why solid magnesium carbonate cannot conduct electricity but solid magnesium can.
Answer
Solid magnesium carbonate (MgCO₃) consists of ions held together in a rigid lattice structure that prevents the movement of ions. Thus, it cannot conduct electricity. In contrast, solid magnesium consists of metal atoms that have free electrons in a 'sea' of electrons, allowing them to move freely and conduct electricity.
Step 3
Calculate the percentage by mass of magnesium in magnesium carbonate, MgCO₃.
Answer
First, we calculate the relative formula mass of magnesium carbonate:
- Relative atomic mass of Mg = 24.0
- Relative atomic mass of C = 12.0
- Relative atomic mass of O = 16.0 (and there are 3 oxygen atoms)
Total mass of MgCO₃ = 24.0 + 12.0 + (3 × 16.0) = 24.0 + 12.0 + 48.0 = 84.0
To find the percentage by mass of magnesium:
Substituting the values: