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Magnesium carbonate has the formula MgCO₃ - Edexcel - GCSE Chemistry Combined Science - Question 6 - 2022 - Paper 1
Question 6
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 6 - 2022 - Paper 1
Step 1
What is the electronic configuration of the Mg²⁺ ion?
Answer
The electronic configuration of magnesium is given by the filling of electrons in atomic orbitals. For Mg, which has an atomic number of 12, the electron configuration is:
- Neutral Mg: 2 electrons in the first shell and 8 in the second (2.8).
- Upon losing 2 electrons to form Mg²⁺, the configuration becomes 2.
Thus, the correct answer is B 2.8.
Step 2
Explain why solid magnesium carbonate cannot conduct electricity but solid magnesium can.
Answer
Solid magnesium carbonate (MgCO₃) cannot conduct electricity because its ions are fixed in a lattice structure and cannot move freely to carry charge. In contrast, solid magnesium has delocalized electrons that can move, allowing it to conduct electricity. This mobility of electrons in solid magnesium enables it to transfer electric charge, making it a good conductor.
Step 3
Calculate the percentage by mass of magnesium in magnesium carbonate, MgCO₃.
Answer
To calculate the percentage by mass of magnesium in MgCO₃, we first determine the molar mass of MgCO₃:
- Molar mass of Mg = 24.0 g/mol
- Molar mass of C = 12.0 g/mol
- Molar mass of O (3 atoms) = 3 × 16.0 g/mol = 48.0 g/mol
Therefore, the total molar mass of MgCO₃ is:
Next, we find the percentage by mass of magnesium:
Thus, the percentage by mass of magnesium in MgCO₃ is approximately 28.57%.