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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 co... 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 electronic configuration of magnesium (atomic number 12) is represented as 2.8. Therefore, when it loses two electrons to form the Mg²⁺ ion, the configuration becomes 2. This corresponds to option A. Thus, the correct answer is A.
Step 2
Explain why solid magnesium carbonate cannot conduct electricity but solid magnesium can.
Answer
Solid magnesium carbonate (MgCO₃) is composed of ions held together in a rigid lattice structure, preventing them from moving freely. Consequently, the ionic components cannot transport electric charge. In contrast, solid magnesium is a metal, with its atoms arranged in a way that allows free electrons to move throughout the structure. This electron mobility in solid magnesium enables it to conduct electricity.
Step 3
Calculate the percentage by mass of magnesium in magnesium carbonate, MgCO₃.
Answer
To find the percentage by mass of magnesium in magnesium carbonate, first calculate 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 = 16.0 g/mol (and there are 3 O atoms, so total O mass = 3 × 16.0 = 48.0 g/mol)
Total molar mass of MgCO₃ = 24.0 + 12.0 + 48.0 = 84.0 g/mol.
Now, use the formula for percentage by mass:
ext{Percentage of Mg} = rac{ ext{mass of Mg}}{ ext{mass of MgCO}_3} imes 100
Substituting the values:
= 28.57 ext{%}.$$