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Magnesium carbonate has the formula MgCO₃ - Edexcel - GCSE Chemistry - Question 3 - 2022 - Paper 1
Question 3
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 - Question 3 - 2022 - Paper 1
Step 1
What is the electronic configuration of the Mg²⁺ ion?
Answer
The electronic configuration of the Mg²⁺ ion can be determined by noting that magnesium (atomic number 12) has the electronic configuration of 2.8. When it loses two electrons to form Mg²⁺, it will have an electronic configuration of 2. Therefore, the correct answer is:
A 2.
Step 2
Explain why solid magnesium carbonate cannot conduct electricity but solid magnesium can.
Answer
Solid magnesium can conduct electricity because it contains free-moving electrons that can carry charge throughout its structure. In contrast, magnesium carbonate, which is an ionic compound, does not have free-moving ions when solid. Although it contains charged ions (Mg²⁺ and CO₃²⁻), they are held in fixed positions within the solid structure and cannot move freely to conduct electricity.
Step 3
Calculate the percentage by mass of magnesium in magnesium carbonate, MgCO₃.
Answer
To calculate the percentage by mass of magnesium in magnesium carbonate, we first need to determine its molar mass.
- Relative atomic mass of Mg = 24.0
- Relative atomic mass of C = 12.0
- Relative atomic mass of O = 16.0 (with three oxygen atoms in MgCO₃)
The molar mass of MgCO₃ is:
Now, to find the percentage by mass of magnesium:
ext{Percentage by mass of magnesium} = rac{ ext{Mass of Mg}}{ ext{Molar mass of MgCO₃}} imes 100 = rac{24.0}{84.0} imes 100 = 28.57\ ext{%}
Step 4