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5.0 g samples of the carbonates of barium, copper, lithium and magnesium are decomposed to the metal oxides and carbon dioxide - CIE - A-Level Chemistry - Question 4 - 2018 - Paper 1
Question 4
5.0 g samples of the carbonates of barium, copper, lithium and magnesium are decomposed to the metal oxides and carbon dioxide. For which compound is there the grea... show full transcript
Worked Solution & Example Answer:5.0 g samples of the carbonates of barium, copper, lithium and magnesium are decomposed to the metal oxides and carbon dioxide - CIE - A-Level Chemistry - Question 4 - 2018 - Paper 1
Step 1
For which compound is there the greatest loss in mass?
Answer
To find the compound with the greatest loss in mass when decomposed, we need to consider the molar masses of each carbonate and the decomposition products.
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Identify the carbonates:
- Barium carbonate (BaCO₃)
- Copper(II) carbonate (CuCO₃)
- Lithium carbonate (Li₂CO₃)
- Magnesium carbonate (MgCO₃)
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Calculate the molar masses:
- BaCO₃:
- Ba: 137.33 g/mol
- C: 12.01 g/mol
- O (3): 3 × 16.00 g/mol
- Total: 137.33 + 12.01 + 48.00 = 197.34 g/mol
- CuCO₃:
- Cu: 63.55 g/mol
- C: 12.01 g/mol
- O (3): 48.00 g/mol
- Total: 63.55 + 12.01 + 48.00 = 123.56 g/mol
- Li₂CO₃:
- Li (2): 2 × 6.94 g/mol
- C: 12.01 g/mol
- O (3): 48.00 g/mol
- Total: 2 × 6.94 + 12.01 + 48.00 = 73.89 g/mol
- MgCO₃:
- Mg: 24.31 g/mol
- C: 12.01 g/mol
- O (3): 48.00 g/mol
- Total: 24.31 + 12.01 + 48.00 = 84.32 g/mol
- BaCO₃:
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Determine mass loss upon decomposition:
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The general reaction is:
ext{M}_x ext{CO}_3 ightarrow ext{M}_x ext{O} + ext{CO}_2
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The loss in mass during decomposition is essentially the mass of the CO₂ produced.
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Loss of mass (in grams) = mass of carbonate (5.0 g) - mass of metal oxide produced.
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Greatest loss in mass will correspond to the highest molar mass of CO₂ released:
- CO₂ has a molar mass of 44.01 g/mol.
- Therefore, the compound with the least mass left after decomposition will be lithium carbonate, which decomposes to produce the highest volume of CO₂ relative to its initial mass.
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Conclusion:
- Out of the given options, lithium carbonate (C) results in the greatest loss in mass during thermal decomposition.