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Some metal carbonates cannot be obtained in a pure state - CIE - A-Level Chemistry - Question 2 - 2016 - Paper 1
Question 2
Some metal carbonates cannot be obtained in a pure state. For example magnesium carbonate exists in a 'basic' form, in which magnesium hydroxide is also present. On... show full transcript
Worked Solution & Example Answer:Some metal carbonates cannot be obtained in a pure state - CIE - A-Level Chemistry - Question 2 - 2016 - Paper 1
Step 1
Method
Answer
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Weigh a crucible with its lid and record the mass. This is the mass of the crucible and lid, denoted as ( m_{crucible} ).
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Add 1.1–1.3 g of FB 4 (basic magnesium carbonate) to the crucible and weigh the crucible again. Record this total mass as ( m_{total} ).
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Calculate the mass of FB 4 used: [ \text{Mass of FB 4} = m_{total} - m_{crucible} ]
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Heat the crucible and contents as described and allow for the residue to form after heating.
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Once cooled, replace the lid and re-weigh the crucible with its contents. Record this as ( m_{final} ).
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Determine the mass of the residue obtained after heating: [ \text{Mass of residue} = m_{final} - m_{crucible} ] This will help in determining the mass loss during the decomposition of magnesium carbonate.
Step 2
Results Calculation
Answer
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Prepare a table to record all measurements, ensuring appropriate headings like 'Mass of Crucible and Lid', 'Mass of FB 4 before heating', and 'Mass after heating'.
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Record the mass values accurately with correct units (grams) to maintain clarity.
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Finally, use the recorded masses to analyze the decomposition reaction and relate it to the expected formula.