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10 (a) A sample of potassium carbonate is contaminated with a small amount of sodium carbonate - Edexcel - GCSE Chemistry - Question 10 - 2019 - Paper 1
Question 10
10 (a) A sample of potassium carbonate is contaminated with a small amount of sodium carbonate. When a flame test is carried out on the sample, a bright yellow flame... show full transcript
Worked Solution & Example Answer:10 (a) A sample of potassium carbonate is contaminated with a small amount of sodium carbonate - Edexcel - GCSE Chemistry - Question 10 - 2019 - Paper 1
Step 1
Describe how you could show that potassium and sodium ions are present in this sample.
Answer
To confirm the presence of potassium and sodium ions in the sample, you can perform a flame test.
- Flame Test Procedure: Take a small amount of the solid sample and place it on a clean platinum wire or a wooden splint.
- Observation: Hold the splint in a Bunsen burner flame.
- Expected Results: If potassium ions are present, a lilac or purple flame will be produced, confirming their presence. Sodium ions will produce a bright yellow flame, which is typical for sodium when it is present in the sample.
- Comparison: Use known reference samples for potassium and sodium salts to compare the flame colors for accuracy.
Step 2
Write the ionic equation for this reaction.
Answer
The ionic equation for the reaction between hydrochloric acid and sodium carbonate can be derived as follows:
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Identify the reactants and products:
- The reactants are hydrochloric acid (HCl) and sodium carbonate (Na2CO3).
- The products are sodium chloride (NaCl), carbon dioxide (CO2), and water (H2O).
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Write the complete ionic equation:
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Cancel the spectator ions: Sodium ions (Na+) and chloride ions (Cl-) do not participate in the reaction. Therefore, the net ionic equation is: