A student prepares calcium nitrate, a soluble salt, using dilute nitric acid and insoluble calcium carbonate.
The table shows the student's method and observations.
| Stage | Method or observation |
|---|---|
| 1 | Warm the dilute nitric acid. |
| 2 | Add calcium carbonate in small portions. All the solid disappears. A pH probe gives a reading of 2. |
| 3 | Filter the mixture. |
| 4 | Heat the filtrate strongly until all the water has evaporated. |
A calcium ion is Ca2+\text{Ca}^{2+}Ca2+ and a nitrate ion is NO3−\text{NO}_3^-NO3−. The student writes this equation for the reaction:
CaCO3+HNO3→CaNO3+H2O+CO2\text{CaCO}_3 + \text{HNO}_3 \rightarrow \text{CaNO}_3 + \text{H}_2\text{O} + \text{CO}_2CaCO3+HNO3→CaNO3+H2O+CO2
Explain the two errors in the student's equation.
Use the pH reading to explain what is wrong with stage 2 and how the student should change it.
Suggest how stage 4 should be changed to produce well-formed crystals of calcium nitrate. Give a reason for your answer.
88 exam-style questions on AQA GCSE Chemistry 4.2 Reactions of acids, covering 4.2.1a Reactions of acids with metals, 4.2.1b Redox in acid-metal reactions, 4.2.2 Neutralisation of acids and salt production, 4.2.3 Soluble salts, 4.2.4 The pH scale and neutralisation, 4.2.5a Titrations, 4.2.5b Calculating quantities in titrations, and 4.2.6 Strong and weak acids. Each one has a worked solution and a mark scheme showing where the marks go.