A student carries out a titration to find the concentration of a sodium carbonate solution using dilute nitric acid.
The table below shows the student's results:
| Titration number | 1 | 2 | 3 | 4 |
|---|---|---|---|---|
| Volume of acid (cm3\text{cm}^3cm3) | 18.9 | 17.5 | 17.3 | 17.4 |
The student decides that the best value for the mean (average) volume of acid is 17.4 cm317.4\text{ cm}^317.4 cm3.
Show how she calculated this value.
The chemical equation for this reaction is:
2HNO3+Na2CO3→2NaNO3+H2O+CO2 2\text{HNO}_3 + \text{Na}_2\text{CO}_3 \rightarrow 2\text{NaNO}_3 + \text{H}_2\text{O} + \text{CO}_2 2HNO3+Na2CO3→2NaNO3+H2O+CO2The table below shows the relative formula masses (MrM_rMr) for each substance:
| Substance | Relative formula mass, MrM_rMr |
|---|---|
| HNO3\text{HNO}_3HNO3 | 63 |
| Na2CO3\text{Na}_2\text{CO}_3Na2CO3 | 106 |
| NaNO3\text{NaNO}_3NaNO3 | 85 |
| H2O\text{H}_2\text{O}H2O | 18 |
| CO2\text{CO}_2CO2 | 44 |
Water and carbon dioxide are waste products in this reaction, while sodium nitrate is the desired product.
Calculate the atom economy for this reaction to produce sodium nitrate. Give your answer to 1 decimal place.
81 exam-style questions on OCR GCSE Chemistry Improving processes and products. Each one has a worked solution and a mark scheme showing where the marks go.