This question is about salts - AQA - GCSE Chemistry Combined Science - Question 2 - 2019 - Paper 1

The correct formula for nitric acid is HNO₃.

The colour observed in nitric acid is red, while in ammonia solution, it turns blue.

The correct answer is row D.

The percentage by mass of oxygen can be calculated as follows:

• Determine the relative formula mass of NH₄NO₃:

  • M = 14 (N) + 4 * 1 (H) + 3 * 16 (O) = 80

• Total mass of oxygen = 3 * 16 = 48

• Percentage by mass of oxygen: $\text{Percentage} = \left( \frac{48}{80} \right) \times 100 = 60\%$

The investigation method can be described in the following steps:

1. Use a suitable container, such as a test tube.
2. Measure a specific volume of water and place it in the test tube.
3. Record the initial temperature of the water, using a thermometer.
4. Weigh out different masses of ammonium nitrate (choose at least three different masses).
5. Add each mass of ammonium nitrate one at a time to the water in the test tube.
6. Stir the solution to ensure proper dissolution of the ammonium nitrate.
7. Measure and record the final temperature of the solution after each addition.
8. Calculate the temperature change for each mass of ammonium nitrate dissolved.
9. Repeat the process for accuracy.