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A student investigates the energy released when hydrochloric acid completely neutralises sodium hydroxide solution - AQA - GCSE Chemistry - Question 8 - 2015 - Paper 3
Question 8
A student investigates the energy released when hydrochloric acid completely neutralises sodium hydroxide solution. The student uses the apparatus shown in Figure 4.... show full transcript
Worked Solution & Example Answer:A student investigates the energy released when hydrochloric acid completely neutralises sodium hydroxide solution - AQA - GCSE Chemistry - Question 8 - 2015 - Paper 3
Step 1
Suggest a cause for the anomalous result when 20 cm³ of hydrochloric acid is added.
Answer
Possible causes for the anomalous result could include incorrect measurement of temperature or volume, incorrect recording of temperature, failure to stir the solution properly, or heat loss during the experiment.
Step 2
Step 3
Step 4
Step 5
Use your answers to 8(a)(iii) and 8(a)(iv) and the equation to calculate the energy released in the reaction. Give the unit.
Answer
Using the equation Q = mcΔT:
- m = 55 g (since 55 cm³ is equivalent to 55 g)
- c = 4.2 J/g°C
- ΔT = 20 °C
Thus, the energy released, Q = 55 g × 4.2 J/g°C × 20 °C = 4620 J.
Step 6
Explain why starting with 50 cm³ of sodium hydroxide solution instead of 25 cm³ would make no difference to the overall temperature increase.
Answer
Starting with 50 cm³ instead of 25 cm³ of sodium hydroxide does not affect the overall temperature increase because the amount of hydrochloric acid added will still completely neutralise the sodium hydroxide. The total energy change depends on the amount of acid and alkali mixed, not their individual volumes.