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.
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Answer
A potential cause for the anomalous result could be a failure to stir the solution properly, leading to uneven temperature distribution.
Step 2
Suggest the true value of the temperature of the anomalous point.
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Answer
The true value of the temperature at the anomalous point is approximately 32-33 °C.
Step 3
What was the total volume of the mixture when the maximum temperature was reached?
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The total volume of the mixture when the maximum temperature was reached is 55 cm³.
Step 4
Calculate the overall temperature increase in this experiment.
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Answer
The overall temperature increase in this experiment is 20 °C.
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.
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Using the formula Q = mcΔT, where m = 55 g (mass of solution), c = 4.2 J/g°C, and ΔT = 20 °C, the energy released can be calculated as:
Q=55imes4.2imes20=4620extJ
Thus, the energy released is 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.
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Starting with 50 cm³ of sodium hydroxide solution would not affect the overall temperature increase, as the reaction's enthalpy change remains the same regardless of the initial volume, provided that there is sufficient hydrochloric acid to completely neutralize the sodium hydroxide.
