(a) Heat energy change at constant pressure
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(b)
Indicative Chemistry
Stage 1: Apparatus
1a. Use a burette/pipette (instead of a measuring cylinder)
1b. Use a polystyrene cup (instead of a beaker) / insulate beaker
1c. Reweigh the watchglass after adding the solid 1d: Use powdered solid
Stage 2: Temperature Measurements
2a. Measure and record the initial temperature of the solution for a few minutes before addition
2b. Measure and record the temperature after the addition at regular intervals (eg each minute) for 8+ minutes/until a trend is observed
Stage 3: Temperature Determination
3a. Plot a graph of temperature against time
3b. Extrapolate to the point of addition
3c. Determine ΔT at the point of addition
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(c) n(HCl) or n(NaOH) = 50 x 0.500 / 1000 = 0.025 moles
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q = –ΔH x n = 57.1 x 0.025 = 1.4275 kJ
M2 = 57.1 × M1
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ΔT = q/mc
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ΔT = (1.4275 x 1000) / (100 x 4.18) = 3.4(2) °C
M4 = (M2 × 1000) / (100 × 4.18)
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Final Temperature = 18.5 + 3.4 = 21.9 °C
M5 = M4 + 18.5 (but final temperature must be higher than 18.5 °C)
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(d) Increase the concentration of the solutions
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