Calorimetry experiments for determining the enthalpy changes of reactions
2 marks · HardA student adds 25.0 g of water at 22.0 °C to a beaker. After a reaction occurs, the final temperature of the water is 29.5 °C. The specific heat capacity of water is 4.18 J/g°C. Calculate the amount of heat absorbed by the water during the reaction. Give your answer in joules.
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Show answer
785 J (±1)
Common mistakes: Using incorrect temperature change; Wrong units; Rounding incorrectly
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Marking points
M1 · 1 mark · Correctly substitutes values into Q = mcΔT: m = 25.0 g, c = 4.18 J/g°C, ΔT = 29.5 − 22.0 = 7.5 °C.
A1 · 1 mark · Obtains the correct value for Q = 785 J (allow rounding within 1 J).
Worked solution
m = 25.0 g, c = 4.18 J/g°C, ΔT = 29.5 – 22.0 = 7.5 °C
Rounded to the nearest whole number, Q = 785 J.