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Temperature change when the concentration of a solution is increased?

The standard enthalpy change for the reaction of calcium hydroxide with
hydrochloric acid was found by reacting 0.0100 mol of solid calcium hydroxide
with 50.0 cm3 of a 1.00 mol dm–3 solution of hydrochloric acid (an excess), in a
polystyrene cup. The temperature rose from 21.2 °C to 26.7 °C.

The experiment was repeated again using 25 cm3 of 2.00 mol dm−3
hydrochloric acid. Predict the temperature change in this experiment.

The mark scheme says that the answer is that the temperature doubles. How exactly? Both experiments are using 0.5 mol of the acid, right?

This is from Edexcel, Jan 2010 Unit 3B.

Reply 1

EierVonSatan

If you lit a fire in a small room, would you expect that the same fire would heat a room twice the size to the same average temperature?

Reply 2

githz

Isn't it just coz the concentration doubles and therefore temperature doubles. Acid is used in excess so the halved volume has no effect.

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Reply 3

Borek

Original post by githz

Isn't it just coz the concentration doubles and therefore temperature doubles. Acid is used in excess so the halved volume has no effect.

Concentration doesn't matter. Calcium hydroxide is the limiting reagent, so in both cases amount of heat produced is identical - but in the second case mass that is heated up is two times lower.