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Investigating acid reactions and salt preparation

Chemical changes • Reactions of acids

Key concepts

What you'll likely be quizzed about

  • Exothermic reactions release energy to the surroundings, resulting in a measurable rise in solution temperature.
  • Examples include reactions of acids with metals and acid-base neutralisation.
  • In contrast, endothermic reactions absorb energy, causing a temperature drop; certain dissolution processes exemplify this phenomenon.
  • Temperature change serves as a direct indicator of net energy transfer but does not specify which bonds break or form; comprehensive energy accounting needs to consider all steps and surroundings.

Flashcards

Test your knowledge with interactive flashcards

Which formula estimates heat transferred to a solution during a reaction?

Click to reveal answer

The formula is q = m × c × ΔT, where q is heat (J), m is mass of solution (g), c is specific heat capacity (J g−1 °C−1), and ΔT is temperature change (°C).

Key notes

Important points to keep in mind

q = m × c × ΔT calculates heat change for solution.

Higher concentration usually produces larger ΔT for the same volume.

Use insulation and a lid to reduce heat loss in calorimetry.

Add excess insoluble oxide/carbonate to ensure complete reaction.

Filter off unreacted solid before crystallisation.

Evaporate only to the point of crystallisation, not to dryness.

Wash crystals with cold solvent to remove impurities.

Dry crystals at low temperature to avoid decomposition.

Gas evolution can reduce measured ΔT by carrying away heat.

Account for the calorimeter’s heat capacity or minimize its effect.

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