Heat of Displacement

Heat of displacement is the energy change when one mole of metal is displaced from its salt solution by a more electropositive metal

  1. Displacement reaction occurs when a metal which is situated at a higher position in the electrochemical series displace a metal below it from its salt solution.
  2. Heat of displacement is the energy change when one mole of metal is displaced from its salt solution by a more electropositive metal
  3. Displacement reaction is always an exothermic reaction.
  4. Example below shows how the heat of displacement can be calculated.

Example:
A student pours 50cm³ hydrochloric acid, 2 mol/dm³ into a plastic beaker, and records its temperature. Some zinc powder (excess) is added into the acid. The solution is stirred by using a glass rod, and the highest temperature that reach by the mixture is recorded.

Initial temperature of the solution: 27.0°C
Highest temperature of the solution: 57.0°C

Find the heat of displacement of the reaction.
[Specific heat capacity of the solution = = 4.2 Jg-1°C-1, density of the solution =1 g/cm³ ]
Answer:
2HCl(ak) + Zn(p) → ZnCl2 (ak) + H2(g)

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