exothermic + endothermic reactions

when a chemical reaction occurs, energy is transferred to or from the surroundings - and there is often a temp. change
exothermic reactions
1. transfer energy to the surroundings
2. usually energy is transferred as heat energy, causing the reaction mixture and its surroundngs to be become hotter
3. e.g. combustion, oxidation reactions (rusting), neutralisation between acids + alkalis
endothermic reactions
1. take energy in from the surroundings
2. usually transferred as heat energy, causing the reaction mixture + its surroundings to become colder
3. e.g. electrolysis, the reaction between ethanoic +sodium carbonate, the thermal decomposition of calcium carbonate in a blast furnace
reversible reactions
1. in reversible reactions, the reaction in 1 direction will be exothermic + the reaction in the other direction will be endothermic
2. the decomposition of ammonium chloride is a reversible reaction:
  1. ammonium chloride -> ammonia + hydrogen chloride
  2. ammonium chloride <- ammonia + hydrogen chloride
  3. ammonium chloride decomposes when it's heated, so the forward reaction is endothermic
    1. energy must be transferred from the surroundings for it to happen
  4. the backward reaction is endothermic
    1. energy is transferred into the surroundings when it happens

Resource summary

	Created by charlotte_lucy_9 about 11 years ago