Reversible Reactions & Equilibria (Edexcel IGCSE Science (Double Award): Chemistry): Flashcards

A reversible reaction is one in which the products can react to re-form the original reactants, so the reaction can proceed in both the forward and the reverse direction.

The symbol ⇌ is used, with two half-arrowheads pointing in opposite directions to show the forward and reverse reactions occurring simultaneously.

Heating ammonium chloride causes it to decompose into ammonia gas and hydrogen chloride gas, and these gases recombine on cooling to reform the solid.

True.

Heating ammonium chloride produces ammonia and hydrogen chloride gases, and when these cool they recombine to form solid ammonium chloride again, so the reaction is reversible (NH₄Cl ⇌ NH₃ + HCl).

Hydrated copper(II) sulfate is blue and turns white when heated as it loses its water of crystallisation to form anhydrous copper(II) sulfate.

Adding water to anhydrous copper(II) sulfate is exothermic, and removing water from hydrated copper(II) sulfate by heating is endothermic.

False.

Hydrated copper(II) sulfate (CuSO₄·5H₂O) is blue, but anhydrous copper(II) sulfate (CuSO₄) is white.

Water of crystallisation is water that is chemically incorporated into the crystal structure of a hydrated salt during the crystallisation process, affecting the salt's shape and colour.

A reversible reaction can be made to go in the forward or reverse direction by changing the reaction conditions, such as temperature. Heating hydrated copper(II) sulfate drives the reaction forward (dehydration); adding water reverses it.