Question

When the solution of substance X is added to a solution of potassium iodide, then a yellow solid separates out from the solution.

1. What do you think substance X is likely to be?
2. Name the substance which the yellow solid consists of.
3. Which characteristic of chemical reactions is illustrated by this example?
4. Write a balanced chemical equation for the reaction which takes place. Mention the physical states of all the reactants and products involved in the chemical equation.

Answer 1

1. Substance X is likely to be lead nitrate (Pb(NO₃)₂), because on reacting with potassium iodide, it forms a yellow precipitate.
2. The yellow solid or precipitate consists of lead iodide (PbI₂), which is one of the products in this reaction.
3. This chemical reaction is characterised by the formation of a precipitate.
4. \[\ce{2KI_{(aq)} + Pb(NO3)2_{(aq)} -> PbI2_{(s)} + 2KNO3_{(aq)}}\]