The compounds in fireworks also contain non-metal ions. A scientist tests a solution of the chemicals used in a firework. Silver nitrate solution and dilute nitric acid are added to the solution. A cream precipitate forms. Which ion is shown to be present by the cream precipitate?

The test described is the standard chemical test for halide ions. First, dilute nitric acid is added to remove any other ions that might form a precipitate (like carbonate ions). Then, silver nitrate solution is added. The silver ions (Ag⁺) react with any halide ions present to form a silver halide precipitate, which is insoluble. The colour of the precipitate identifies the specific halide ion: - **Silver chloride (AgCl)** is a **white** precipitate. - **Silver bromide (AgBr)** is a **cream** precipitate. - **Silver iodide (AgI)** is a **yellow** precipitate. Since a cream precipitate was formed, the ion present must be the bromide ion (Br⁻).