A museum laboratory stores two iron salt solutions. Solution P contains iron(II) ions and solution Q contains iron(III) ions. A few drops of sodium hydroxide solution are added to separate samples of P and Q. The precipitates are observed immediately and again after being left exposed to the air.
What are the expected observations?
P gives an orange-brown precipitate immediately, and Q gives a green precipitate that remains green.
P gives a green precipitate that remains green, and Q gives an orange-brown precipitate that slowly turns green.
P gives a green precipitate that slowly turns orange-brown at its surface, and Q gives an orange-brown precipitate immediately.
P and Q both give green precipitates immediately, which slowly turn orange-brown at their surfaces.
107 exam-style questions on OCR GCSE Chemistry 4.2 Identifying the products of chemical reactions, covering 4.2.1 Tests to identify gases, 4.2.2 Tests for aqueous ions and flame tests, and 4.2.3 Instrumental methods of analysis. Each one has a worked solution and a mark scheme showing where the marks go.