GCSE / O Levels Chemistry

The table shows the observations made when an aqueous solution of salt Z has different
reagents added to it.
reagent(s) added
observation
aqueous sodium hydroxide
green precipitate formed
dilute nitric acid
white precipitate formed
then
aqueous barium nitrate
What is Z?
A copper(II) chloride
B copper(II) sulfate
C iron(II) chloride
D iron(II) sulfate


Choice D is correct because:

When an aqueous solution of iron(II) sulfate is reacted with aqueous sodium hydroxide, a green precipitate of iron(II) hydroxide (Fe(OH)2) is formed, which aligns with the first observation. 

Furthermore, when dilute nitric acid and aqueous barium nitrate are added to the solution, a white precipitate of barium sulfate (BaSO4) is formed. This matches the second observation. 

Therefore, iron(II) sulfate, is the most suitable match based on the given information.

Choices A, B and C are incorrect because they do not match the observed reactions.

Identification of Ions and Gases | 2016 - O/N - 5070/12 | Q25