A student was given the following substances and was asked to show types of chemical reactions through experiment. Write how he would have done that.
Copper sulphate solution, barium chloride solution, ferrous sulphate crystals, Iron nails, calcium oxide, water.

Explanation

Given chemicals are `CuSO_(4)` solution, `BaSO_(4)` solution, iron nails `(Fe)`, Ferrous sulphate `(FeSO_(4))`, Calcium oxide `(CaO)` and water `(H_(2)O)`
i) Chemical combination :
Chemicals chosen : `CaO, H_(2)O`
`CaO+H_(2)Orarr Ca(OH)_(2)`
When we add water to calcium oxide it produces Calcium hydroxide. This is an example for chemical combination.
ii) Chemical decomposition :
Chemicals chosen : Ferrous sulphate
`2FeSO_(4)overset("Heat")rarr Fe_(2)O_(3)+SO_(2)+SO_(3)`
When we heat `FeSO_(4)` it dissociates into Ferric oxide, Sulphur dioxide and Sulphur trioxide respectively.
iii) Chemical displacement :
Chemicals chosen : Iron nail `- CuSO_(4)`
`Fe+CuSO_(4)rarr FeSO_(4)+Cu darr`
When iron nail is placed in `CuSO_(4)` solution, hte solution turns into light green due to formation of `FeSO_(4)` reddish brown deposit of Copper.
iv) Double displacement :
Chemicals chosen : `CuSO_(4)` solution and `BaCl_(2)` solution.
`CuSO_(4(aq))+BaCl_(2(aq))rarr BaSO_(4(s))darr+CuCl_(2(s))`
When `CuSO_(4)` is mixed with `BaCl_(2)` solution it forms white precipitate of `BaSO_(4)` and aqueous solution of Copper (II) Chloride.
This is an example for double displacement reaction.