Question: A student added few pieces of aluminium metal to two test tubes A and B containing aqueous solution of iron sulphate and copper sulphate. In the second part of her experiment, she added iron metal to another test tube C and D containing aqueous solution of aluminium sulphate and copper sulphate. In which test tube or test tubes will she observe colour change? On the basis of this experiment state which one is the most reactive metal and why? [CBSE, 2018]
Answer: Only in test tubes A, B and D she will observe colour change from green to colourless in A because aluminium is more reactive than iron, it will displace iron. She will observe colour change from green to colourless in test tube B. She will also observe colour change in test tube D from blue to light green. Aluminium is the most reactive metal because it displaces all the other three metals.