When a few drops of phenolphthalein are added to a dilute solution of sodium hydroxide, a pink colour is produced. What will be the colour of the final mixture when excess of HCI is added to it ? (jusify your answer)

Arrange the metals iron, magnesium, zinc and copper in the increasing order of their reactivity. What will be the two observations made by the student when iron filings are added to copper sulphate solution ?

Explanation

Phenolphthalein acquires pink colour in sodium hydroxide solution because of its basic nature. On adding excess of HCl, the solution will become acidic and the solution will change colour from pink to colourless.
Or
The increasing order of the reactivity of metals is :
`CultFeltZnltMg.`
The displacement reaction taking place in aqueous solution is :
`Fe(s)+underset("(Blue)")(CuSO_(4)(aq))rarrunderset("(Light green)")(FeSO_(4)(aq))+underset("(Brown)")(Cu(s))`
The observations made from the experiment are :
(i) Colour of the solution will change from blue to light green.
(ii) Brown deposit will be formed at the bottom of the tube.