Question

List observations when iron is dipped in dilute sulphuric acid.

Answer 1

Hint: Iron is a metal with chemical formula $Fe$ which is an element of group $13$ of the d-block elements. ${H_2}S{O_4}$ is the formula for sulphuric acid (which is considered as a strong acid). So, the above reaction is a reaction in which an acid reacts with a metal and the products formed are a salt and evolution of hydrogen gas $({H_2})$ .

Complete answer:
The given reaction is between the iron metal and dilute sulphuric acid:
$Fe + {H_2}S{O_4} \to FeS{O_4} + {H_2}$
The reaction between the Fe metal and sulphuric acid is a type of displacement reaction. In this type of reaction stronger (more reactive according to the reactivity series) metal or element displaces other elements from it’s compound.
Reactivity of elements is given by reactivity series in which the order of reactivity of metals in decreasing order is as follows:-
$K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au$
Hence, from the above reactivity series, we can see that Iron metal is much more reactive than the Hydrogen, so hydrogen can be easily displaced by iron from ${H_2}S{O_4}$ and forms a salt with the formula $FeS{O_4}$ and Hydrogen displaced is released (evolved) in the form of hydrogen gas $({H_2})$.
So, the observations of this reaction are:
(i) A green colour solution will be formed due to the formation of Ferrous sulphate, $FeS{O_4}$ .
(ii) Hydrogen gas is released in the above reaction.

Note:
The reaction given above releases (evolves) hydrogen gas and tests for the hydrogen gas can be done by an experiment. When a burning candle is taken close to the hydrogen gas bubbles, it burns with a pop sound and it can be inferred that the gas released is hydrogen gas because only hydrogen gas burns with a pop sound.