Question

Which one will liberate $B{r_2}$ from KBr?
A. ${I_2}$
B. $S{O_2}$
C. HI
D. $C{l_2}$

Answer 1

Hint: Bromine is a good oxidising agent which is useful and does not readily decompose. It has the tendency to liberate iodine from iodine containing solutions. It tends to oxidise the sulfurous acid to sulphuric acid by bromine water. So to approach this question we need to know the concept of oxidising agent and should know among all these which one is a stronger oxidising agent than bromine.

Complete step by step solution:
We know that bromine tends to exist in group seven and has the ability to occur in various states which include liquid and gas both. It has reddish brown color in liquid state which is used widely in agriculture and in dyestuff areas.

So now let us see how bromine liberated. When the chlorine is bubbled in the solution of potassium bromide it tends to turn into bright red colour as the bromide ions get oxidised into bromine element. The balanced equation for the reaction of chlorine with potassium bromide is the following:
$C{l_2} + KBr \to B{r_2} + 2KCl$

So we came to know that the chlorine would liberate bromine from the potassium bromide solution. But the reason behind it is the electronegativity. So the electronegativity is the ability of an atom to attract the shared electrons in the covalent bond. We know that the size of chlorine is huge and it needs only one electron to fill its valence shell and get stabilized but because of its large size the nucleus tends to pull the electrons. This stronger pull of the nucleus causes the high electronegativity for the atoms which are present in the same row of the periodic table. So due to this the chlorine tends to replace bromine and could oxidise it.

Hence the correct answer is option D.

Note: The bromine has high electron affinity but it is a less powerful oxidising agent than chlorine. Bromine is bleach in its fluid form and it is dangerous for human skin and respiratory tracts. Remember that the solution of iodine does not tend to replace bromine because bromine is more reactive than iodine.