While sulphur dioxide and hydrogen peroxide can act as oxidising as well as reducing agents in their reaction ozone and nitric acid act only as oxidatns .Why ?

Explanation

A species can act as both oxidant and reductant if any one of its constitument atoms has an intermediate value of oxidation number .So in a reaction the atom can increase or decrease its oxidation number i.e it can acts as an oxidation as well as a reductant.
In `SO_(2)`the oxidation number of S is +4 .The highest and lowest oxidation numbers of S are +6 and -2 respectively .Therefore , S - atoms in `SO_(2)` is able to increase its oxidation number in a reaction in which `SO_(2)` acts as a reductant and decrease its oxidation number in a reaction in which `SO_(2)` plays a role of an oxidation .Hence,`SO_(2)` can acts as an oxidant as well as a reductant.
2 In `H_(2)O_(2)` ,the oxidation number of O is -1 The highest and lowest oxidation numbers of oxygen are -2 and 0 respectively .Therefore,oxygen atom in `H_(2)O_(2)` is capable of increasing or decreasing its `H_(2)O_(2)` is capable of increasing or decreasing its oxidation number .The reaction in which` H_(2)O_(2)`acts as an oxidant ,the oxidation number of oxygen decreases from -1 to -2 and the reaction in which it acts as a reduction ,the oxidation number of oxygen increases from -1 to 0 .Hence `H_(2)O_(2)` can acts both as an oxidant and a reductant.
3 In `O_(3)` ,the oxidation number of oxygen is zero. Oxygen can show two oxidation number -1 and -2 . So, the oxidation number of oxygen in `O_(3)` can reduce to -1 or -2 but in can never increases .Hence ,`O_(3)` can act only as an oxidant.
4 In `HNO_(3)` ,the oxidation number of nitrogen is +5 .It is the maximum oxidation number that nitrogen can exhibit .So the Only opportunity for nitrogen in `HNO_(3)` is to decrease its oxidation number .Hence `HNO_(3)` can act only as an oxidant .