Final answer:
Diluted sulfuric acid is used in KMnO4 titrations because, unlike nitric acid, it is not a strong oxidizing agent under the conditions of the titration, ensuring accuracy without interfering with the titrant reactions.
Step-by-step explanation:
You've noted that diluted H2SO4 is used as the medium in KMnO4 titration, but HNO3 is not used because it is an oxidizing agent. The reason that HNO3 is not suitable for this purpose is primarily due to its strong oxidizing properties, especially under the acidic conditions of a titration. While hot, concentrated sulfuric acid also acts as an oxidizer, diluted H2SO4 does not possess the same oxidizing power. When titrating with KMnO4, the presence of a strong oxidizing agent like HNO3 could interfere with the reaction by competing with the KMnO4 as an oxidizer.
Nitric acid is a very strong oxidizing agent, potentially causing side reactions by oxidizing the substances you intend to titrate with the KMnO4. This would lead to inaccurate results. In contrast, diluted sulfuric acid does not oxidize the substances being titrated under typical titration conditions, thus allowing for accurate measurements.
Furthermore, in the presence of strong acids like H2SO4 and HNO3, the proton-transfer equilibria lie far to the right, with the reaction of these acids with water forming solutions of the H3O+ ion and the conjugate base of the acid. However, H2SO4 is generally preferred over HNO3 in KMnO4 titration because of its non-oxidizing nature when diluted, ensuring that the presence of H2SO4 does not interfere with the redox titration process.