Why we add Sulfuric Acid for Preparation of Satandard Solution of Mohr's Salt

For the preparation of standard solution of Mohr’s Salt during titration, it is necessary to add dilute Sulfuric Acid to prevent the Fe2+ ions of Mohr’s salt solution from undergoing oxidation to Fe3+ ions.

But here, Nitric Acid (HNO3) or Hydrochloric Acid (HCl) cannot be used.

• Why We Cannot Add Nitric Acid?                                                                Since Nitric Acid is very strong oxidizing agent so, the Fe2+ ions present in in Mohr’s salt solutions will be oxidized both by Potassium Permanganate(KMnO4) and Nitric Acid(HNO3), which will result in an error in determination of volume of volume of KMnO4 reacting with Mohr’s salt solution.
• Why We Cannot Add Hydrochloric Acid?                   Hydrochloric Acid (HCl) cannot be used in preparation of standard solution of Mohr’s Salt because Cl- ion  in HCl will be oxidized by Potassium Permanganate(KMnO4).

---