Acidified potassium permanganate solution is decolourised by Mohr’s salt. Hence option c is the right answer. Mohr’s Salt, also referred to as ammonium iron(II) sulfate, is an inorganic compound whose chemical formula is represented as (NH4)2Fe(SO4)2(H2O)6. Potassium permanganate is a common chemical compound that combines manganese oxide ore with potassium hydroxide. It was first developed as a disinfectant in 1857.