why we use kmno4 and h2so4 in making carboxylic acid from alkane and not used k2cr2o7 it have large no. of oxygen

Though K2Cr2O7 has a larger no of oxygen atoms asscoiated with it though it is a weak oxidising agent than KMnO4/H+. this is becoz on reduction K2Cr2O7 with Cr having oxidation no +6 forms Cr3+ ion as such it can give 3 electrons to the overall reaction for oxidation. However Acidified KMnO4 with Mn having oxidation state +7 get reduced to Mn2+ as such it can contribute 5 electron to the overall reaction.