Chromium (VI) is a toxic and carcinogenic element; it could be detected in waste water getting out from many industries as tannery, textile and electroplating of metals. Oxidation reduction process is the most economic and simple way of removing Cr6+ by conversion into Cr3+ (non hazard). The rate of reduction reaction of Cr6+ to Cr3+ in K2Cr2O7 has been studied in absence of nontoxic acids and it is found to be first order reaction. Different acids as acetic acid, mono, di and trichloro acetic acid were also tested at different temperature and reaction. The rate of the reaction in each case was measured. Thermodynamic parameters ΔG*, ΔH* and ΔS* are given.