Describe the oxidising action of potassium dichromate and write the ionic equations for its reaction with: (i) iodide (ii) iron(II) solution and (iii) H2S
Potassium dichromate is a powerful oxidizing agent in acidic medium. In the presence of dilute sulphuric acid, it liberates nascent oxygen. K2Cr2O7+4H2SO4→K2SO4+Cr2(SO4)3+4H2O+ Nascent oxygen 3(O) In acidic medium, dichromate ion takes up electrons and acts as an oxidizing agent. Cr2O72−+14H++6e−→2Cr3++7H2O The net ionic equations for its reaction with (i) iodide (ii) iron(II) solution and (iii) H2S are as shown below. Cr2O72−+6I−+14H+→2Cr3++3I2+7H2O Cr2O72−+6Fe2++14H+→2Cr3++6Fe3++7H2O Cr2O72−+3H2S+8H+→2Cr3++3S+7H2O
