Example-3: A 50.0cm3 sample of water taken from a location in Dubai was first saturated with oxygen and then left for a period of 5 days at 293K in the dark. The Winkler method was carried out to measure the dissolved oxygen content in the water sample before and after the 5-day incubation period. The following is the series of reactions related to the method: Mn(aq)2++2OH(aq)Mn(OH)2(s)2Mn(OH)2(s)+O2(g)2MnO(OH)2(s)MnO(OH)2(s)+4H(aq)++2I(aq)Mn(aq)2++I2(aq)+3H2O(l)I2(aq)+2S2O32(aag)2I(aq)+S4O6(aq)2 It was found that 5.25cm3 of a 0.00500moldm3 solution of sodium thiosulfate, Na2S2O3, was required to react with the iodine produced. a) Determine the concentration of dissolved oxygen, in mgdm3, in the sample of water. b) Deduce BOD. (Solubility of O2 in water is 9mgdm3 at 293K )