A sample of air tums lime water milky and also turns acidified potassium dichromate green in aqueous solution has low pH. This is due to the presence of pollutants

SO2 tums lime water milky.SO2 in aqueous solution gives H2SO3H2SO3 ⇌  H+ +HSO3−CO2 also turns lime water milky.CO2 in aqueous solution gives H2CO3H2CO3 ⇌  H+ +HCO3−H2SO3 is stronger acid than H2CO3. Thus, ionization of H2SO3 is larger than H2CO3.Thus, pH of H2SO3 is lower than that of H2CO3.SO2 also tums acidified K2Cr2O7 solution green.3SO2 +Cr2O72−  +  2H+ →   3SO42− +  2Cr3+Green  +H2OThus, air sample has SO2 as pollutants.