SO2 turns lime water milky. SO2 in aqueous solution gives H2SO3. H2SO3⇌H++HSO3− CO2 also turns lime water milky. CO2 in aqueous solution gives H2CO3. H2CO3⇌H++HCO3− H2SO3 is stronger acid than H2CO3. Thus, ionisation of H2SO3 is larger than H2CO3. Thus, pH of H2SO3 is lower than that of H2SO2.