Henry

In true, the occurred reaction are the following: First stage: IO3+ + 3HSO3- --> I- + 3H+ + 3SO42- Second stage: I- + IO3+ + H+ --> I2 + H2O Third stage: I2 + corn starch --> blue compound Fourth stage: I2 + HSO3- + H2O --> 2I- + SO42- + 3H+ so, my trouble is to know what is the enthalpy of first-fourth stage system. The yours explanations was useful, thanks. But, For this total system, the enthalpy will go to increase or to decrease, considering the four stages as a whole?

If I've this two following solutions: A - 0,5g of KIO3 in 250 mL of H2O; B - 1g of starch dissolved in 250 mL of boiling H2O. Add 0,2g of NaHSO3 and 5 mL of sulfuric acid 6M solution. Dilute in 500 mL of water. And if I mix it, will the reaction be endothermic or exothermic? Thanks. (excuse I post this topic in organics. I do not perceived it)