Explanation:
Balanced chemical reaction equation will be as follows.
In human body, the neutral iron changes into 
(aq) cation. There will be an oxidation-half reaction and a reduction-half reaction. Equations for this reaction are as follows.
Oxidation: 2Fe^{2+}(aq) \rightleftharpoons 2Fe^{3+}(aq) + 2e^{-}[/tex] .... (1)
Reduction: 
...... (2)
On adding both equation (1) and (2), the overall reaction equation will be as follows.
Therefore, neutral iron is a part of Heme - b group of Hemoglobin and in an aqueous solution it dissolutes as a part of Heme group. Hence, then it becomes an cation.
Answer is: an instant ice pack becoming cold, splitting a gas molecule and baking bread.
<span>Endothermic reaction
is chemical reaction that absorbs more energy than it releases.
</span>In ice pack, <span>reaction absorbs heat from the surroundings (endothermic reaction), lowering the surrounding temperature.
For splitting molecule and baking bread we must add energy to break bonds between atoms.</span>
Because H is a non-metal, it has the highest electronegativity. Option (1) H is correct.
Hope this would help~
