Use the chemical equation to complete the activity. H2(g) + I2(g) → 2HI(g) A student makes the following statements: Hydrogen always has the same oxidation number, so it has an oxidation number of +1 in both the reactant H2 and product HI. Iodine is in Group VIIA, so it has an oxidation number of –1 in both the reactant I2 and product HI. Neither hydrogen nor iodine changes oxidation states, so the reaction is not a redox reaction. In three to five sentences, describe the mistake that the student made, and determine whether or not the reaction is a redox reaction. Explain your answer.
The student made a mistake in assuming that hydrogen always has an oxidation number of +1. In this specific reaction, hydrogen exists in its diatomic form (H2), which means that each hydrogen atom has an oxidation number of 0. However, in the product HI, each hydrogen atom does indeed have an oxidation number of +1. Hence, hydrogen does change its oxidation state in this reaction. On the other hand, iodine does have an oxidation number of -1 in both the reactant I2 and the product HI. This means that the reaction is indeed a redox reaction because both hydrogen and iodine change their oxidation states.
talk like a 8th grader
The student made a mistake in thinking that hydrogen always has an oxidation number of +1. But in this chemical equation, hydrogen is still H2, so its oxidation number is actually 0. But when it becomes HI, each hydrogen has an oxidation number of +1. So, the hydrogen does change its oxidation number in the reaction. On the other hand, iodine does stay at -1 in both I2 and HI. So, since both hydrogen and iodine change their oxidation numbers, the reaction is a redox reaction.
