Is this half-reaction H2(g) + 2 OH-(aq) ===> 2 H2O(l) = 2 e
reduction or oxidation?
H2 goes from zero on the left [H2[(g) to +1 on the right (in H2O). The O is -2 on the left and -2 on the right. The H (in OH^-) is +1 on the left and +1 on the right (in H2O). So the change is from H2(g) on the left at zero to +1 on the right in H2O. To go from zero to +1 H had to (lose,gain) electrons.
This is an oxidation reaction then, right?
The given half-reaction H2(g) + 2 OH-(aq) → 2 H2O(l) + 2 e- involves a gain of electrons (e-), which means that the species undergoing the reaction is being reduced. Therefore, the given half-reaction is a reduction.
To determine whether the given half-reaction is a reduction or oxidation, you can follow these steps:
1. Identify the element or compound that undergoes a change in oxidation number.
In the given half-reaction, the element that undergoes a change in oxidation number is hydrogen (H2).
2. Determine the initial oxidation state and final oxidation state of that element or compound.
In the reactant side of the half-reaction, hydrogen is present in its elemental form (H2), which has an oxidation state of 0. In the product side of the reaction, hydrogen is present in the compound H2O, where its oxidation state is +1.
3. Analyze the change in oxidation number.
In this case, hydrogen changes from an oxidation state of 0 to +1. The change is from a lower oxidation state to a higher one.
Based on these steps, it can be concluded that the given half-reaction is an oxidation.
Explanation of the steps:
1. The first step involves identifying the element or compound that undergoes a change in oxidation number because oxidation and reduction involve changes in oxidation states.
2. The next step is to determine the initial and final oxidation states of the identified element or compound to observe the change in oxidation number during the reaction.
3. By analyzing the change in oxidation number, you can determine whether it is an increase (oxidation) or a decrease (reduction). In this case, since the oxidation state of hydrogen increased from 0 to +1, it indicates oxidation.