AP Chem -
Which element is oxidized in the following reaction:
CuO(s) + H2 (g) Cu(s) + H2O (l)
Oxidation is the loss of electrons.
Cu is +2 on the left and zero on the right.
H2 is zero on the left and +1 on the right.
CU oxidizes
To determine which element is oxidized in a chemical reaction, you need to compare the oxidation states of the elements before and after the reaction.
In the given reaction, CuO(s) + H2 (g) → Cu(s) + H2O (l), we have copper (Cu) and hydrogen (H2) involved.
Let's determine the oxidation states of copper (Cu) before and after the reaction:
CuO(s): Cu is in the +2 oxidation state in CuO. Oxygen (O) is generally assigned a -2 oxidation state. Therefore, since the compound is neutral, the sum of the oxidation numbers should be zero. Thus, the oxidation state of copper is +2.
Cu(s): Copper by itself is an element, and its oxidation state is 0.
By examining the oxidation states, we can see that the oxidation state of copper changes from +2 in CuO to 0 in Cu.
Now, let's consider the oxidation states of hydrogen (H2) before and after the reaction:
H2(g): Hydrogen in a diatomic molecule like H2 is assigned an oxidation state of 0 since it is not bonded to any other element.
H2O(l): Each hydrogen in water (H2O) usually has an oxidation state of +1. Oxygen generally has an oxidation state of -2, so for water to be neutral, each hydrogen should have an oxidation state of +1.
From the above analysis, we observe that the oxidation state of hydrogen changes from 0 in H2 to +1 in H2O.
In this reaction, copper (Cu) undergoes a decrease in oxidation state from +2 to 0, while hydrogen (H2) undergoes an increase in oxidation state from 0 to +1. According to the definition of oxidation, the element that undergoes an increase in oxidation state is oxidized. Therefore, hydrogen is the element that is oxidized in this reaction.