Question Video: Recalling the Product of a Metal-Metal Oxide Displacement Reaction Chemistry

Video Transcript

When calcium reacts with cesium oxide, a displacement reaction occurs. What are the products of the reaction?

A displacement reaction is a reaction where one group of a compound is replaced by another, like this. In this example, the group B is being replaced by C. You can also get something called a double displacement, where two groups from two different compounds swap with one another. In this case, the reactants are calcium and cesium oxide. Calcium has the symbol Ca while cesium oxide has the symbol Cs2O.

If you look at your periodic table, you’ll see that cesium is in group one. This means it has one electron in its outer shell and forms ions with a single positive charge. Oxygen, on the other hand, is in group 16. It has six electrons in its valence shell and can gain two more to form an octet, forming oxygen two minus. In the compound cesium oxide, we need two equivalents of cesium in order to counteract the two minus charge of the oxide, giving us the formula Cs2O.

One of the products of this reaction is calcium oxide. Calcium has two electrons in its outer shell and is therefore in group two and forms calcium two plus ions. Therefore, only one equivalent of calcium two plus is required to counterbalance the negative charge of oxygen two minus.

The second product of this reaction is pure cesium. In this reaction, oxygen has migrated from cesium over to calcium. Or, to put it another way, the calcium has displaced the cesium. Therefore, when calcium reacts with cesium in a displacement reaction, the products of the reaction are calcium oxide and cesium. You could’ve done this without the intervening equation simply by substituting the name of the metal ions, calcium with cesium.