Question Video: Identifying the Period 4 Metal Found in a Potassium Compound with a Violet Color in Solution Chemistry

Video Transcript

The following picture shows a potassium compound dissolving in water. This compound is commonly used in laboratories to oxidize other chemicals. Which of the following period four metals does it also contain atoms of? (A) Chromium, (B) nickel, (C) scandium, (D) manganese, (E) zinc.

In this question, we want to find out which period four metal is part of the compound that is shown dissolving in water. Answer choices (A) through (D) are transition metals, and transition metal ions are known for their variety of colors. For example, in aqueous solution, the chromium three plus ion has a dark green color, while the nickel two plus ion is pale green. The scandium three plus ion is colorless, and the manganese two plus ion is pale pink.

While none of these ions have the deep purple color we can see in the center of the picture, manganese is worth investigating further. Due to its large number of oxidation states, manganese can form a wide variety of ions. Some of these ions are polyatomic ions that contain oxygen, known as oxyanions. The color of these ions in solution varies widely. However, we notice that the MnO4− ion produces a violet color in solution. The name of this ion is the permanganate ion.

We are told that the picture shows a potassium compound in water. Therefore, the compound must be potassium permanganate, or KMnO4. Potassium permanganate is a well-known oxidizing agent, which means that it can be used to oxidize other chemicals. Because of its oxidizing properties, potassium permanganate is used as a disinfectant, as a fungicide, and in water treatment.

In conclusion, the potassium compound shown dissolving in water is potassium permanganate, which is composed of potassium, manganese, and oxygen atoms. Therefore, the period four metal that the compound contains is manganese, or answer choice (D).