Cobalt Complexes and Color Changes

The video tutorial by Chris Harris explores variable oxidation states in cobalt chemistry, focusing on Cobalt 2+ and Cobalt 3+ ions. It discusses the oxidation of Cobalt 2+ in alkaline solutions using hydrogen peroxide, forming Cobalt 3+ complexes. The tutorial also covers oxidation using ammonia, highlighting the formation of different cobalt complexes and their color changes. The effects of excess ammonia and aerial oxidation on cobalt complexes are also examined, providing a comprehensive understanding of cobalt chemistry.

What are the two main cobalt ions discussed in the video?

• Cobalt 1+ and Cobalt 3+

• Cobalt 3+ and Cobalt 4+

• Cobalt 2+ and Cobalt 3+

• Cobalt 1+ and Cobalt 2+

Which oxidizing agent is used to oxidize Cobalt 2+ in an alkaline solution?

• Oxygen

• Sodium hydroxide

• Ammonia

• Hydrogen peroxide

What is the color of Cobalt 2+ when dissolved in solution?

• Blue

• Pink

• Orange

• Green

What complex is formed when Cobalt 2+ is oxidized in the presence of hydroxide ions?

• Cobalt chloride complex

• Cobalt hexa hydroxide complex

• Cobalt ammonia complex

• Cobalt hexa aqua complex

How does ammonia act when added in small amounts to a Cobalt hexa aqua complex?

• As an acid

• As an oxidizing agent

• As a catalyst

• As a base

What is the color change observed when Cobalt 2+ is oxidized using ammonia?

• Pink to blue

• Blue to pink

• Orange to green

• Green to orange

What happens when excess ammonia is added to the Cobalt complex?

• It forms a precipitate

• It forms a charged complex

• It remains unchanged

• It decomposes

What is the final color of the solution when Cobalt 2+ is oxidized to Cobalt 3+ using aerial oxidation?

• Green

• Orange

• Pink

• Blue

What role does ammonia play when added in excess to the Cobalt complex?

• It acts as a base

• It acts as a ligand

• It acts as an acid

• It acts as a reducing agent

Which of the following is true about charged complexes?

• They are insoluble in solution

• They form precipitates

• They are soluble in solution

• They decompose quickly