What is copper sulfate

Copper sulfate is an inorganic compound that combines copper and sulfate. In its liquid or powdered form it’s most commonly called basic copper sulfate, BSC copper fungicide, CP basic sulfate, or tri-basic copper sulfate. In its solid, crystal-shaped stone form (known as a pentahydrate) it’s known as blue stone or blue vitriol for its blue color. In this form, it’s a popular raw material for producing other types of copper salts.

Copper sulfate

Preparation CuSO4

Copper Sulfate can be prepared by the redox reaction of copper metal and concentrated sulphuric acid in high temperatures:

Cu + H2SO4 → CuSO4

The copper metal is oxidized to the cation Cu2+, within this reaction. Similarly, we can also prepare it by reacting copper with diluted sulphuric acid and air.

Properties of CuSO4

The physical and chemical properties of copper sulfate are discussed in this subsection. It can be noted that the properties of anhydrous CuSO4 and CuSO4.5H2O vary considerably, and have been highlighted separately.

1. Physical Properties

  1. The molar mass of the anhydrous and the pentahydrate forms of copper sulfate are 159.609 grams/mole and 249.685 grams per mole respectively.
  2. Anhydrous CuSO4 has a grey-white, powdery appearance whereas the pentahydrate has a bright blue colour.
  3. The densities of the anhydrous and pentahydrate forms are 3.6 grams per cubic centimetre and 2.286 g.cm-3
  4. Both hydrated and anhydrous copper sulfates tend to decompose on heating and hence do not have exact boiling points.
  5. Anhydrous CuSO4 has an orthorhombic crystal structure whereas CuSO4.5H2O crystals have triclinic structures.

2. Chemical Properties

  1. The copper ions present in copper sulfate react with the chloride ions belonging to concentrated hydrochloric acid, leading to the formation of tetrachlorocuprate(II).
  2. The chemical equation for this reaction is given by Cu2+ + 4Cl– → CuCl42-
  3. When heated to 650oC, CuSO4 undergoes a decomposition reaction to yield cupric oxide (CuO) and SO3 (sulfur trioxide).
  4. Copper sulfate is highly soluble in water, with solubility values of 1.055 molal and 1.502 molal at 10oC and 30oC respectively.
  5. A typical example of a single displacement reaction where one metal displaces another is the reaction between iron and copper sulfate, given by the reaction Fe + CuSO4 → FeSO4 + Cu

Uses of CuSO4

Copper Sulfate has the most common use in the form of a fungicide and a herbicide because of its toxicity. Further, it is beneficial in the treatment of fruits like melons and berries to control fungus and parasites.

Moreover, in organic synthesis, it acts as a dryer agent and as a catalyst in some reactions. Copper Sulfate is also used as a dye in some vistrals and paints.

Why is anhydrous copper sulphate white and the pentahydrate blue?

In hydrated CuSO4, the water molecules surrounding the Central Metal (Cu) act as ligands resulting in d-d transition and therefore emitting blue colour in the visible region due to which hydrated CuSO4 appears blue. Since anhydrousCuSO4 does not hold any water of crystallization, It retains its white colour.