Question

What do you see when penta hydrated copper-sulfate crystals are heated? Give a reaction too.

Answer 1

Hint: We know the chemical formula of copper sulphate is $CuS{O_4}.5{H_2}O$ and it has five water molecules. On heating copper sulphate forms blue crystals.

Complete step by step answer: We know that the copper sulphate has five water molecules which on heating the five water molecules present in the copper sulphate are lost due to evaporation. When water or hydrations are lost copper sulphate forms blue color anhydrous copper sulphate.
Now we can write the chemical equation for the above reaction is,
$CuS{O_4}.5{H_2}O\xrightarrow{\Delta }CuS{O_4} + 5{H_2}O$
Anhydrous copper sulphate on further heating undergoes a decomposition reaction to give black copper (II) oxide that is cupric oxide, oxygen and sulfur dioxides are released during the reaction.
Now we can write the chemical reaction of decomposition of copper sulphate is given as,
$2CuS{O_4}\xrightarrow{\Delta }2Cu + {O_2} + 2S{O_2}$

Additional Information:
Now we discuss about decomposition reaction as,
The decomposition reaction:
If a compound breaks down to two or more substances then it is a decomposition reaction. The general equation for the reaction is,
$AB\xrightarrow{{}}A + B$
Now we see the double decomposition reaction.
The reaction in which the two reactants interchange their positive and negative ions and form a new compound is called a double decomposition reaction. The general equation of the reaction is,
$AB + CD\xrightarrow{{}}AD + CB$
There are three types of decomposition reactions and which are discussed below as,
Thermal decomposition reaction: We know that the decomposition reaction is activated by the thermal energy is defined as a thermal decomposition reaction. The decomposition of Calcium Carbonate is a suitable example of a thermal decomposition reaction. We can write chemical equation for the above reaction is,
$CaC{O_3}\xrightarrow{\Delta }CaO + C{O_2}$
Electrolytic decomposition reaction: The decomposition reaction which is activated by the electrical energy is defined as an electrolytic decomposition reaction. The electrolysis of water is a suitable example of an electrolytic decomposition reaction. We can write the chemical equation for the above reaction is,
$2{H_2}O\xrightarrow{{}}2{H_2} + {O_2}$
Photolytic decomposition reaction: The decomposition reaction in reactants broken down to simpler substances by absorbing energy from photons is defined as a photolytic decomposition reaction. The decomposition of ozone is a suitable example of a photolytic decomposition reaction and we can write the chemical equation for the above reaction is,
${O_3} + h\gamma \xrightarrow{{}}{O_2} + {O^.}$

Note: We must remember that anhydrous salts are the salts which do not have water molecules. Copper sulfate is a hydrated salt which when heated, loses its water molecules and gives anhydrous copper sulfate. In the agricultural field, copper sulfate is used as fungicides for preparation of Bordeaux and Burgundy mixture.