Question

Carbon and hydrogen are detected by heating the organic compound with
A. Magnesium oxide
B. Cupric oxide
C. zinc oxide
D. sulphur dioxide

Answer 1

Hint: Carbon dioxide can test using lime water test and water can also be tested by using Copper sulphate in anhydrous form. So, we need to use a compound that will help in the transformation of carbon to carbon dioxide and Hydrogen into water.

Complete answer:
The process of detecting any element in an organic compound is referred to as qualitative; with the help of this quantitative analysis we can easily analyze different substituents quantitatively. All organic compounds contain C and Hydrogen. The compounds formed by carbon and hydrogen are also called as an organic compound. There are also various other elements also present like oxygen, nitrogen, phosphorus, sulphur and halogens.
The organic compound is when heated with cupric oxide the carbon present in the compound gets oxidised to carbon dioxide.
\[C + {\rm{ }}2CuO \to \;2Cu{\rm{ }} + {\rm{ }}C{O_2}\]
This carbon dioxide can be tested with the help of lime-water. Carbon dioxide turns lime-water milky. This is due to the formation of precipitation of insoluble calcium carbonate.
\[C{O_2}{\rm{ }} + {\rm{ }}Ca{\left( {OH} \right)_2} \to CaC{O_3}{\rm{ }} + {\rm{ }}{H_2}O\]
Similarly, when an organic compound is heated with cupric oxide the hydrogen present in the compound get oxidised and forms water
\[2H{\rm{ }} + {\rm{ }}CuO{\rm{ }} \to Cu{\rm{ }} + {\rm{ }}{H_2}O\]
It can also be tested with the help of anhydrous copper sulphate. Due to the water formed the anhydrous copper sulphate turns into hydrated copper sulphate.
\[5{H_2}O + {\rm{ }}CuS{O_4} \to CuS{O_4}.5{H_2}O\]

Therefore, the correct option is option (B).

Note: Thus, the hydrogen and the carbon present in the organic compound are detected by heating the organic compound with cupric oxide. Upon heating the carbon forms carbon dioxide and the hydrogen gets oxidised to form water. Further when treated with lime water the carbon dioxide forms precipitate of calcium carbonate turning limewater milky. Also, the water formed when reacted with anhydrous copper sulphate forms hydrated copper sulphate.