Question

Water turns anhydrous copper sulphate solution in the carbon-hydrogen detection experiment:

A.brown
B.red
C.blue
D.green

Answer 1

Hint: We know that qualitative analysis helps in determining the component present in a given compound. Organic compounds composed of hydrogen, carbon, nitrogen, oxygen, sulphur, halogens etc. There are separate methods for qualitative analysis of all the elements of organic compounds.

Complete step by step answer:
Let’s discuss the qualitative analysis of carbon and hydrogen. The carbon and hydrogen is detected by reaction of the organic compound with CuO in a test tube (dry). The carbon gets oxidized to carbon dioxide and hydrogen gets oxidized to water. Then carbon dioxide and water are passed over anhydrous copper sulphate (white in colour) and then bubbled through lime water. The turning of white copper sulphate to blue is because of the formation of${\rm{CuS}}{{\rm{O}}_{\rm{4}}}.5{{\rm{H}}_{\rm{2}}}{\rm{O}}$. This indicates the presence of hydrogen in the compound. And if carbon dioxide turns lime water milky, the presence of carbon is confirmed. This is the experiment of detection of hydrogen and carbon in an organic compound. Therefore, we get to know that water transformed the colour of white anhydrous copper sulphate to blue.
Hence, the correct answer is option C.

Additional Information:
Liebig’s Combustion method is used to estimate Hydrogen and Carbon. In this method, a compound whose mass is known is heated with CuO. This chemical reaction results in oxidation of carbon to carbon dioxide and hydrogen to water. Then, carbon dioxide is absorbed in (KOH) potassium hydroxide solution and water is absorbed by anhydrous calcium chloride $\left( {{\rm{CaC}}{{\rm{l}}_{\rm{2}}}} \right)$ and then weighed.

Note:
Always remember that analytical chemistry deals with determining the chemical composition of the sample. There are two methods, qualitative and quantitative analysis. Quantitative analysis gives the quantity of a component in an organic compound.