Question

The substance used for coagulating rubber from latex is:
(A) Ethanol
(B) Ethanoic acid
(C) Both
(D) None of these

Answer 1

Hint: Coagulation is the phenomenon of the precipitation of a colloidal solution when we add an excessive amount of an electrolyte to the solution. Small amounts of correct electrolytes are essential for the stability of the colloids.

Complete step by step answer:
Coagulation value is inversely proportional to the coagulating power of the ion.
$Coagulation\,\,value\,\alpha \dfrac{1}{{Coagulating\,Power}}$
- Different electrolytes have different coagulation capacity or flocculation value. Coagulation value is defined as the minimum concentration required of an electrolyte to cause the coagulation or flocculation of a solution.
- The Hardy Scruz rule states that greater the valency of flocculating ions, greater will be the coagulating power of that ion.
- Latex is a rubber fluid that is obtained from trees. Each rubber particle is composed of rubber polymers protected by a protein membrane layer.
- Negative charges are present on the surface of the membrane, which makes each rubber particle negatively charged. These particles repel each other which prevents them from combining and coagulating.
- $C{H_3}COOH$ is an organic acid. It gets Ionized in water and produces hydrogen ions. The positive charge on hydrogen ions helps to neutralise the negative charge present on the rubber particles thus allowing the latex to coagulate.
- When the neutral particles collide with each other, the outer membrane layers break up and the rubber polymers are set free.
Hence, Ethanoic acid is used for coagulating rubber from latex.

Therefore, Option (B) is correct.

Note:
 Coagulation value depends on the valency of the active ion known as flocculating ion, which is the ion that carries a charge opposite to the charge present on the colloidal particles. The unit of flocculation value is millimole per litre.