The incorrect statement about rubber is:

Rubber particles are positively charged

The correct answer is option 3. Rubber particles are positively charged.

Let us examine each statement about rubber in detail to understand why one of them is incorrect.

Latex is a milky fluid found in many plants, including the rubber tree (Hevea brasiliensis). It is a colloidal suspension in which rubber particles are dispersed in water. The rubber particles in latex are small and dispersed in water, along with proteins, resins, and other substances.

Analyzing the Statements:

Statement 1: Latex is a colloidal solution of rubber particles

A colloid is a mixture where very small particles of one substance are evenly distributed throughout another substance. In the case of latex, rubber particles are dispersed in water, forming a colloidal solution. This statement is correct. Latex is indeed a colloidal solution of rubber particles in water.

Statement 2: Rubber particles are negatively charged

In natural latex, rubber particles typically carry a negative charge. This negative charge is crucial for maintaining the stability of the colloidal solution. The negative charges on the rubber particles repel each other, preventing the particles from coming together and coagulating prematurely. This statement is correct. Rubber particles in natural latex are negatively charged.

Statement 3: Rubber particles are positively charged

As discussed earlier, in natural latex, the rubber particles are not positively charged but negatively charged. The negative charge helps keep the latex stable by preventing the rubber particles from clumping together. This statement is incorrect. Rubber particles are not positively charged; they are negatively charged.

Statement 4: Rubber is obtained by coagulation of latex

Coagulation is the process of converting the colloidal solution of latex into solid rubber. This is typically done by adding an acid, like acetic acid, to the latex. The acid neutralizes the charges on the rubber particles, causing them to clump together and form solid rubber. This statement is correct. Rubber is indeed obtained by coagulating latex.

Latex is a colloidal solution where rubber particles are dispersed in water. These rubber particles are negatively charged in natural latex, which helps maintain the stability of the colloid. Rubber is extracted from latex by a process called coagulation, where the particles lose their charge and clump together to form solid rubber.

The incorrect statement is "Rubber particles are positively charged" because, in reality, they are negatively charged in natural latex.