Question

Colloidal solutions of metals like gold can be prepared with their salt solutions to react with certain substances like $SnC{l_2}$, formaldehyde, phenyl hydrazine etc.
$2AuC{l_3} + 3SnC{l_2} \to 3SnC{l_4} + 2A{u_{sol}}$
The above method is an example of:
$1)$ Reduction method
$2)$ Oxidation Method
$3)$ Hydrolysis Method
$4)$ Double decomposition method

Answer 1

Colloidal solutions, also known as colloidal suspensions, are a mixture in which the compounds are suspended in a fluid in a regular pattern. A colloid is a very small particle that is consistently distributed throughout another substance. Colloidal systems can exist in all three phases of matter: gas, liquid, and solid.

Complete answer: The gain of electrons is referred to as a reduction reaction. In a chemical reaction, any substance that gains an electron is reduced.
A colloid is a heterogeneous system in which one component is scattered as very tiny particles in another substance known as the dispersion medium.
Colloidal solutions of metals such as gold can be created by reacting their salt solutions with certain chemicals such as $SnCl_2$, formaldehyde, and phenylhydrazine.
$2AuC{l_3} + 3SnC{l_2} \to 3SnC{l_4} + 2A{u_{sol}}$
Sn's oxidation state is shifting from $- 2$ to $- 4$. As a result, it is accumulating electrons, and hence the procedure is the reduction method.
Option $2$: This is not the correct option because in the oxidation reaction, the oxidation state of any metal increases whereas in the reaction given above, it is decreasing.
Option $3$: This is not the correct option because any chemical reaction in which a molecule of water breaks one or more chemical bonds is referred to as hydrolysis. The word refers to substitution, elimination, and solvation reactions in which water serves as the nucleophile. In this reaction, water is not used.
Option $4$: This is not correct option because double decomposition reaction is a type of decomposition reaction that occurs when two constituent reactants exchange positive and negative ions, resulting in the formation of two new compounds but in this reaction, Chlorine is adding to $SnC{l_2}$ and nothing is getting added to $Au$.
The correct option is 1.
Colloidal solutions of metals like gold can be prepared with their salt solutions to react with certain substances like $SnC{l_2}$, formaldehyde, phenyl hydrazine etc.
$2AuC{l_3} + 3SnC{l_2} \to 3SnC{l_4} + 2A{u_{sol}}$
The above method is an example of the Reduction method.

Note:
The reduction reaction is defined as the addition of hydrogen or a more electropositive element to a substance, or the removal of a more electronegative element or oxygen from a substance in other forms. In this type of reaction, the oxidation state decreases.