Question

A white coloured substance was placed in sunlight for some time. It was seen that it turned grey

after some time. Now answer the following questions:

(a) Why the white coloured substance turned grey?

(b) What is the role of sunlight during the reaction?

(c) Give the name and chemical formula of reactants and products in the reactions.​

Answer 1

Answer:

Silver chloride

White substance X on exposure to sunlight turns grey name the substance x and grey product. The substance X is silver chloride.

(A) The substance X is silver chloride. When silver chloride is kept in sun, it decomposes to form chlorine gas and silver. As the reaction proceeds, the white coloured substance turns grey in colour because of the formation of silver metal.

(B) A chemical reaction initiated by absorbing of energy in the form of light. Molecules on absorption of energy (photon) goes into transient state and available to decompose.

Let's Understand with an example,

2AgCl (Sunlight)→2Ag + Cl2

Silver Chloride (AgCl) absorbs energy in the form of light and decompose into Silver (Ag) and Chlroine gas (Cl2).

So, Sunlight provides energy to the molecules and help into going transient state and hence available for decomposition Reaction.

(C) The substance(s) to the left of the arrow in a chemical equation are called reactants. A reactant is a substance that is present at the start of a chemical reaction. The substance(s) to the right of the arrow are called products . A product is a substance that is present at the end of a chemical reaction.

Answer 2

Answer:

White coloured substance is Silver Chloride.

Explanation:

(a) When exposed to sunshine, white silver chloride turns grey.  This is because Silver chloride decomposes into silver and chlorine when exposed to light.

(b). To break down the reactants, decomposition processes require energy in the form of heat, light, or electricity. The sunlight aids in the decomposition of the reactants.

(c). Reactants:  $2 \mathrm{AgCl}(\mathrm{s}) \ and\ Sunlight$

     Products:$2 \mathrm{Ag}(\mathrm{s})+\mathrm{Cl}_{2}(\mathrm{~g})$

$2 \mathrm{AgCl}(\mathrm{s}) \text { (in presence of Sunlight) } \rightarrow 2 \mathrm{Ag}(\mathrm{s})+\mathrm{Cl}_{2}(\mathrm{~g})$

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