Question

How do the following help in bringing about a chemical change?

i. Light ii. Pressure iii. Heat iv. Catalyst​

Answer 1

Answer:

a)Some chemical reactions can take place in the presence of light. Ex. Photosynthesis.

b)Some chemical reactions take place when reactants are subjected to high pressure. e.g: Nitrogen and hydrogen when subjected to high pressure produce ammonia gas.

c)Some chemical reactions take place only in the presence of heat. e.g. When lead nitrate is heated, it breaks into lead monoxide, nitrogen dioxide, and oxygen.

d)1. Positive catalyst: When a catalyst increases the rate of reaction finely divided iron is used as a positive catalyst in the manufacturing of ammonia from hydrogen and nitrogen.

2. Negative Catalyst: When a catalyst decreases the rate of reaction.

Ex. Phosphoric acid act as a negative catalyst to decrease the rate of the decomposition of hydrogen peroxide.

Answer 2

Answer:

I) Because of light the colour of chemical depends

ii) Pressure of putting a chemical decides it's dilution percent

iii) Heat is also responsible for chemical change to increase the temperature of reaction

iv) Catalyst changes the speed of reaction.

Explanation:

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