Question

assertion: all chemical reactions are accompanied by changes in energy.
Reason: energy is always required to drive a chemical reaction.
A. Both assertion and reason are correct and reason is the correct explanation for assertion
B. Both assertion and reason are correct but reason is not the correct explanation for assertion
C. Assertion is correct but reason is incorrect
D. Assertion in incorrect but reason is correct

Answer 1

Hint: Chemical reaction is a process in which two or more reactants combine at required temperature and pressure to give one or more corresponding products.
Chemical reactions in general involve breakage of bonds in order to form new bonds, so the energy of reactant and products could differ depending whether it is exothermic or endothermic reaction.

Complete step by step answer:
Chemical reaction is chemical change in which one or more different compounds are converted into new products .The product formed may be an element or a compound. In chemical reactions the formation of new products is because of the different arrangement of reactant atoms.
reactant $\to$ product
For example rusting of iron , combustion , electrochemical reaction etc .some reaction are slow some are fast , to increase the rate of reaction there are some methods used such as by increasing the temperature in which reaction taking place and adding of catalyst to reaction to increase the rate of reaction by decreasing the rate of reaction .some energy give out energy , these are exothermic which means energy or heat is released during the reaction and other one is endothermic in which heat is required to carry out the reaction .
Now, coming to the solution part during a chemical reaction energy change may be exothermic or endothermic . when energy is released during the reaction temperature should decrease and when energy is needed during the reaction temperature should increase .
Hence there is no always a requirement of energy to drive the chemical reaction .

So the correct option is C, assertion is correct but reason given is incorrect.

Note: In a chemical reaction changes in energy of the reactant and products takes place, and some of the energy is released in cases of exothermic reaction. While in case of endothermic reaction, the energy is absorbed by the product, and so it is incorrect to generalise the changes in energy as it is not always required, sometimes it is given out too.