Question

Assertion: In a chemical reaction, the total mass of the products remains same as the total mass of the reactants.

Reason: A chemical reaction involves simply the exchange of atoms and no new species are formed.

• A. If both assertion and reason are correct and the reason is the correct explanation for assertion.
• B. If both assertion and reason are correct but the reason is not the correct explanation for assertion.
• C. If the assertion is correct but the reason is incorrect.
• D. If the assertion is incorrect but the reason is correct.

Answer 1

The correct option is C

If the assertion is correct but the reason is incorrect.

The explanation for the correct option:

(C) If the assertion is correct but the reason is incorrect.

The explanation for the assertion.

Law of conservation of mass

1. By the law of conservation of mass, the total mass of a system remains constant throughout the reaction.
2. The mass of the reactants before the reaction is the same as the mass of the products after the reaction has been completed.

Hence, the assertion is correct.

The explanation for the reason statement.

1. In a chemical reaction, new species are formed from the rearrangement of atoms from the original substance.

Hence, the reason statement is incorrect.

The correct reason

A chemical reaction is always associated with the formation of new species (the products) that are different from the initial species (the reactants) involved in the reaction.

For example - The reaction of hydrogen $\left({\mathrm{H}}_2\right)$ and oxygen $\left({\mathrm{O}}_2\right)$ gas produces water $\left({\mathrm{H}}_2\mathrm{O}\right)$ which is an entirely new species that is different from both hydrogen and oxygen.

${\mathrm{H}}_2\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to {\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

Hence, (C) is the correct option.