Question

A balanced chemical equation is in accordance with which one of the following laws given?
(A) Law of conservation of energy
(B) Law of conservation of mass
(C) Law of constant proportion
(D) Law of multiple proportion
(E) None of these

Answer 1

To answer this question we should understand the laws mentioned above. In a balanced equation the number of an element in the reactant side should be equal to the number of the same elements in the product side.

Complete step by step answer:
In a chemical equation the substance that is left to the arrow is called reactant and the substance that is to the right of the arrow is called product.
- Option A is "Law of conservation of energy". The law of conservation of energy states that the energy can neither be created nor destroyed. Firstly, there is no job for energy in balancing chemical equations. In case of chemical reaction the energy released out by reactant, which is restored back after formation of product. Option A is the wrong answer.
- Option B is "Law of conservation of mass". The law of conservation of mass which states that the atoms are neither created nor destroyed. Applying the law of conservation of mass to a chemical, there is no atom destroyed from the reactant side nor created in the product, so the number of elements in the reactant is equal to the number of elements in the product. This is the theory behind balancing chemical equations. The law of conservation of mass attributes for balancing a chemical equation. Thus, option B is the correct answer.
- Option C is "Law of constant proportion". It states that a given compound always contains its component elements in fixed ratio and does not depend on its sources and method of preparation. Here the ratio means the amount of that particular element in grams per mole etc. This does not apply to balancing the chemical equation. Thus, option C is the wrong answer.
- Option D is "Law of multiple proportion". It states that if there are two elements from more than one compound between them, then the ratio of masses of the second element which combine with a fixed mass of the first element which combines with a fixed mass of the first element will always be a ratio of small whole numbers. Just from the statement we can figure out as in balancing we do not take ratio in first place. We compare the number of atoms of a particular element in reactant and in product. Make it equal if not equal. Thus, option D is the wrong answer. The correct answer is option “B” .

Note: Chemical equation is the representation of a chemical reaction where the reactants react to give products. In a balanced chemical equation the number of particular elements in a reactant should be equal to the number of elements in the product. The law of conservation of mass attributes for balancing a chemical equation.