Question

The initial weight of candle $ = x{{ gm}}$, the Final weight of the candle after burning $ = y{{ gm}}$
Which of the following options is correct?
A. x $ < $ y
B. x $ > $ y
C. x $ = $ y
D. None of the above

Answer 1

Hint: Candle gains weight while burning because of oxidation. When a candle is burnt the mass of the products is greater than the mass of the original candle wax. Hence, there is a gain in weight when the candle is burnt in the air.

Complete step by step answer:
We know that when a candle is lighted, the wax that is present near the wick will melt. Wick absorbs the liquid wax. The liquid wax gets evaporated because of the heat produced by the flame.
The gain in mass when the candle is burnt in the air is due to the mass of atmospheric oxygen which combines with the carbon and hydrogen of the candle wax during burning to produce water vapor and carbon dioxide.
Burning is a chemical change that includes the process of oxidation by which it produces heat and light. When a candle is burnt in air, the weight or the mass of the product is increased due to atmospheric oxygen which combines with the carbon and hydrogen of the candle wax during burning. It burns to supply water vapor and $C{O_2}$. And this an irreversible change. Here, the chemical reaction of a burning candle is:
${C_x}{H_y} + (x + \dfrac{y}{4}){O_2} \to \dfrac{y}{2}{H_2}O + xC{O_2}$
Here, $x = n$, $y = 2n + 2$.
From the above explanation, we can say that formation of new products (carbon dioxide and water) takes place, by the addition of oxygen mass of the product will increase and the original properties of wax will change.

So, the correct answer is Option A.

Note: The law of conservation of mass tells us the matter is neither created nor destroyed during a chemical reaction. It is possible to rearrange the atoms to form a new compound, but the total mass of the system remains the same or remains constant.