Question

When a burning candle is covered with a glass it extinguishes because:
A.) supply of oxygen is cut off
B.) supply of hydrogen is cut off
C.) supply of nitrogen is cut off
D.) supply of $C{O}_2$ is cut off

Answer 1

Hint: While the burning of a candle, to keep burning the candle a continuous supply of the oxygen gas present in the air is needed but when we put a glass on the candle then it extinguishes.

Complete step by step answer:
A candle is an ignitable substance which provides light. For the burning of a candle, a heat source (such as a flame from a match stick or lighter) is required to light the wick of the candle. The wick is the thread like substance that is present in the candle. When the candle lights, the wick of the candle melts and then it vaporizes some amount of the fuel that is the wax of the candle. The vaporized wax of the candle then combines with the oxygen that is present in the atmosphere which helps to ignite the candle and to form a continuous flame. Here the flame melts the fuel of the candle that is the wax and then this wax moves in upward direction with the help of the wick by the capillary action. Then the liquified wax finally vaporizes to burn within the candle flame.
As we see that for the burning of a candle, a continuous supply of oxygen gas from the air is needed which reacts with the vaporized wax and causes the candle to burn continuously until the wax ends. By covering the candle with a glass, we will limit the amount of oxygen inside the tumbler that is left for the candle to burn. The carbon in the wax reacts with the remaining oxygen during the combustion reaction and produces carbon dioxide and heat. When all the oxygen is used up by the candle, then it will stop burning and finally extinguishes the fire of the candle.

Hence, option A.) is the correct option.

Note: Remember that when we burn the candle then carbon dioxide is produced. This is because of the reaction of oxygen with the wax. When the oxygen ends then the carbon dioxide will extinguish the flame.