Question

The balanced equation for the thermal dissociation of $C{O_2}$ gas is:
${\text{(A)}}\; 2C{O_2}\xrightarrow[{{{900}^0}C}]{{1{\text{ atm}}}}2CO + {O_2} \\\ {\text{(B)}}\;2C{O_2}\xrightarrow[{{{1300}^0}C}]{{1{\text{ atm}}}}2CO + {O_2} \\\ {\text{(C)}}\;2C{O_2}\xrightarrow[{{{1300}^0}C}]{{1{\text{ atm}}}}CO + {O_2} \\\ {\text{(D)}}\;C{O_2}\xrightarrow[{{{1300}^0}C}]{{1{\text{ atm}}}}C + {O_2} \\\$

Answer 1

thermal decomposition reactions are those reactions in which one reactant breaks down to give two or more products through the action of heat. The thermal decomposition reactions are endothermic. The above reaction needs to be balanced properly. For balancing the reactions check on both reactant and product side, it should have an equal number of atoms on both sides.

Complete answer:
Thermal decomposition is a type of decomposition reaction that requires heat to break down a single reactant into two or more products. These are endothermic reactions. Thermal decomposition reactions are activated by thermal energy. Thermal decomposition of $C{O_2}$ gives carbon monoxide and ${O_2}$ . It is a potential route for the utilization and consumption of $C{O_2}$ . The thermal decomposition of $C{O_2}$ takes place at a very high temperature of ${1300^0}C$ and a pressure of $1$ atm. When the reaction takes place, the breakdown of chemical bonds of $C{O_2}$ occurs which yields $CO$ and ${O_2}$ .
We are given above with some thermal decomposition of $C{O_2}$ and we have to write the balanced chemical reaction for it. If we observe the above options we can say that option A will not be the correct answer as here the reaction is taking place at ${900^0}C$ and we know from the above information that thermal decomposition of $C{O_2}$ occurs at ${1300^0}C$ so the first option is wrong. In option D the product is given as $C$ but we know that thermal decomposition of $C{O_2}$ gives $CO$ and ${O_2}$ hence option D is also wrong. Now we are left with option B and option C. for a balanced equation both sides should have equal atoms of $C$ and ${O_2}$ . In option C we see that the number of atoms of $C$ and ${O_2}$ is not equal. Hence option C is also wrong.
Therefore the balanced chemical equation for the thermal dissociation of $C{O_2}$ gas is:
${\text{(B)}}\;\;2C{O_2}\xrightarrow[{{{1300}^0}C}]{{1{\text{ atm}}}}2CO + {O_2}$
Thus the correct option is B.

Note:
There are two more types of decomposition reaction called electrolytic decomposition and photodecomposition. The decomposition reactions are very common reactions that occur everywhere around us. The most common example of a decomposition reaction is the digestion of food in our bodies. Here also complex molecules are broken down into smaller fragments. The question given above may be confusing because temperature and pressure are given but it only says to balance the reaction and identifying the correct temperature is important.