Question

In a lime kiln, to get a higher yield of$C{{O}_{2}}$, the measure that can be taken is:
(A) To remove CaO
(B) To add more $CaC{{O}_{3}}$
(C) To maintain a high temperature
(D) To pump out $C{{O}_{2}}$.

Answer 1

To solve this question, we first need to know what is lime kiln. A kiln is a type of oven or an insulated chamber that is used to carry out processes at sufficient temperature. The heating of limestone or calcium carbonate at high temperatures in the absence of oxygen is done in a lime kiln.

Complete answer:
Now, the balanced chemical equation of the process taking place in the kiln is as follows.
$CaC{{O}_{3}}\xrightarrow{heat}CaO+C{{O}_{2}}$
The calcination (heating of a substance at a high temperature in the absence of oxygen) of calcium carbonate (limestone) produces calcium oxide (quick lime) along with carbon dioxide.
The reaction takes place at a temperature of 900${}^\circ C$ at which the partial pressure of the carbon dioxide gas is 1 atm.
Now, we know that, according to Le Chatelier's principle, when there is a disturbance in a dynamic equilibrium, like a change in temperature, concentration, or pressure, the equilibrium will push to counteract the change.
So, when the concentration of $C{{O}_{2}}$ is decreased in the lime kiln chamber, the equilibrium will be disturbed, which is balanced by the system by moving the reaction in a forward direction and which leads to an increase in production of $C{{O}_{2}}$.

Hence, to get a higher yield of $C{{O}_{2}}$ in a lime kiln, the measure that can be taken is option (D) to pump out $C{{O}_{2}}$.

Note:
It should be noted that the rate of the reaction of the lime kiln process can be increased with an increase in temperature. When the temperature of the system is 1000${}^\circ C$ at which the partial pressure of the carbon dioxide gas is 3.8 atm, the reaction proceeds quickly.
But at extremely high temperatures, "dead-burned" lime is produced which is unreactive. This is why extremely high temperatures are avoided.