The drying agent which absorbs carbon dioxide and reacts violently with water is:
A.Sodium carbonate
B.Alcohol
C.Conc. sulphuric acid
D.Calcium oxide

Hint: Drying agents can be defined as any hygroscopic substance that induces or sustains a state of dryness in its vicinity. strong bases such as soda-lime, sodium hydroxide, potassium hydroxide, and lithium hydroxide can remove carbon dioxide by chemically reacting with it.

Complete step by step answer:
The common drying agents are anhydrous inorganic salts that acquire waters of hydration when exposed to moist air or a wet solution.
Now let’s analyze each of the options systematically:
Sodium Carbonate does not react with $C{O_2}$ and also is not used as a dehydrating agent. Hence this option is wrong and can be eliminated
Alcohol does not react with $C{O_2}$ and also is not used as a dehydrating agent. Hence this option is wrong and can be eliminated
Conc. Sulphuric acid is a very good dehydrating agent and has a strong affinity for water but it does not absorb carbon dioxide. Hence this option is wrong and can be eliminated
Out of the given options, only ${\text{CaO}}$ that is calcium oxide:
- reacts with $C{O_2}$ to form calcium carbonate $CaO + C{O_2} \to CaC{O_3}$
-Calcium oxide acts as a drying agent \[{\text{CaO + }}{{\text{H}}_{\text{2}}}{\text{O}} \to {\text{Ca(OH}}{{\text{)}}_{\text{2}}}\]

Therefore, we can conclude that the correct answer to this question is option D.

Note:
Important drying agents include anhydrous sodium sulfate, magnesium sulfate, or calcium chloride. These drying agents when added to a solution of any compound pick up any extra water from the compound solution and become hydrated. The hydrated salt now clumps and further can be filtered out or left behind during decanting.