Question

Calcium hydroxide $\text{(Ca(OH}{{\text{)}}_{2}}\text{)}$ in water is used for:
A. Whitewashing
B. Preparing ammonia, caustic soda and bleaching powder
C. Reducing the activities of the soil
D. All of the above purposes.

Answer 1

Hint: For this problem, we have to study the calcium hydroxide properties due to which we can determine the correct properties from the given option. We have to study both physical and chemical properties.

Complete Step-by-Step answer:
- In the given question, we have to choose one or more than one correct property of the calcium hydroxide from the given options.
- As we know that calcium hydroxide, an inorganic compound has another name that is slaked lime which is a powdery white substance.
- Other names of the compound include hydrated lime, pickling lime and caustic lime.
- The compound can be prepared easily by the reaction between sodium hydroxide and calcium hydroxide in water.
$\text{CaC}{{\text{l}}_{2}}\text{ + 2NaOH }\to \text{ Ca(OH}{{\text{)}}_{2}}\text{+ 2NaCl}$
- Calcium hydroxide is widely used in whitewashing. When calcium hydroxide comes in contact with the carbon dioxide it produces calcium carbonate which makes the wall shining.
- The chemical reaction of whitewashing is:
$\text{Ca(OH}{{\text{)}}_{2}}\text{+ C}{{\text{O}}_{2}}\text{ }\to \text{ CaC}{{\text{O}}_{3}}\ \text{+ }{{\text{H}}_{2}}\text{O}$
- Now, calcium hydroxide has another use also that is in the synthesis of ammonia. Caustic soda as well as bleaching powder.
- In ammonia, $\text{Ca(OH}{{\text{)}}_{2}}\text{+ 2N}{{\text{H}}_{4}}\text{Cl }\to \text{ CaC}{{\text{l}}_{2}}\text{ + 2N}{{\text{H}}_{3}}\ \text{+ 2}{{\text{H}}_{2}}\text{O}$ here along with the ammonia, calcium chloride and water are also produced.
 - In caustic soda, $N{{a}_{2}}C{{O}_{3}}\text{ + }Ca{{(OH)}_{2}}\,\to \text{ }CaC{{O}_{3}}\text{ + 2}NaOH$, sodium hydroxide is the molecular formula of caustic soda.
- For bleaching powder, $C{{l}_{2}}\text{ + }Ca{{(OH)}_{2}}\text{ }\to \text{ }CaOC{{l}_{2}}\text{ + }{{H}_{2}}O$ here $CaOC{{l}_{2}}$ is bleaching powder.
- Moreover, calcium hydroxide is used in the soil to increase the acidity of soil and maintain the proper soil structure.
- The addition of calcium hydroxide increases the alkaline nature of the soil and that's why it is used by farmers as agricultural lime.
Therefore, option D is the correct answer.

Note: Calcium hydroxide plays an important role in plant growth and its activity because it increases the ability of the plant to absorb nutrients. Also, calcium hydroxide along with water is sprayed on the soil to increase the soil pH to activate the sodium persulfate.