This compound is conventionally used for white washing of buildings. Which of the following statements is / are true about it.
1. It is obtained by treating quick lime with water.
2. It is produced when calcium carbide reacts with water.
3. It is one of the raw materials used for the manufacture of Portland cement.
4. It is called slaked lime and its chemical formula is Ca(OH)2.
Select the correct answer using the code given below:
Options
A1 and 4 only
B2, 3 and 4 only
C1, 2 and 4 only
D1, 2 and 3 only
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Correct Answer
C1, 2 and 4 only
Model Answer
The substance used for whitewashing is Calcium oxide (CaO) also called quicklime.
When calcium oxide is mixed with water, it makes a solution of calcium hydroxide Ca(OH)2 which is used for whitewashing.
CaO+H2O = Ca(OH)2
Hence, statement 1 is correct.
Calcium hydroxide is produced when calcium carbide reacts with water.
CaC2+ 2H2O = C2H2 + Ca(OH)2 .
Hence, statement 2 is correct.
Calcium hydroxide Ca(OH)2 is conventionally called Slaked lime and is used for the whitewashing of buildings. Hence, statement 4 is correct.
CaO in the dry state is used as one of the raw materials in Portland cement while Ca(OH)2 i.e., Calcium hydroxide is used in whitewashing. Hence, statement 3 is incorrect.
A cycle diagram of limestone CaCO3 heated to quicklime CaO, water added to give slaked lime Ca(OH)2, then carbonated back to limestone.
