Q13 of 53 Page 125

By adding gypsum to cement

Gypsum is CaSO4.2H2O. Gypsum is added in 2-3% of weight to cement along with CaO (lime) and clay. Gypsum is added in order to increase the setting time of cement. Slowing the setting time of cement makes it harden sufficiently. The correct answer is (ii).

More from this chapter

All 53 →
11

In the synthesis of sodium carbonate, the recovery of ammonia is done by treating NH4Cl with Ca(OH)2. The by-product obtained in this process is

 12

When sodium is dissolved in liquid ammonia, a solution of deep blue colour is obtained. The colour of the solution is due to

 14

Dead burnt plaster is

 15

Suspension of slaked lime in water is known as