The main component of cement that is responsible for the initial setting is:
A. Tricalcium aluminate
B. Tetracalcium aluminoferrite
C. Dicalcium silicate
D. Tricalcium silicate
Answer: Option A
Solution (By JKExamLibrary)
Tricalcium aluminate (C₃A) reacts quickly with water and is responsible for the flash setting of cement. Gypsum is added to control the rate of this initial set. Tricalcium silicate (C₃S) provides early strength. Dicalcium silicate (C₂S) gives later strength. Tetracalcium aluminoferrite (C₄AF) contributes to color and hardness. Cement composition is abbreviated in cement chemistry notation.
Explanation:
In NO₂, each oxygen has valency 2; with two oxygens, total combining capacity = 4. Thus nitrogen's covalency is 4. The structure involves a coordinate bond. Oxidation state of N is +4. Valency is number of bonds formed: N forms two single bonds and one coordinate bond with O, total 4 bonds. In NO, valency is 2.
Explanation:
For silver electroplating, the electrolyte is typically a solution of silver cyanide (AgCN) in excess potassium cyanide or silver nitrate (AgNO₃). AgNO₃ with proper complexing agents can be used. CuSO₄ is for copper plating. NaCl is not suitable. The anode is pure silver, cathode is the article. Silver ions migrate to cathode and are reduced to metal.
Explanation:
The Ostwald process is the industrial method for manufacturing nitric acid (HNO₃). It involves the catalytic oxidation of ammonia (NH₃) to nitric oxide (NO), which is then further oxidized to nitrogen dioxide (NO₂) and absorbed in water to form concentrated nitric acid.
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