The setting time of cement is controlled by adding: MCQ with Answer and Explanation

The setting time of cement is controlled by adding:
A. Limestone
B. Clay
C. Sand
D. Gypsum
Answer: Option D
Solution (By JKSSB Mock Tests)
Gypsum (CaSO₄·2H₂O) is added to clinker to slow down the rapid setting of C₃A, providing workable time. Without gypsum, flash set occurs.

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Practice More chemistry Questions

Question #1
Graphite is used as an electrode because it:
A. Is very hard
B. Is transparent
C. Has free electrons and is chemically inert
D. Is an insulator

Correct Answer: Option C


Explanation:
Graphite conducts electricity due to delocalized electrons in its structure and is chemically inert, allowing its use in electrodes for electrolysis and batteries. Diamond is an insulator. Hardness is not the reason; graphite is soft. It is opaque and black. Graphite electrodes are used in arc furnaces.

This question belongs to: Science chemistry
Question #2
The reaction N₂ + 3H₂ → 2NH₃ is an example of:
A. Combination reaction
B. Displacement reaction
C. Double displacement reaction
D. Decomposition reaction

Correct Answer: Option A


Explanation:
Two or more substances combine to form a single product: N₂ + 3H₂ → 2NH₃. This is a combination (synthesis) reaction. Decomposition involves a single compound breaking down. Displacement: one element displaces another. Double displacement: exchange of ions. The Haber process for ammonia is also a redox and reversible reaction. Combination can be exothermic.

This question belongs to: Science chemistry
Question #3
The chemical name of washing soda is:
A. Sodium hydroxide
B. Sodium chloride
C. Sodium carbonate decahydrate
D. Sodium bicarbonate

Correct Answer: Option C


Explanation:
Washing soda is sodium carbonate decahydrate, with the chemical formula Na₂CO₃·10H₂O. Sodium bicarbonate is baking soda (NaHCO₃). Sodium hydroxide is caustic soda (NaOH), and sodium chloride is common table salt (NaCl). Washing soda is used for cleaning and water softening.

This question belongs to: Science chemistry