The addition of gypsum to cement clinker during grinding:
A. Increases color
B. Decreases setting time
C. Increases setting time
D. Decreases strength
Answer: Option C
Solution (By JKExamLibrary)
Gypsum (CaSO₄·2H₂O) is added to clinker to control the rapid reaction of tricalcium aluminate with water, which would otherwise cause flash (quick) setting. Gypsum slows down the hydration of C₃A, thus increasing the setting time and allowing workability. Without gypsum, cement would set almost immediately upon mixing with water, making placement impossible.
Explanation:
Mg goes from 0 to +2 oxidation state, losing electrons – oxidized. Oxygen is reduced (0 to -2). This is a combustion/combination redox reaction.
Explanation:
Aluminium displaces iron from iron(III) oxide because Al is more reactive. This is a single displacement (or thermite) reaction. Also redox: Al oxidized, Fe reduced. Combination: one product; decomposition: one reactant.
Explanation:
James Chadwick discovered the neutron in 1932 by bombarding beryllium with alpha particles, producing a neutral radiation that he identified as neutrons. Rutherford had predicted the existence of a neutral particle in 1920. Chadwick's discovery explained isotopes' mass differences. Neutron: mass ≈ 1.00866 u, no charge. It is stable inside the nucleus but decays (half-life ~10 min) when free.
No comments yet. Be the first to start the discussion!