Plaster of Paris should be stored in a moisture-proof container because:
A. It reacts with moisture to form a hard solid (gypsum)
B. It sublimes
C. It dissolves in water
D. It evaporates
Answer: Option A
Solution (By JKExamLibrary)
CaSO₄·½H₂O readily absorbs moisture to set to CaSO₄·2H₂O (gypsum), becoming hard and useless for molding. So it must be kept dry. Reaction: CaSO₄·½H₂O + 1½H₂O → CaSO₄·2H₂O.
Explanation:
Destructive distillation is the process of heating a carbon-containing substance (like coal or wood) in the absence of air to break it down into various products. For coal, it yields coke, coal tar, coal gas, and coal dust. Fractional distillation is used for separating liquid mixtures like petroleum.
Explanation:
Bayer's process uses hot NaOH to dissolve alumina from bauxite, leaving behind insoluble impurities (red mud). Alumina is then precipitated. Hall-Héroult is electrolytic reduction of alumina to aluminium.
Explanation:
According to the reactivity series, zinc is more reactive than copper, so Zn displaces Cu: Zn + CuSO₄ → ZnSO₄ + Cu. Silver, gold, and mercury are less reactive than copper and cannot displace it. Reactivity: K > Na > Ca > Mg > Al > Zn > Fe > Pb > Cu > Ag > Au. Displacement reactions are used in metallurgy and galvanic cells. The blue color of CuSO₄ fades as copper is deposited.
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