Which of the following is a thermosetting plastic?
A. Nylon
B. Bakelite
C. PVC
D. Polythene
Answer: Option B
Solution (By JKExamLibrary)
Bakelite (phenol-formaldehyde resin) is thermosetting; once molded, it cannot be reshaped by heating. Polythene, nylon, PVC are thermoplastics, which can be repeatedly softened by heat.
Explanation:
Boyle's law: P ∝ 1/V at constant temperature and for a fixed mass (number of moles) of gas. If T or n changes, the simple inverse relationship does not hold.
Explanation:
Washing soda (Na₂CO₃) reacts with Ca²⁺ and Mg²⁺ ions in hard water to form insoluble carbonates: Ca²⁺ + Na₂CO₃ → CaCO₃↓ + 2Na⁺. Similarly MgCO₃. These precipitates are removed, softening the water. Ion exchange uses zeolites or resins. Boiling removes only temporary hardness. Distillation is expensive.
Explanation:
Oxygen (atomic number 8) has electronic configuration 2,6. It needs 2 more electrons to complete its octet. In water (H₂O), it shares two electrons (one each with two hydrogen atoms), forming two covalent bonds. Hence valency = 2. Oxidation number is -2.
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