Which polymer is used in making bulletproof glass?
A. Polycarbonate
B. Bakelite
C. Polyethylene
D. PVC
Answer: Option A
Solution (By JKSSB Mock Tests)
Polycarbonate is a tough, transparent thermoplastic used in bulletproof glass, CDs, and lenses. Polyethylene is for bags; PVC for pipes; Bakelite is thermoset.
Explanation:
Zn + H₂SO₄ → ZnSO₄ + H₂↑. Hydrogen gas is released, which burns with a pop sound. This is a test for hydrogen. Metals above hydrogen in reactivity series displace it from acids. Dilute H₂SO₄ with Zn produces H₂; with Cu, no reaction.
Explanation:
Sodium is a soft alkali metal that can be easily cut with a knife, revealing a silvery surface that tarnishes quickly in air. Potassium is also soft. Iron, zinc, and copper are much harder. Alkali metals have low density and low melting points. They are stored under kerosene to prevent reaction with moisture and oxygen.
Explanation:
Atomic number is the number of protons, which is 17 for all chlorine atoms. Mass numbers differ due to different neutrons (18 and 20). Isotopes have same atomic number, different mass number.
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