Vulcanization is the process of heating natural rubber with sulphur (usually at 100-140°C) to improve its properties. Sulphur forms cross-links (disulfide bridges) between the polymer chains, making the rubber harder, more elastic, and less sensitive to temperature changes.
Explanation:
Cobalt-60 emits gamma rays used in radiotherapy to destroy cancerous cells. Carbon-12 and sodium-23 are stable. Phosphorus-32 is radioactive but used as tracer, not for cancer therapy.
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:
Hydrogen chloride is a polar covalent bond because the shared electron pair is unequally shared due to the higher electronegativity of chlorine (3.0) compared to hydrogen (2.1). The bond has a dipole moment, making HCl molecule polar. In water, HCl ionizes to H⁺ and Cl⁻, but the gaseous molecule is covalent. Pure ionic bonds exist in compounds like NaCl where electronegativity difference is large (>1.7).
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