Which of the following statements about diamond is true?
A. It is the hardest natural substance
B. It is a good lubricant
C. It conducts electricity
D. It has a layered structure
Answer: Option A
Solution (By JKSSB Mock Tests)
Diamond has a rigid 3D covalent network, making it the hardest natural material. It does not conduct electricity (no free electrons). It is not layered (graphite is). It is used as an abrasive, not a lubricant.
Explanation:
Cation exchange resins contain Na⁺ ions which are replaced by Ca²⁺/Mg²⁺, softening the water. Anion exchange can also be used for deionization. Washing soda precipitates Ca/Mg.
Explanation:
Atomic radius increases down a group as the number of shells increases. Iodine (I) is in Period 5, below F (2), Cl (3), Br (4). Thus iodine has the largest atomic radius among these halogens.
Explanation:
Across period 3, ionization energy increases from Na to Ar. Chlorine has high ionization energy due to high effective nuclear charge and small atomic radius, though Argon is highest. Among these, Cl has highest IE.
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