The rate of effusion of two gases A and B are in the ratio 1:2. If molar mass of A is 64 g/mol, molar mass of B is:
A. 16 g/mol
B. 128 g/mol
C. 32 g/mol
D. 256 g/mol
Answer: Option A
Solution (By JKSSB Mock Tests)
Graham's law: r₁/r₂ = √(M₂/M₁). Given rA/rB = 1/2, so √(MB/MA) = 1/2. Squaring: MB/MA = 1/4 => MB = MA/4 = 64/4 = 16 g/mol. B is lighter and diffuses faster. Logical check: rate inversely proportional to square root of molar mass; if rate is double, mass is quarter. Answer is 16.
Explanation:
Graphite's layered structure with weak van der Waals forces between layers allows them to slide over each other, making it a good dry lubricant. It is used in machines where oil cannot be used (high temperature) or in pencil lead mixed with clay. Diamond is hard, used as abrasive. Fullerenes are nanomaterials, not lubricants. Coal is fuel.
Explanation:
Sodium hydroxide (NaOH) has ionic bond between Na⁺ and OH⁻, and covalent bond between O and H within OH⁻. NaCl is purely ionic; CH₄ and HCl are purely covalent (polar covalent in HCl, but not ionic).
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