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2276. A compound contains 40% carbon, 6.7% hydrogen and 53.3% oxygen by mass. Its empirical formula is

A. CH2O B. CH4O C. C2H6O D. C2H4O2 E. CHO

2277. The number of moles in 9.8 g of sulphuric acid is

A. 0.05 B. 0.1 C. 1.0 D. 0.98 E. 0.2

2278. The number of molecules in 11.2 dm3 of oxygen gas at STP is

A. 1.204 x 10^24 B. 6.02 x 10^23 C. 1.5 x 10^23 D. 3.01 x 10^23 E. 6.02 x 10^22

2279. Isotopes of an element are separated on the basis of

A. difference in charge only B. chemical reactivity C. boiling point of the compound D. difference in colour E. difference in mass

2280. A fluted filter paper is used in filtration to

A. increase the surface area available for filtration B. neutralize the filtrate C. remove coloured impurities D. reduce the pore size E. dry the precipitate

2281. Which pair of substances can be purified by sublimation?

A. copper sulphate and alum B. glucose and urea C. iodine and naphthalene D. ethanol and water E. sodium chloride and sugar

2282. In paper chromatography, the Rf value of a component is always

A. greater than 1 B. equal to 1 C. independent of the solvent D. negative E. less than or equal to 1

2283. Solvent extraction is governed by the

A. law of mass action B. law of definite proportions C. Raoult's law D. distribution law E. Hess's law

2284. A good solvent for crystallization should

A. dissolve the impurities only when cold B. dissolve the solute more when hot than when cold C. have a very high boiling point only D. dissolve the solute equally well hot and cold E. react with the solute

2285. Boyle's law states that at constant temperature the volume of a given mass of gas is

A. independent of pressure B. directly proportional to pressure C. inversely proportional to pressure D. proportional to temperature E. proportional to the square of pressure

2286. Extrapolation of the volume against temperature graph for a gas gives absolute zero at

A. -273.16 degrees Celsius B. 100 degrees Celsius C. -100 degrees Celsius D. 0 degrees Celsius E. -373 degrees Celsius

2287. The value of the gas constant R in dm3 atm mol-1 K-1 is

A. 8.314 B. 0.083 C. 0.0821 D. 1.987 E. 62.4

2288. According to Graham's law, the rate of diffusion of a gas is

A. proportional to the square of its molar mass B. independent of molar mass C. proportional to its molar mass D. inversely proportional to the square root of its molar mass E. proportional to the square root of its molar mass

2289. In the van der Waals equation, the constant b accounts for

A. the volume occupied by the gas molecules B. the number of moles C. intermolecular attraction D. the kinetic energy of the molecules E. the temperature correction

2290. A gas cannot be liquefied by pressure alone above its

A. transition temperature B. critical temperature C. melting point D. inversion temperature E. boiling point

2291. The average kinetic energy of gas molecules is directly proportional to

A. pressure B. volume C. molar mass D. density E. absolute temperature

2292. Dalton's law of partial pressures does not apply to gases that

A. are at high temperature B. are monatomic C. have different molar masses D. react chemically with each other E. are at low pressure

2293. The abnormally high boiling point of water compared with hydrogen sulphide is due to

A. London dispersion forces B. hydrogen bonding C. its ionic character D. covalent network bonding E. its low molar mass

2294. The boiling point of a liquid at reduced external pressure

A. decreases B. becomes zero C. doubles D. increases E. remains unchanged

2295. The coordination number of each ion in a sodium chloride crystal is

A. 12 B. 8 C. 2 D. 4 E. 6

2296. The existence of a substance in more than one crystalline form is called

A. allotropy in solutions only B. anisotropy C. polymorphism D. isomorphism E. isotopy

2297. Which type of solid has the highest melting point?

A. amorphous B. metallic C. covalent network D. ionic E. molecular

2298. The maximum number of electrons that can occupy the shell with n = 3 is

A. 10 B. 6 C. 8 D. 32 E. 18

2299. For an electron in a 3d orbital, the azimuthal quantum number l is

A. 2 B. 3 C. 1 E. 4

2300. The ground state electronic configuration of chromium (Z = 24) is

A. [Ar] 4s2 4p4 B. [Ar] 3d5 4s1 C. [Ar] 3d6 D. [Ar] 3d3 4s3 E. [Ar] 3d4 4s2

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