Chemistry

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Showing 976 to 1000 of 1398 questions (page 40 of 56).

976. The sequence of amino acids in a polypeptide chain constitutes the

A. active site only B. quaternary structure C. tertiary structure D. secondary structure E. primary structure of the protein

977. The monomer of natural rubber is

A. isoprene B. butadiene C. styrene D. ethene E. vinyl chloride

978. A thermosetting plastic differs from a thermoplastic in that it

A. dissolves in water B. softens repeatedly on heating C. conducts electricity D. sets permanently on heating because of cross linking E. is always transparent

979. Lipids are hydrolysed by alkali to give glycerol and

A. nucleotides B. amino acids C. salts of fatty acids D. alcohols only E. monosaccharides

980. Ozone depletion is most severe over

A. the equator B. northern Europe C. the Sahara D. the Pacific Ocean E. Antarctica

981. Solid waste disposal by sanitary landfill requires lining of the site chiefly to

A. improve appearance B. increase the temperature C. prevent leachate from contaminating groundwater D. speed up decay E. allow gas to escape

982. The value of Avogadro's number is

A. 3.01 x 10^23 B. 1.66 x 10^-24 C. 6.02 x 10^23 D. 6.02 x 10^24 E. 6.02 x 10^22

983. The molar volume of an ideal gas at standard temperature and pressure is

A. 1 dm3 B. 11.2 dm3 C. 24 dm3 D. 22.414 dm3 E. 44.8 dm3

984. The reactant that is completely consumed first and therefore limits the amount of product is called the

A. catalyst B. limiting reactant C. excess reactant D. intermediate E. spectator species

985. 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

986. 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

987. 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

988. 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

989. 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

990. 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

991. 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

992. 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

993. 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

994. 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

995. 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

996. 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

997. 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

998. 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

999. 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

1000. The average kinetic energy of gas molecules is directly proportional to

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

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