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Showing 851 to 875 of 3046 questions (page 35 of 122).

851. The energy released in nuclear reactions arises from

A. ionization B. electron transitions C. chemical bonding D. mass defect E. frictional heating

852. Energy production in the Sun is mainly due to

A. nuclear fission B. chemical combustion C. nuclear fusion D. radioactive decay of uranium E. gravitational contraction alone

853. Which radiation has the greatest penetrating power?

A. beta B. gamma C. neutron in air only D. alpha E. proton

854. In a nuclear reactor, the moderator is used to

A. slow down fast neutrons B. control the coolant flow C. shield the operators D. increase the fuel temperature E. absorb excess neutrons

855. The value of Avogadro's number is

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

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

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

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

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

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

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

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

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

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

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

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

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

862. A fluted filter paper is used in filtration to

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

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

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

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

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

865. Solvent extraction is governed by the

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

866. A good solvent for crystallization should

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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