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Chemistry

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Showing 826 to 850 of 1398 questions (page 34 of 56).

826. Aspirin is chemically

A. salicylic acid B. acetylsalicylic acid C. phenol D. methyl salicylate E. benzoic acid

827. The monomer of polyvinyl chloride is

A. chloroform B. propene C. vinyl chloride D. ethene E. styrene

828. Vulcanization of rubber involves heating it with

A. sulphur B. phosphorus C. chlorine D. carbon E. nitrogen

829. The building blocks of nucleic acids are

A. glycerols B. nucleotides C. monosaccharides D. amino acids E. fatty acids

830. Vitamins B and C are described as water soluble because they

A. are proteins B. are stored in fat tissue C. contain several polar hydroxyl and amino groups D. contain long hydrocarbon chains E. are minerals

831. The specificity of an enzyme is explained by the

A. band theory B. kinetic theory C. resonance theory D. lock and key model of the active site E. collision theory

832. Cracking of heavy petroleum fractions is carried out to

A. increase the molar mass B. increase the boiling point C. remove sulphur only D. form aromatics only E. obtain lighter and more useful hydrocarbons

833. The octane number of a fuel measures its

A. resistance to knocking B. volatility C. sulphur content D. density E. energy content

834. Biochemical oxygen demand is a measure of

A. the total dissolved solids B. the acidity of water C. the oxygen required by micro-organisms to decompose organic matter in water D. the chlorine content E. the hardness of water

835. Primary treatment of waste water consists mainly of

A. chlorination B. reverse osmosis C. biological oxidation D. physical removal of suspended solids by screening and sedimentation E. ion exchange

836. Photochemical smog is formed mainly from

A. nitrogen oxides and unburnt hydrocarbons in sunlight B. ammonia and dust C. carbon dioxide and water D. sulphur dioxide and soot E. chlorofluorocarbons

837. Two components can be separated by chromatography because they differ in

A. molar mass only B. density C. their relative affinity for the stationary and mobile phases D. colour E. melting point

838. Avogadro's law states that equal volumes of all gases under the same conditions contain

A. the same energy B. the same density C. equal masses D. equal numbers of molecules E. equal numbers of atoms

839. The number of moles present in 4.4 g of carbon dioxide is

A. 0.44 B. 0.01 C. 1.0 D. 0.2 E. 0.1

840. The percentage of oxygen by mass in water is about

A. 66.7% B. 88.9% C. 11.1% D. 33.3% E. 50%

841. The complete combustion of one mole of methane requires oxygen of amount

A. 1.5 mol B. 2 mol C. 1 mol D. 0.5 mol E. 3 mol

842. For solvent extraction to work, the two solvents used must be

A. both aqueous B. of the same density C. immiscible with each other D. miscible with each other E. chemically identical

843. A Buchner funnel with a filter flask is used for

A. titration B. distillation C. crystallization D. sublimation E. filtration under suction

844. The solution left after crystals have separated out during crystallization is called the

A. mother liquor B. distillate C. filtrate only D. eluent E. supernatant gas

845. In thin layer chromatography, the stationary phase is supported on

A. a filter funnel B. a metal wire C. a glass or plastic plate D. a strip of paper E. a column of solvent

846. A gas occupies 2 dm3 at 1 atm. At constant temperature and 4 atm its volume becomes

A. 4 dm3 B. 1 dm3 C. 8 dm3 D. 0.5 dm3 E. 2 dm3

847. A gas occupying 273 cm3 at 273 K is heated at constant pressure to 546 K. Its new volume is

A. 409 cm3 B. 273 cm3 C. 1092 cm3 D. 136 cm3 E. 546 cm3

848. Standard temperature and pressure are defined as

A. 0 K and zero pressure B. 273 K and 760 mm of mercury only at the equator C. 373 K and 1 atm D. 298 K and 1 atm E. 273.15 K and 1 atm

849. The volume occupied by 0.5 mol of any ideal gas at STP is

A. 5.6 dm3 B. 11.2 dm3 C. 2.24 dm3 D. 22.4 dm3 E. 44.8 dm3

850. A hydrogen bond is typically

A. weaker than a covalent bond but stronger than a London force B. stronger than a covalent bond C. of zero energy D. weaker than a London dispersion force E. identical to an ionic bond

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