Chemistry

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Showing 851 to 875 of 1398 questions (page 35 of 56).

851. Ice floats on water because

A. ice is amorphous B. it contains dissolved air only C. hydrogen bonding gives ice an open structure of lower density D. it is warmer E. water is denser at 0 degrees Celsius than at 4 degrees Celsius

852. Molecular solids are generally

A. ionic in character B. good conductors of electricity C. soft with low melting points D. network covalent E. hard with high melting points

853. Ionic solids conduct electricity

A. only when molten or dissolved B. never C. only at absolute zero D. only as vapours E. in the solid state

854. Cleavage of a crystal along definite planes shows that

A. the crystal is anisotropic in colour only B. the crystal is ionic C. the crystal is amorphous D. the particles are arranged in an ordered pattern E. the crystal contains water

855. The three isotopes of hydrogen are

A. ortho, meta and para hydrogen B. protium, deuterium and tritium C. hydrogen, helium and lithium D. hydride, proton and hydronium E. alpha, beta and gamma hydrogen

856. The maximum number of electrons that a d subshell can hold is

A. 10 B. 18 C. 14 D. 6 E. 2

857. The wave mechanical model of the atom is based on the equation formulated by

A. Chadwick B. Bohr C. Schrodinger D. Rutherford E. Planck

858. The existence of discrete spectral lines rather than a continuous spectrum shows that atomic energy is

A. independent of the electron B. quantized C. infinite D. zero E. continuous

859. The number of lone pairs on the oxygen atom in a water molecule is

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

860. The shape of the phosphorus pentachloride molecule is

A. see saw B. tetrahedral C. trigonal bipyramidal D. octahedral E. square planar

861. The number of sigma bonds in an ethyne molecule is

A. 1 B. 3 C. 4 D. 5 E. 2

862. The number of pi bonds in a benzene molecule, on the Kekule representation, is

A. 3 B. 2 D. 1 E. 6

863. The specific heat capacity of water is about

A. 1.0 J g-1 K-1 B. 4.18 J g-1 K-1 C. 336 J g-1 K-1 D. 2.09 J g-1 K-1 E. 8.314 J g-1 K-1

864. The dissolution of ammonium chloride in water lowers the temperature, so the process is

A. endothermic B. adiabatic C. isothermal D. exothermic E. spontaneous only above 100 degrees Celsius

865. The imaginary surface separating a system from its surroundings is called the

A. phase B. interface C. medium D. meniscus E. boundary

866. Enthalpy changes of reaction are normally quoted in

A. kJ K-1 B. J K-1 mol-1 C. kJ mol-1 D. J E. mol kJ-1

867. The enthalpy of formation of a compound can be found from enthalpies of combustion using

A. Graham's law B. Le Chatelier's principle C. Raoult's law D. Hess's law E. Dalton's law

868. Chemical equilibrium is described as dynamic because

A. the catalyst is consumed B. the concentrations keep changing C. the reaction has stopped D. both forward and reverse reactions continue at equal rates E. the temperature keeps changing

869. The pH of a 0.01 mol dm-3 solution of sodium hydroxide at 25 degrees Celsius is

A. 12 B. 10 C. 7 D. 2 E. 14

870. Phenolphthalein is a suitable indicator for the titration of

A. a strong acid with a strong acid B. a weak acid with a strong base C. a strong acid with a weak base D. a weak acid with a weak base E. two neutral solutions

871. The volume of 0.1 mol dm-3 hydrochloric acid needed to neutralize 25 cm3 of 0.1 mol dm-3 sodium hydroxide is

A. 50 cm3 B. 2.5 cm3 C. 100 cm3 D. 25 cm3 E. 12.5 cm3

872. A concentration of one part per million corresponds to

A. 1 g of solute in 1 kg of solution B. 1 mg of solute in 1 kg of solution C. 1 mol of solute in 10^6 dm3 D. 1 g of solute in 1 g of solution E. 1 cm3 of solute in 1 dm3

873. Dissolving 0.5 mol of a solute in 500 g of solvent gives a molality of

A. 5 m B. 0.25 m C. 0.5 m D. 2 m E. 1 m

874. The mass of sodium hydroxide required to prepare 1 dm3 of a 0.5 mol dm-3 solution is

A. 5 g B. 40 g C. 20 g D. 10 g E. 80 g

875. Colligative properties are used experimentally to determine the

A. boiling point of the solvent only B. density of the solvent C. molar mass of a solute D. colour of a solute E. viscosity of the solution

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