Chemistry

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Showing 551 to 575 of 1398 questions (page 23 of 56).

551. Standard temperature and pressure are defined as

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

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

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

553. A hydrogen bond is typically

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

554. Ice floats on water because

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

555. Molecular solids are generally

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

556. Ionic solids conduct electricity

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

557. Cleavage of a crystal along definite planes shows that

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

558. The three isotopes of hydrogen are

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

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

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

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

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

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

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

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

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

563. The shape of the phosphorus pentachloride molecule is

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

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

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

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

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

566. The specific heat capacity of water is about

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

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

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

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

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

569. 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

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

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

571. Chemical equilibrium is described as dynamic because

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

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

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

573. 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. two neutral solutions D. a strong acid with a weak base E. a weak acid with a weak base

574. 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. 12.5 cm3 B. 50 cm3 C. 2.5 cm3 D. 25 cm3 E. 100 cm3

575. A concentration of one part per million corresponds to

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

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