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Showing 876 to 900 of 3046 questions (page 36 of 122).

876. The boiling point of a liquid at reduced external pressure

A. decreases B. becomes zero C. doubles D. remains unchanged E. increases

877. The coordination number of each ion in a sodium chloride crystal is

A. 2 B. 8 C. 12 D. 4 E. 6

878. The existence of a substance in more than one crystalline form is called

A. allotropy in solutions only B. isotopy C. polymorphism D. anisotropy E. isomorphism

879. Which type of solid has the highest melting point?

A. amorphous B. molecular C. covalent network D. metallic E. ionic

880. The maximum number of electrons that can occupy the shell with n = 3 is

A. 6 B. 8 C. 32 D. 10 E. 18

881. For an electron in a 3d orbital, the azimuthal quantum number l is

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

882. The ground state electronic configuration of chromium (Z = 24) is

A. [Ar] 3d6 B. [Ar] 3d5 4s1 C. [Ar] 3d3 4s3 D. [Ar] 4s2 4p4 E. [Ar] 3d4 4s2

883. Rutherford's gold foil experiment established the existence of

A. a small dense positively charged nucleus B. the neutron C. energy levels D. the electron E. orbitals

884. The energy of a photon of frequency nu is given by

A. h nu2 B. h nu C. h/nu2 D. h/nu E. nu/h

885. The shape of a p orbital is

A. spherical B. planar triangular C. double dumb bell D. tetrahedral E. dumb bell

886. Hund's rule requires that

A. no two electrons can have the same spin B. electrons pair up before occupying empty degenerate orbitals C. degenerate orbitals are singly occupied with parallel spins before pairing D. the lowest energy orbital is filled last E. d orbitals fill before s orbitals of the same shell

887. The bond angle in a molecule with sp3 hybridization and no lone pairs is

A. 90 degrees B. 120 degrees C. 109.5 degrees D. 107 degrees E. 104.5 degrees

888. The dipole moment of carbon dioxide is zero because the molecule is

A. tetrahedral B. linear and symmetrical C. non-polar in its bonds D. ionic E. angular

889. The shape of the ammonia molecule according to VSEPR theory is

A. trigonal pyramidal B. bent with 104.5 degrees C. linear D. trigonal planar E. tetrahedral

890. As bond order increases, the bond length

A. first increases then decreases B. remains constant C. becomes zero D. decreases E. increases

891. A coordinate covalent bond is present in

A. methane B. ethene C. chlorine D. sodium chloride E. the ammonium ion

892. The ionic character of a bond increases with

A. increasing bond order B. increasing covalent radius C. increasing electronegativity difference D. decreasing atomic size only E. decreasing electronegativity difference

893. In benzene, all six carbon to carbon bonds are of equal length because of

A. sp3 hybridization B. hydrogen bonding C. ionic character D. free rotation E. resonance delocalization

894. The hybridization of carbon in ethyne is

A. sp3 B. sp C. sp3d D. sp2 E. unhybridized

895. For an exothermic reaction, the enthalpy change is

A. negative B. undefined C. zero D. positive E. always equal to the activation energy

896. Hess's law states that the enthalpy change of a reaction

A. equals the activation energy B. depends on the path taken C. depends only on temperature D. is independent of the path taken E. is always negative

897. The standard enthalpy of formation of an element in its most stable form is

A. always positive B. equal to its bond energy C. always negative D. equal to its atomization energy E. zero

898. The enthalpy of neutralization of a strong acid by a strong base is nearly constant because

A. the reaction is always the combination of H+ and OH- to give water B. the salts formed are identical C. all acids have the same concentration D. the reaction is endothermic E. water is a catalyst

899. The lattice energy of an ionic compound is determined indirectly using the

A. Kelvin scale B. Haber process C. Born Haber cycle D. Carnot cycle E. Hess cycle for combustion only

900. A system that can exchange energy but not matter with its surroundings is called

A. an adiabatic system only B. a closed system C. a homogeneous system D. an open system E. an isolated system

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