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Showing 626 to 650 of 3046 questions (page 26 of 122).

626. For an ideal gas, the compressibility factor Z is

B. 1 C. less than 1 always D. greater than 1 always E. equal to the pressure

627. Plasma differs from an ordinary gas in that it consists largely of

A. neutral atoms B. ions and free electrons C. molecules only D. liquid droplets E. solid particles

628. Evaporation of a liquid causes cooling because

A. the fastest molecules escape, lowering the average kinetic energy of those left B. the liquid absorbs cold from the air C. the pressure increases D. the volume decreases E. the density increases

629. London dispersion forces become stronger as

A. molar mass and polarizability increase B. molar mass decreases C. the molecule becomes more polar D. temperature increases E. the molecule becomes smaller

630. The property of crystals by which physical properties differ along different directions is called

A. isotropy B. anisotropy C. isomorphism D. polymorphism E. cleavage

631. Two substances with the same crystalline form and analogous chemical formulae are said to be

A. polymorphic B. isomorphic C. allotropic D. amorphous E. isotopic

632. The total number of orbitals in the shell with n = 2 is

A. 2 B. 3 C. 4 D. 8 E. 9

633. For l = 2, the number of permitted values of the magnetic quantum number is

A. 1 B. 3 C. 5 D. 7 E. 2

634. The Pauli exclusion principle states that no two electrons in an atom can have

A. the same energy B. the same spin C. identical values of all four quantum numbers D. the same orbital E. opposite spins

635. The neutron was discovered by

A. J J Thomson B. Rutherford C. Chadwick D. Millikan E. Bohr

636. The lines in the hydrogen emission spectrum arise when electrons

A. are ejected from the atom B. move from lower to higher energy levels C. fall from higher to lower energy levels D. collide with the nucleus E. are shared between atoms

637. The bond angle in water is about 104.5 degrees rather than 109.5 degrees because

A. oxygen is sp2 hybridized B. the two lone pairs repel the bonding pairs more strongly C. hydrogen atoms repel each other D. the molecule is linear E. of hydrogen bonding within the molecule

638. A sigma bond is stronger than a pi bond because

A. it involves sideways overlap B. it involves head on overlap giving greater electron density between the nuclei C. it uses unhybridized orbitals D. it is formed later E. it involves fewer electrons

639. The bond order in a nitrogen molecule is

A. 1 B. 2 C. 3 D. 1.5 E. 2.5

640. Which of the following molecules is polar?

A. carbon dioxide B. boron trifluoride C. methane D. hydrogen chloride E. carbon tetrachloride

641. Metallic bonding is best described as

A. the sharing of electron pairs between two atoms B. the electrostatic attraction between cations and a sea of delocalized electrons C. the transfer of electrons from metal to non-metal D. hydrogen bonding between metal atoms E. dipole induced dipole attraction

642. The standard conditions for reporting thermochemical data are

A. 273 K and 1 atm B. 298 K and 1 atm C. 373 K and 1 atm D. 298 K and 10 atm E. 0 K and 1 atm

643. The enthalpy of combustion of a substance is always

A. positive B. negative C. zero D. equal to the enthalpy of formation E. equal to the lattice energy

644. In calorimetry, the heat exchanged is calculated from

A. q = m c delta T B. q = P delta V C. q = nRT D. q = m/c delta T E. q = c delta T / m

645. A bomb calorimeter measures the heat of combustion at constant

A. pressure B. volume C. temperature D. enthalpy E. entropy

646. Internal energy is a state function, which means it depends on

A. the path taken B. only the initial and final states C. the time taken D. the catalyst used E. the container shape

647. A reversible reaction never goes to completion because

A. the catalyst is exhausted B. the reverse reaction becomes appreciable as products accumulate C. the reactants are impure D. the temperature falls E. the pressure drops

648. Raising the temperature of an exothermic reaction at equilibrium

A. shifts it towards the products B. shifts it towards the reactants C. has no effect D. increases Kc E. stops the reaction

649. The pH of pure water at 25 degrees Celsius is

B. 6 C. 7 D. 8 E. 14

650. A larger value of the acid dissociation constant Ka indicates

A. a weaker acid B. a stronger acid C. a neutral solution D. a buffer solution E. a stronger base

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