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Showing 1726 to 1750 of 3046 questions (page 70 of 122).

1726. In descending paper chromatography, the solvent moves

A. horizontally only B. in a circle C. in the vapour phase only D. upwards by capillary action E. downwards under gravity

1727. At constant volume, the pressure of a fixed mass of gas is directly proportional to its

A. number of collisions only B. volume C. absolute temperature D. density E. molar mass

1728. The volume occupied by 2 moles of an ideal gas at STP is

A. 44.8 dm3 B. 11.2 dm3 C. 22.4 dm3 D. 5.6 dm3 E. 24.0 dm3

1729. Real gases deviate most from ideal behaviour at

A. high temperature and low pressure B. low temperature and high pressure C. standard conditions D. high temperature and high pressure E. low temperature and low pressure

1730. For an ideal gas, the compressibility factor Z is

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

1731. Plasma differs from an ordinary gas in that it consists largely of

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

1732. Evaporation of a liquid causes cooling because

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

1733. London dispersion forces become stronger as

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

1734. The property of crystals by which physical properties differ along different directions is called

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

1735. Two substances with the same crystalline form and analogous chemical formulae are said to be

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

1736. The total number of orbitals in the shell with n = 2 is

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

1737. For l = 2, the number of permitted values of the magnetic quantum number is

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

1738. The Pauli exclusion principle states that no two electrons in an atom can have

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

1739. The neutron was discovered by

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

1740. The lines in the hydrogen emission spectrum arise when electrons

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

1741. The bond angle in water is about 104.5 degrees rather than 109.5 degrees because

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

1742. A sigma bond is stronger than a pi bond because

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

1743. The bond order in a nitrogen molecule is

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

1744. Which of the following molecules is polar?

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

1745. Metallic bonding is best described as

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

1746. The standard conditions for reporting thermochemical data are

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

1747. The enthalpy of combustion of a substance is always

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

1748. In calorimetry, the heat exchanged is calculated from

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

1749. A bomb calorimeter measures the heat of combustion at constant

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

1750. Internal energy is a state function, which means it depends on

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

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