Chemistry

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Showing 1101 to 1125 of 1398 questions (page 45 of 56).

1101. A sharp and constant melting point is used as a criterion of

A. purity B. density C. volatility D. solubility E. conductivity

1102. In descending paper chromatography, the solvent moves

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

1103. At constant volume, the pressure of a fixed mass of gas is directly proportional to its

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

1104. The volume occupied by 2 moles of an ideal gas at STP is

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

1105. Real gases deviate most from ideal behaviour at

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

1106. For an ideal gas, the compressibility factor Z is

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

1107. Plasma differs from an ordinary gas in that it consists largely of

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

1108. Evaporation of a liquid causes cooling because

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

1109. London dispersion forces become stronger as

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

1110. The property of crystals by which physical properties differ along different directions is called

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

1111. Two substances with the same crystalline form and analogous chemical formulae are said to be

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

1112. The total number of orbitals in the shell with n = 2 is

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

1113. For l = 2, the number of permitted values of the magnetic quantum number is

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

1114. The Pauli exclusion principle states that no two electrons in an atom can have

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

1115. The neutron was discovered by

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

1116. The lines in the hydrogen emission spectrum arise when electrons

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

1117. 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. of hydrogen bonding within the molecule E. the molecule is linear

1118. A sigma bond is stronger than a pi bond because

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

1119. The bond order in a nitrogen molecule is

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

1120. Which of the following molecules is polar?

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

1121. 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. hydrogen bonding between metal atoms D. the electrostatic attraction between cations and a sea of delocalized electrons E. dipole induced dipole attraction

1122. The standard conditions for reporting thermochemical data are

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

1123. The enthalpy of combustion of a substance is always

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

1124. In calorimetry, the heat exchanged is calculated from

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

1125. A bomb calorimeter measures the heat of combustion at constant

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

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