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Showing 1526 to 1550 of 3046 questions (page 62 of 122).

1526. Hund's rule requires that

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

1527. The bond angle in a molecule with sp3 hybridization and no lone pairs is

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

1528. The dipole moment of carbon dioxide is zero because the molecule is

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

1529. The shape of the ammonia molecule according to VSEPR theory is

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

1530. As bond order increases, the bond length

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

1531. A coordinate covalent bond is present in

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

1532. The ionic character of a bond increases with

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

1533. In benzene, all six carbon to carbon bonds are of equal length because of

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

1534. The hybridization of carbon in ethyne is

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

1535. For an exothermic reaction, the enthalpy change is

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

1536. Hess's law states that the enthalpy change of a reaction

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

1537. The standard enthalpy of formation of an element in its most stable form is

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

1538. 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. all acids have the same concentration C. the salts formed are identical D. the reaction is endothermic E. water is a catalyst

1539. The lattice energy of an ionic compound is determined indirectly using the

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

1540. A system that can exchange energy but not matter with its surroundings is called

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

1541. For the reaction N2 + 3H2 giving 2NH3, increasing the pressure shifts the equilibrium

A. first left then right B. towards the gas with higher molar mass C. not at all D. to the right E. to the left

1542. A catalyst added to a reversible reaction at equilibrium

A. does not change the position of equilibrium B. increases the value of Kc C. shifts the equilibrium to the right D. shifts the equilibrium to the left E. reduces the yield

1543. The pH of a 0.001 mol dm-3 solution of hydrochloric acid is

A. 2 B. 1 C. 3 D. 4 E. 11

1544. At 25 degrees Celsius, the sum of pH and pOH for an aqueous solution is

A. 1 B. 14 D. 10 E. 7

1545. A buffer solution can be prepared from

A. a strong acid and its salt B. a strong base alone C. a neutral salt alone D. a weak acid and its salt with a strong base E. two strong acids

1546. The solubility of a sparingly soluble salt decreases on adding a soluble salt with a common ion. This is called

A. hydrolysis B. the buffer effect C. Le Chatelier suppression of Ksp D. the salt bridge effect E. the common ion effect

1547. Kc has no units when

A. a catalyst is used B. the reaction is exothermic C. the reaction is irreversible D. the total number of moles of gaseous reactants equals that of products E. the reaction is at high pressure

1548. Molality is defined as the number of moles of solute per

A. mole of solvent B. litre of solvent C. kilogram of solvent D. cubic decimetre of solution E. kilogram of solution

1549. Which of the following is not a colligative property?

A. osmotic pressure B. refractive index C. depression of freezing point D. lowering of vapour pressure E. elevation of boiling point

1550. The molal boiling point elevation constant of water is

A. 0.52 K kg mol-1 B. 1.86 K kg mol-1 C. 5.12 K kg mol-1 D. 2.53 K kg mol-1 E. 0.86 K kg mol-1

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