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Showing 2851 to 2875 of 3046 questions (page 115 of 122).

2851. If 5 g of a product is obtained where 8 g was theoretically possible, the percentage yield is

A. 160% B. 37.5% C. 80% D. 50% E. 62.5%

2852. A gram atom of an element is

A. the mass of one molecule B. one atom of the element C. its atomic number in grams D. always 12 g E. the mass in grams numerically equal to its relative atomic mass

2853. A mass spectrometer separates and detects ions after they have been

A. dissolved in water B. ionized, accelerated and deflected C. burnt in oxygen D. cooled and condensed E. precipitated

2854. In the reaction of nitrogen with hydrogen to form ammonia, 1 mol of nitrogen reacting completely gives ammonia of amount

A. 1 mol B. 1.5 mol C. 0.5 mol D. 2 mol E. 3 mol

2855. Fractional crystallization is used to separate

A. two solids of different solubilities from the same solution B. two immiscible liquids C. isotopes D. a solid from a gas E. two gases

2856. Decantation is suitable when the precipitate is

A. gaseous B. very fine and colloidal C. heavy and settles quickly D. volatile E. soluble in the solvent

2857. In column chromatography, the component that is most strongly adsorbed on the stationary phase

A. travels slowest and is eluted last B. travels fastest C. changes colour D. dissolves the column E. does not move at all

2858. In a mixture of 2 mol of nitrogen and 3 mol of oxygen, the mole fraction of oxygen is

A. 0.2 B. 0.5 C. 0.4 D. 1.5 E. 0.6

2859. If the mole fraction of oxygen in a gas mixture at 2 atm total pressure is 0.25, its partial pressure is

A. 0.25 atm B. 0.5 atm C. 1 atm D. 8 atm E. 2 atm

2860. Which gas would be expected to show the greatest deviation from ideal behaviour?

A. nitrogen B. ammonia C. helium D. neon E. hydrogen

2861. The difference between evaporation and boiling is that boiling

A. occurs throughout the liquid at a fixed temperature B. lowers the temperature C. occurs only at the surface D. requires no heat E. occurs at all temperatures

2862. The number of atoms per unit cell in a simple cubic lattice is

A. 8 B. 2 C. 4 D. 1 E. 6

2863. Lattice energy of an ionic compound increases with

A. increasing ionic radii B. increasing coordination number only C. increasing ionic charges and decreasing ionic radii D. increasing temperature E. decreasing charges

2864. Hydrogen fluoride exists in the liquid state as zig zag chains because of

A. London forces only B. hydrogen bonding between molecules C. covalent network bonding D. ionic bonding E. metallic bonding

2865. Orbitals of the same subshell that have equal energy in an isolated atom are described as

A. degenerate B. polar C. hybrid D. saturated E. antibonding

2866. The dual nature of matter was proposed by

A. de Broglie B. Rutherford C. Chadwick D. Bohr E. Dalton

2867. The bond angle in boron trifluoride is

A. 180 degrees B. 104.5 degrees C. 120 degrees D. 109.5 degrees E. 90 degrees

2868. The sulphur dioxide molecule is

A. linear B. square planar C. tetrahedral D. trigonal planar E. bent

2869. A molecule may contain polar bonds and still have no net dipole moment if it is

A. linear only B. symmetrical so that the bond dipoles cancel C. hydrogen bonded D. paramagnetic E. ionic

2870. The number of sigma bonds in a methane molecule is

A. 1 B. 2 C. 5 D. 3 E. 4

2871. On an enthalpy level diagram for an exothermic reaction, the products lie

A. above the reactants B. at zero enthalpy C. below the reactants D. above the activated complex E. at the same level as the reactants

2872. Raising the temperature of 100 g of water by 10 K requires about

A. 41800 J B. 10 J C. 4180 J D. 41.8 J E. 418 J

2873. An aqueous solution of ammonium chloride is

A. a buffer of pH 7 B. acidic C. amphoteric D. neutral E. basic

2874. For the reaction in which one mole of gas gives two moles of gas, an increase in volume at constant temperature

A. shifts the equilibrium to the right B. has no effect C. shifts the equilibrium to the left D. stops the reaction E. decreases Kc

2875. In an acid base titration, the point at which the amounts of acid and base are chemically equivalent is the

A. buffer region B. end point of the indicator only C. isoelectric point D. equivalence point E. neutral point of water

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