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Showing 1751 to 1775 of 3046 questions (page 71 of 122).

1751. A reversible reaction never goes to completion because

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

1752. Raising the temperature of an exothermic reaction at equilibrium

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

1753. The pH of pure water at 25 degrees Celsius is

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

1754. A larger value of the acid dissociation constant Ka indicates

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

1755. An aqueous solution of sodium acetate is

A. acidic B. basic C. amphoteric D. a buffer on its own only at pH 7 E. neutral

1756. The solubility product expression for silver chloride is

A. [Ag+][Cl-] B. [Ag+]2[Cl-] C. [Ag+]/[Cl-] D. [Ag+][Cl-]2 E. [AgCl]/[Ag+][Cl-]

1757. Dissolving 0.5 mol of solute in enough water to make 250 cm3 of solution gives a molarity of

A. 0.5 M B. 0.125 M C. 1 M D. 2 M E. 5 M

1758. The osmotic pressure of a dilute solution is given by

A. pi = RT/nV B. pi V = nRT C. pi V = n/RT D. pi = n/V E. pi = nRTV

1759. Molarity changes with temperature but molality does not, because molarity depends on

A. the volume of solution B. the mass of solvent C. the nature of the solute D. the mass of solute E. the number of moles of solute

1760. The solubility of most gases in water

A. increases with temperature B. is independent of temperature C. decreases with temperature D. increases with decreasing pressure E. is unaffected by pressure

1761. An oxidizing agent is a species that

A. increases its own oxidation number B. gains electrons C. donates protons D. loses electrons E. always contains oxygen

1762. The oxidation number of sulphur in sulphuric acid is

B. +4 C. -2 D. +2 E. +6

1763. The standard cell potential is calculated as

A. the average of the two potentials B. the sum of the two reduction potentials C. always zero D. cathode potential minus anode potential E. anode potential minus cathode potential

1764. The products of the electrolysis of concentrated aqueous sodium chloride using inert electrodes are

A. sodium and oxygen B. oxygen and hydrogen only C. hydrogen, chlorine and sodium hydroxide D. sodium and chlorine E. chlorine and oxygen only

1765. The function of the salt bridge in a galvanic cell is to

A. supply electrons to the circuit B. maintain electrical neutrality in the two half cells C. act as the cathode D. increase the cell voltage E. prevent oxidation

1766. A nickel cadmium cell is an example of

A. a concentration cell B. a fuel cell C. an electrolytic cell only D. a secondary cell E. a primary cell

1767. A hydrogen oxygen fuel cell differs from an ordinary cell in that it

A. is supplied with reactants continuously from outside B. cannot be recharged and so is useless C. stores its reactants internally D. operates without electrodes E. produces no water

1768. The unit of the rate constant for a first order reaction is

A. dm6 mol-2 s-1 B. mol dm-3 s-1 C. dimensionless D. dm3 mol-1 s-1 E. s-1

1769. In a multistep reaction, the overall rate is governed by the

A. fastest step B. step with the most reactants C. slowest step D. first step always E. last step always

1770. A rise in temperature of about 10 K commonly

A. changes the order of the reaction B. roughly doubles the reaction rate C. lowers the activation energy D. halves the reaction rate E. has no effect on the rate

1771. The decomposition of hydrogen peroxide by manganese dioxide is an example of

A. heterogeneous catalysis B. negative catalysis C. autocatalysis D. homogeneous catalysis E. enzyme catalysis

1772. A substance that decreases the rate of a reaction is called

A. a catalyst poison for enzymes only B. a co-factor C. a promoter D. an activator E. an inhibitor

1773. The element with the highest electronegativity is

A. oxygen B. nitrogen C. chlorine D. fluorine E. caesium

1774. Metallic character generally

A. increases across a period B. increases down a group C. is highest for noble gases D. decreases down a group E. is unrelated to position

1775. The screening or shielding effect of inner electrons

A. decreases the effective nuclear charge felt by outer electrons B. has no effect on atomic size C. increases the effective nuclear charge D. only applies to d electrons E. increases ionization energy

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