Chemistry

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Showing 676 to 700 of 1398 questions (page 28 of 56).

676. 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

677. 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

678. 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

679. 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

680. Raoult's law states that the partial vapour pressure of a component in a solution is proportional to its

A. mass B. molarity C. volume fraction D. molality E. mole fraction

681. A mixture that distils at constant composition and cannot be separated further by fractional distillation is called

A. an azeotrope B. an emulsion C. a saturated solution D. an ideal solution E. a colloid

682. An ideal solution is one in which

A. hydrogen bonding is formed on mixing B. the volume decreases on mixing C. the vapour pressure is zero D. the components react E. the enthalpy of mixing is zero and Raoult's law is obeyed

683. The oxidation number of manganese in potassium permanganate is

A. +3 B. +4 C. +2 D. +7 E. +6

684. The standard electrode potential of the standard hydrogen electrode is taken as

A. +1.00 V B. 0.00 V C. -0.76 V D. -1.00 V E. +0.76 V

685. One faraday of charge is equal to about

A. 1.6 x 10^-19 C B. 6.02 x 10^23 C C. 96500 C D. 9650 C E. 965 C

686. In a galvanic cell, oxidation occurs at the

A. anode B. porous partition C. cathode D. salt bridge E. electrolyte

687. During the discharge of a lead accumulator, the substance formed at both electrodes is

A. hydrogen B. lead dioxide C. sulphuric acid D. lead E. lead sulphate

688. A metal placed higher in the electrochemical series than another will

A. be reduced by it B. displace it from its salt solution C. not react with it D. form a stronger acid E. have a higher electrode potential

689. In an electrolytic cell, electrical energy is

A. stored as heat only B. produced from a spontaneous reaction C. used to drive a non-spontaneous reaction D. converted into light only E. not involved

690. The half life of a first order reaction

A. increases as the reaction proceeds B. is proportional to the rate constant C. doubles when concentration doubles D. is independent of the initial concentration E. depends on the initial concentration

691. A catalyst increases the rate of reaction by

A. shifting the equilibrium B. increasing the concentration of reactants C. lowering the activation energy D. increasing the temperature E. increasing the enthalpy change

692. The order of a reaction is determined by

A. the enthalpy change B. the molecularity C. the equilibrium constant D. experiment E. the stoichiometric equation

693. For a zero order reaction, the rate is

A. inversely proportional to concentration B. independent of the concentration of the reactant C. zero at all times D. proportional to the concentration of the reactant E. proportional to the square of the concentration

694. The Arrhenius equation relates the rate constant to

A. enthalpy and entropy B. concentration and volume C. pH and temperature D. pressure and volume E. temperature and activation energy

695. Enzyme catalysed reactions are highly

A. specific B. independent of pH C. irreversible at all temperatures D. endothermic E. non-specific

696. The modern periodic law states that the properties of elements are a periodic function of their

A. valency B. atomic volume C. atomic number D. atomic mass E. density

697. Across a period from left to right, atomic radius generally

A. increases then decreases B. decreases C. remains constant D. increases E. doubles

698. Ionization energy generally decreases

A. with increasing nuclear charge B. with decreasing atomic size C. for half filled subshells D. down a group E. across a period

699. Lithium shows a diagonal relationship with

A. beryllium B. aluminium C. sodium D. calcium E. magnesium

700. Hydration energy of an ion increases with

A. increasing charge density B. increasing ionic size C. decreasing charge D. decreasing charge density E. increasing atomic mass

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