Chemistry

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Showing 376 to 400 of 1398 questions (page 16 of 56).

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

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

377. A buffer solution can be prepared from

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

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

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

379. Kc has no units when

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

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

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

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

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

382. The molal boiling point elevation constant of water is

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

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

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

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

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

385. 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

386. The oxidation number of manganese in potassium permanganate is

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

387. 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

388. 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. 965 C E. 9650 C

389. In a galvanic cell, oxidation occurs at the

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

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

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

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

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

392. In an electrolytic cell, electrical energy is

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

393. The half life of a first order reaction

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

394. A catalyst increases the rate of reaction by

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

395. The order of a reaction is determined by

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

396. For a zero order reaction, the rate is

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

397. The Arrhenius equation relates the rate constant to

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

398. Enzyme catalysed reactions are highly

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

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

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

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

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

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