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Showing 476 to 500 of 1398 questions (page 20 of 56).

476. An aqueous solution of sodium acetate is

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

477. The solubility product expression for silver chloride is

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

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

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

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

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

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

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

481. The solubility of most gases in water

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

482. An oxidizing agent is a species that

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

483. The oxidation number of sulphur in sulphuric acid is

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

484. The standard cell potential is calculated as

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

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

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

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

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

487. A nickel cadmium cell is an example of

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

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

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

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

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

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

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

491. A rise in temperature of about 10 K commonly

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

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

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

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

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

494. The element with the highest electronegativity is

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

495. Metallic character generally

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

496. The screening or shielding effect of inner electrons

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

497. The number of elements in the fourth period of the periodic table is

A. 32 B. 2 C. 10 D. 8 E. 18

498. Alkali metals are stored under kerosene oil because they

A. are volatile B. are radioactive C. react vigorously with air and moisture D. dissolve in water slowly E. sublime readily

499. Among the alkali metals, lithium has the highest

A. density B. atomic number C. ionization energy D. reactivity with water E. atomic radius

500. The chemical formula of gypsum is

A. CaSO4.2H2O B. CaSO4.(1/2)H2O C. CaO D. CaSO4 E. CaCO3

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