Chemistry

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Showing 776 to 800 of 1398 questions (page 32 of 56).

776. 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

777. 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

778. 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

779. 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

780. The oxidation number of sulphur in sulphuric acid is

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

781. 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

782. 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

783. 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

784. 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

785. 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

786. 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

787. 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

788. 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

789. 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

790. 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

791. The element with the highest electronegativity is

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

792. 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

793. 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

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

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

795. Alkali metals are stored under kerosene oil because they

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

796. Among the alkali metals, lithium has the highest

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

797. The chemical formula of gypsum is

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

798. Sodium carbonate is used industrially mainly in the manufacture of

A. fertilizer B. plastics C. cement D. glass E. petrol

799. Carbon monoxide is highly toxic because it

A. is acidic B. dissolves in water C. decomposes in the lungs D. reacts with nitrogen E. binds strongly to haemoglobin in place of oxygen

800. The catalyst used in the contact process for manufacturing sulphuric acid is

A. nickel B. aluminium chloride C. platinum D. iron E. vanadium pentoxide

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