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Showing 1301 to 1325 of 3046 questions (page 53 of 122).

1301. Enthalpy changes of reaction are normally quoted in

A. kJ K-1 B. J K-1 mol-1 C. kJ mol-1 D. J E. mol kJ-1

1302. The enthalpy of formation of a compound can be found from enthalpies of combustion using

A. Le Chatelier's principle B. Dalton's law C. Raoult's law D. Hess's law E. Graham's law

1303. Chemical equilibrium is described as dynamic because

A. the reaction has stopped B. the catalyst is consumed C. the temperature keeps changing D. both forward and reverse reactions continue at equal rates E. the concentrations keep changing

1304. The pH of a 0.01 mol dm-3 solution of sodium hydroxide at 25 degrees Celsius is

A. 12 B. 14 C. 2 D. 10 E. 7

1305. Phenolphthalein is a suitable indicator for the titration of

A. a strong acid with a strong acid B. a weak acid with a strong base C. two neutral solutions D. a strong acid with a weak base E. a weak acid with a weak base

1306. The volume of 0.1 mol dm-3 hydrochloric acid needed to neutralize 25 cm3 of 0.1 mol dm-3 sodium hydroxide is

A. 12.5 cm3 B. 50 cm3 C. 2.5 cm3 D. 25 cm3 E. 100 cm3

1307. A concentration of one part per million corresponds to

A. 1 g of solute in 1 g of solution B. 1 mg of solute in 1 kg of solution C. 1 cm3 of solute in 1 dm3 D. 1 g of solute in 1 kg of solution E. 1 mol of solute in 10^6 dm3

1308. Dissolving 0.5 mol of a solute in 500 g of solvent gives a molality of

A. 0.5 m B. 5 m C. 0.25 m D. 2 m E. 1 m

1309. The mass of sodium hydroxide required to prepare 1 dm3 of a 0.5 mol dm-3 solution is

A. 5 g B. 80 g C. 20 g D. 10 g E. 40 g

1310. Colligative properties are used experimentally to determine the

A. colour of a solute B. density of the solvent C. molar mass of a solute D. boiling point of the solvent only E. viscosity of the solution

1311. A cell placed in a hypertonic solution will

A. shrink as water leaves it B. divide C. gain solute rapidly D. swell and burst E. remain unchanged

1312. Rusting of iron requires the presence of

A. nitrogen B. both oxygen and water C. oxygen only D. carbon dioxide only E. water only

1313. Galvanizing protects iron because zinc

A. prevents the entry of nitrogen only B. is a better conductor C. is less reactive than iron D. forms an ionic bond with iron E. is more reactive and corrodes preferentially as a sacrificial metal

1314. During electroplating, the article to be plated is made the

A. cathode B. reference electrode C. anode D. salt bridge E. electrolyte

1315. According to Faraday's first law, the mass of a substance deposited during electrolysis is proportional to

A. the electrode area B. the voltage applied C. the temperature D. the quantity of charge passed E. the resistance of the cell

1316. The standard reduction potential of the zinc electrode is about

A. +0.34 V B. -0.34 V C. 0.00 V D. +0.76 V E. -0.76 V

1317. The usual unit of reaction rate is

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

1318. According to collision theory, a collision leads to reaction only if the molecules have sufficient energy and

A. a catalyst present B. equal masses C. the same charge D. identical speeds E. the correct orientation

1319. A reaction initiated by the absorption of light is called

A. a chain terminating reaction B. an electrochemical reaction C. a photochemical reaction D. a thermal reaction E. an autocatalytic reaction

1320. For a main group element, the number of valence electrons is indicated by its

A. atomic mass B. period number C. group number D. oxidation state only E. atomic radius

1321. The second ionization energy of an element is always greater than the first because

A. the atom becomes larger B. the nuclear charge decreases C. the electron is closer to the nucleus in the neutral atom D. shielding increases E. an electron is removed from a positively charged ion

1322. Across a period, the character of the oxides changes from

A. unchanged B. basic to neutral only C. acidic to neutral only D. basic through amphoteric to acidic E. acidic through amphoteric to basic

1323. The transition elements occupy the

A. s block B. d block C. f block D. p block E. noble gas group

1324. The chemical inertness of the noble gases is due to their

A. completely filled valence shells B. large size C. radioactivity D. low atomic mass E. high density

1325. The hydrides of the alkali metals are

A. covalent and volatile B. ionic solids containing the hydride ion C. non-existent D. metallic E. polymeric

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