Chemistry

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Showing 1226 to 1250 of 1398 questions (page 50 of 56).

1226. Chemical equilibrium is described as dynamic because

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

1227. The pH of a 0.01 mol dm-3 solution of sodium hydroxide at 25 degrees Celsius is

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

1228. Phenolphthalein is a suitable indicator for the titration of

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

1229. 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. 2.5 cm3 B. 50 cm3 C. 12.5 cm3 D. 25 cm3 E. 100 cm3

1230. A concentration of one part per million corresponds to

A. 1 mol of solute in 10^6 dm3 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 g of solution E. 1 g of solute in 1 kg of solution

1231. Dissolving 0.5 mol of a solute in 500 g of solvent gives a molality of

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

1232. The mass of sodium hydroxide required to prepare 1 dm3 of a 0.5 mol dm-3 solution is

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

1233. Colligative properties are used experimentally to determine the

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

1234. A cell placed in a hypertonic solution will

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

1235. Rusting of iron requires the presence of

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

1236. Galvanizing protects iron because zinc

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

1237. During electroplating, the article to be plated is made the

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

1238. According to Faraday's first law, the mass of a substance deposited during electrolysis is proportional to

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

1239. The standard reduction potential of the zinc electrode is about

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

1240. The usual unit of reaction rate is

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

1241. According to collision theory, a collision leads to reaction only if the molecules have sufficient energy and

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

1242. A reaction initiated by the absorption of light is called

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

1243. For a main group element, the number of valence electrons is indicated by its

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

1244. The second ionization energy of an element is always greater than the first because

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

1245. Across a period, the character of the oxides changes from

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

1246. The transition elements occupy the

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

1247. The chemical inertness of the noble gases is due to their

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

1248. The hydrides of the alkali metals are

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

1249. Permanent hardness of water is caused mainly by dissolved

A. calcium and magnesium sulphates and chlorides B. potassium nitrate C. dissolved carbon dioxide D. sodium chloride E. calcium and magnesium bicarbonates

1250. Caustic soda is the common name for

A. sodium bicarbonate B. sodium carbonate C. calcium hydroxide D. sodium hydroxide E. sodium chloride

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