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226. Which oxide of nitrogen is known as laughing gas?

A. NO B. N2O C. NO2 D. N2O5 E. N2O3

227. A transition element is one that has a partially filled

A. s subshell B. p subshell C. d subshell D. f subshell E. valence shell of eight electrons

228. The colour of most transition metal ions in solution is due to

A. s to p transitions B. d to d electronic transitions C. nuclear transitions D. hydrogen bonding E. ionic size

229. In the complex ion hexaamminecobalt(III), the coordination number of cobalt is

A. 3 B. 4 C. 5 D. 6 E. 2

230. EDTA is an example of a

A. monodentate ligand B. bidentate ligand C. hexadentate chelating ligand D. neutral molecule that cannot coordinate E. cation

231. Transition metals show variable oxidation states because

A. their atomic radii are large B. the energies of the ns and (n-1)d electrons are close C. they are all diamagnetic D. they form only ionic compounds E. their ionization energies are very high

232. The hybridization of each carbon atom in ethene is

A. sp B. sp2 C. sp3 D. sp3d E. sp3d2

233. The halogenation of alkanes in sunlight proceeds by a

A. nucleophilic substitution mechanism B. electrophilic addition mechanism C. free radical substitution mechanism D. elimination mechanism E. rearrangement

234. According to Markownikoff's rule, addition of hydrogen bromide to propene gives mainly

A. 1-bromopropane B. 2-bromopropane C. 1,2-dibromopropane D. propan-1-ol E. propane

235. Benzene characteristically undergoes

A. electrophilic addition B. electrophilic substitution C. nucleophilic addition D. free radical addition E. elimination

236. A primary alkyl halide reacting with a strong nucleophile typically follows

A. the SN1 mechanism B. the SN2 mechanism C. free radical substitution D. E1 elimination E. electrophilic addition

237. A Grignard reagent has the general formula

A. RMgX B. RLiX C. RNaX D. RZnX E. RAlX

238. Controlled oxidation of a primary alcohol gives

A. a ketone B. an aldehyde C. an ester D. an alkane E. an ether

239. Phenol is more acidic than ethanol because

A. it has a higher molar mass B. the phenoxide ion is stabilized by resonance C. it contains a benzene ring that repels electrons D. it is a stronger nucleophile E. it is insoluble in water

240. Tollen's reagent is used to distinguish

A. alcohols from ethers B. aldehydes from ketones C. acids from esters D. alkanes from alkenes E. amines from amides

241. Carboxylic acids are more acidic than alcohols because

A. they have a longer chain B. the carboxylate ion is resonance stabilized C. they are less soluble D. they contain two oxygen atoms of equal bond length only in the acid E. they are liquids

242. The reaction of a carboxylic acid with an alcohol in the presence of an acid catalyst is called

A. saponification B. esterification C. hydrolysis D. decarboxylation E. nitration

243. At its isoelectric point, an amino acid exists mainly as

A. a cation B. an anion C. a zwitterion D. a neutral unionized molecule E. a free radical

244. The linkage joining amino acid residues in a protein is

A. a glycosidic bond B. a peptide bond C. an ester linkage D. a disulphide bond only E. an ionic bond

245. Nylon 6,6 is an example of

A. an addition polymer B. a condensation polymer C. a natural polymer D. an elastomer formed by vulcanization E. a silicone

246. Which of the following is a reducing sugar?

A. sucrose B. glucose C. starch D. cellulose E. glycogen

247. The percentage of nitrogen in urea is about

A. 21% B. 35% C. 46% D. 60% E. 82%

248. Depletion of stratospheric ozone is mainly caused by

A. carbon dioxide B. chlorofluorocarbons C. sulphur dioxide D. methane E. nitrogen gas

249. Acid rain is caused mainly by the oxides of

A. carbon and hydrogen B. sulphur and nitrogen C. sodium and potassium D. iron and copper E. silicon and boron

250. The chief greenhouse gas responsible for the enhanced greenhouse effect is

A. oxygen B. nitrogen C. carbon dioxide D. argon E. helium

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