Chemistry

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Showing 426 to 450 of 1398 questions (page 18 of 56).

426. Phenol is more acidic than ethanol because

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

427. Tollen's reagent is used to distinguish

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

428. Carboxylic acids are more acidic than alcohols because

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

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

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

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

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

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

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

432. Nylon 6,6 is an example of

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

433. Which of the following is a reducing sugar?

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

434. The percentage of nitrogen in urea is about

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

435. Depletion of stratospheric ozone is mainly caused by

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

436. Acid rain is caused mainly by the oxides of

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

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

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

438. The stationary phase in thin layer chromatography is usually

A. silica gel or alumina B. the sample itself C. air D. water only E. the mobile solvent

439. The molar mass of carbon dioxide is

A. 28 g mol-1 B. 44 g mol-1 C. 12 g mol-1 D. 32 g mol-1 E. 48 g mol-1

440. One atomic mass unit is equal to

A. 1.6 x 10^-19 kg B. 6.02 x 10^-23 kg C. 9.1 x 10^-31 kg D. 1.661 x 10^-27 kg E. 1.661 x 10^-24 kg

441. The total number of atoms in one mole of methane is

A. 6.02 x 10^23 B. 3.01 x 10^24 C. 2.41 x 10^24 D. 5 x 10^23 E. 1.204 x 10^24

442. The molecular formula of a compound is related to its empirical formula by

A. multiplication by a whole number B. division by a whole number C. addition of a constant D. subtraction of hydrogen E. the ratio of densities only

443. Percentage yield is calculated as

A. actual yield minus theoretical yield B. moles of product times 100 C. actual yield divided by theoretical yield times 100 D. theoretical yield divided by actual yield times 100 E. mass of reactants divided by mass of products

444. Distillation under reduced pressure is used for liquids that

A. form no vapour B. decompose at their normal boiling points C. have very low boiling points D. are highly volatile E. are immiscible with water

445. A desiccator is used to

A. heat substances strongly B. weigh precipitates C. dissolve solids D. keep substances free from moisture while cooling E. distil liquids

446. A sharp and constant melting point is used as a criterion of

A. purity B. conductivity C. density D. volatility E. solubility

447. In descending paper chromatography, the solvent moves

A. upwards by capillary action B. horizontally only C. in a circle D. in the vapour phase only E. downwards under gravity

448. At constant volume, the pressure of a fixed mass of gas is directly proportional to its

A. number of collisions only B. density C. absolute temperature D. volume E. molar mass

449. The volume occupied by 2 moles of an ideal gas at STP is

A. 44.8 dm3 B. 24.0 dm3 C. 11.2 dm3 D. 22.4 dm3 E. 5.6 dm3

450. Real gases deviate most from ideal behaviour at

A. high temperature and high pressure B. low temperature and high pressure C. high temperature and low pressure D. low temperature and low pressure E. standard conditions

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