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Showing 1276 to 1300 of 3046 questions (page 52 of 122).

1276. The complete combustion of one mole of methane requires oxygen of amount

A. 1 mol B. 2 mol C. 3 mol D. 1.5 mol E. 0.5 mol

1277. For solvent extraction to work, the two solvents used must be

A. of the same density B. both aqueous C. immiscible with each other D. miscible with each other E. chemically identical

1278. A Buchner funnel with a filter flask is used for

A. titration B. distillation C. crystallization D. sublimation E. filtration under suction

1279. The solution left after crystals have separated out during crystallization is called the

A. mother liquor B. supernatant gas C. distillate D. eluent E. filtrate only

1280. In thin layer chromatography, the stationary phase is supported on

A. a strip of paper B. a metal wire C. a glass or plastic plate D. a filter funnel E. a column of solvent

1281. A gas occupies 2 dm3 at 1 atm. At constant temperature and 4 atm its volume becomes

A. 4 dm3 B. 1 dm3 C. 8 dm3 D. 0.5 dm3 E. 2 dm3

1282. A gas occupying 273 cm3 at 273 K is heated at constant pressure to 546 K. Its new volume is

A. 409 cm3 B. 273 cm3 C. 136 cm3 D. 1092 cm3 E. 546 cm3

1283. Standard temperature and pressure are defined as

A. 298 K and 1 atm B. 0 K and zero pressure C. 273 K and 760 mm of mercury only at the equator D. 373 K and 1 atm E. 273.15 K and 1 atm

1284. The volume occupied by 0.5 mol of any ideal gas at STP is

A. 2.24 dm3 B. 11.2 dm3 C. 22.4 dm3 D. 5.6 dm3 E. 44.8 dm3

1285. A hydrogen bond is typically

A. weaker than a covalent bond but stronger than a London force B. identical to an ionic bond C. of zero energy D. stronger than a covalent bond E. weaker than a London dispersion force

1286. Ice floats on water because

A. it contains dissolved air only B. it is warmer C. hydrogen bonding gives ice an open structure of lower density D. water is denser at 0 degrees Celsius than at 4 degrees Celsius E. ice is amorphous

1287. Molecular solids are generally

A. ionic in character B. network covalent C. soft with low melting points D. hard with high melting points E. good conductors of electricity

1288. Ionic solids conduct electricity

A. only when molten or dissolved B. in the solid state C. only as vapours D. never E. only at absolute zero

1289. Cleavage of a crystal along definite planes shows that

A. the crystal is anisotropic in colour only B. the crystal contains water C. the crystal is amorphous D. the particles are arranged in an ordered pattern E. the crystal is ionic

1290. The three isotopes of hydrogen are

A. hydrogen, helium and lithium B. protium, deuterium and tritium C. ortho, meta and para hydrogen D. alpha, beta and gamma hydrogen E. hydride, proton and hydronium

1291. The maximum number of electrons that a d subshell can hold is

A. 10 B. 2 C. 18 D. 14 E. 6

1292. The wave mechanical model of the atom is based on the equation formulated by

A. Planck B. Bohr C. Schrodinger D. Rutherford E. Chadwick

1293. The existence of discrete spectral lines rather than a continuous spectrum shows that atomic energy is

A. infinite B. quantized C. independent of the electron D. zero E. continuous

1294. The number of lone pairs on the oxygen atom in a water molecule is

A. 4 B. 1 C. 3 E. 2

1295. The shape of the phosphorus pentachloride molecule is

A. tetrahedral B. see saw C. trigonal bipyramidal D. octahedral E. square planar

1296. The number of sigma bonds in an ethyne molecule is

A. 2 B. 3 C. 4 D. 1 E. 5

1297. The number of pi bonds in a benzene molecule, on the Kekule representation, is

A. 3 C. 6 D. 2 E. 1

1298. The specific heat capacity of water is about

A. 2.09 J g-1 K-1 B. 4.18 J g-1 K-1 C. 8.314 J g-1 K-1 D. 1.0 J g-1 K-1 E. 336 J g-1 K-1

1299. The dissolution of ammonium chloride in water lowers the temperature, so the process is

A. endothermic B. adiabatic C. exothermic D. spontaneous only above 100 degrees Celsius E. isothermal

1300. The imaginary surface separating a system from its surroundings is called the

A. interface B. phase C. meniscus D. medium E. boundary

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