Chemistry

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Showing 1276 to 1300 of 1398 questions (page 52 of 56).

1276. Eutrophication of a lake is caused mainly by

A. low temperature B. high dissolved oxygen C. excess chlorine D. excess nutrients such as nitrates and phosphates E. acid rain alone

1277. Dissolved oxygen in a river falls when organic pollution rises because

A. the pollutant displaces the oxygen physically B. oxygen reacts with the pollutant directly only C. the water becomes acidic D. the temperature falls E. micro-organisms consume oxygen while decomposing the organic matter

1278. Infrared spectroscopy is used chiefly to identify

A. isotopes B. functional groups C. optical activity D. molar mass E. crystal structure

1279. If 5 g of a product is obtained where 8 g was theoretically possible, the percentage yield is

A. 160% B. 37.5% C. 80% D. 50% E. 62.5%

1280. A gram atom of an element is

A. the mass of one molecule B. one atom of the element C. its atomic number in grams D. always 12 g E. the mass in grams numerically equal to its relative atomic mass

1281. A mass spectrometer separates and detects ions after they have been

A. dissolved in water B. ionized, accelerated and deflected C. burnt in oxygen D. cooled and condensed E. precipitated

1282. In the reaction of nitrogen with hydrogen to form ammonia, 1 mol of nitrogen reacting completely gives ammonia of amount

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

1283. Fractional crystallization is used to separate

A. two solids of different solubilities from the same solution B. two immiscible liquids C. isotopes D. a solid from a gas E. two gases

1284. Decantation is suitable when the precipitate is

A. gaseous B. very fine and colloidal C. heavy and settles quickly D. volatile E. soluble in the solvent

1285. In column chromatography, the component that is most strongly adsorbed on the stationary phase

A. travels slowest and is eluted last B. travels fastest C. changes colour D. dissolves the column E. does not move at all

1286. In a mixture of 2 mol of nitrogen and 3 mol of oxygen, the mole fraction of oxygen is

A. 0.2 B. 0.5 C. 0.4 D. 1.5 E. 0.6

1287. If the mole fraction of oxygen in a gas mixture at 2 atm total pressure is 0.25, its partial pressure is

A. 0.25 atm B. 0.5 atm C. 1 atm D. 8 atm E. 2 atm

1288. Which gas would be expected to show the greatest deviation from ideal behaviour?

A. nitrogen B. ammonia C. helium D. neon E. hydrogen

1289. The difference between evaporation and boiling is that boiling

A. occurs throughout the liquid at a fixed temperature B. lowers the temperature C. occurs only at the surface D. requires no heat E. occurs at all temperatures

1290. The number of atoms per unit cell in a simple cubic lattice is

A. 8 B. 2 C. 4 D. 1 E. 6

1291. Lattice energy of an ionic compound increases with

A. increasing ionic radii B. increasing coordination number only C. increasing ionic charges and decreasing ionic radii D. increasing temperature E. decreasing charges

1292. Hydrogen fluoride exists in the liquid state as zig zag chains because of

A. London forces only B. hydrogen bonding between molecules C. covalent network bonding D. ionic bonding E. metallic bonding

1293. Orbitals of the same subshell that have equal energy in an isolated atom are described as

A. degenerate B. polar C. hybrid D. saturated E. antibonding

1294. The dual nature of matter was proposed by

A. de Broglie B. Rutherford C. Chadwick D. Bohr E. Dalton

1295. The bond angle in boron trifluoride is

A. 180 degrees B. 104.5 degrees C. 120 degrees D. 109.5 degrees E. 90 degrees

1296. The sulphur dioxide molecule is

A. linear B. square planar C. tetrahedral D. trigonal planar E. bent

1297. A molecule may contain polar bonds and still have no net dipole moment if it is

A. linear only B. symmetrical so that the bond dipoles cancel C. hydrogen bonded D. paramagnetic E. ionic

1298. The number of sigma bonds in a methane molecule is

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

1299. On an enthalpy level diagram for an exothermic reaction, the products lie

A. above the reactants B. at zero enthalpy C. below the reactants D. above the activated complex E. at the same level as the reactants

1300. Raising the temperature of 100 g of water by 10 K requires about

A. 41800 J B. 10 J C. 4180 J D. 41.8 J E. 418 J

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