Chemistry

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Showing 251 to 275 of 1398 questions (page 11 of 56).

251. Which of the following molecules is polar?

A. carbon dioxide B. boron trifluoride C. methane D. hydrogen chloride E. carbon tetrachloride

252. Metallic bonding is best described as

A. the sharing of electron pairs between two atoms B. the electrostatic attraction between cations and a sea of delocalized electrons C. the transfer of electrons from metal to non-metal D. hydrogen bonding between metal atoms E. dipole induced dipole attraction

253. The standard conditions for reporting thermochemical data are

A. 273 K and 1 atm B. 298 K and 1 atm C. 373 K and 1 atm D. 298 K and 10 atm E. 0 K and 1 atm

254. The enthalpy of combustion of a substance is always

A. positive B. negative C. zero D. equal to the enthalpy of formation E. equal to the lattice energy

255. In calorimetry, the heat exchanged is calculated from

A. q = m c delta T B. q = P delta V C. q = nRT D. q = m/c delta T E. q = c delta T / m

256. A bomb calorimeter measures the heat of combustion at constant

A. pressure B. volume C. temperature D. enthalpy E. entropy

257. Internal energy is a state function, which means it depends on

A. the path taken B. only the initial and final states C. the time taken D. the catalyst used E. the container shape

258. A reversible reaction never goes to completion because

A. the catalyst is exhausted B. the reverse reaction becomes appreciable as products accumulate C. the reactants are impure D. the temperature falls E. the pressure drops

259. Raising the temperature of an exothermic reaction at equilibrium

A. shifts it towards the products B. shifts it towards the reactants C. has no effect D. increases Kc E. stops the reaction

260. The pH of pure water at 25 degrees Celsius is

B. 6 C. 7 D. 8 E. 14

261. A larger value of the acid dissociation constant Ka indicates

A. a weaker acid B. a stronger acid C. a neutral solution D. a buffer solution E. a stronger base

262. An aqueous solution of sodium acetate is

A. acidic B. basic C. neutral D. amphoteric E. a buffer on its own only at pH 7

263. The solubility product expression for silver chloride is

A. [Ag+][Cl-] B. [Ag+]/[Cl-] C. [Ag+]2[Cl-] D. [AgCl]/[Ag+][Cl-] E. [Ag+][Cl-]2

264. Dissolving 0.5 mol of solute in enough water to make 250 cm3 of solution gives a molarity of

A. 0.5 M B. 1 M C. 2 M D. 0.125 M E. 5 M

265. The osmotic pressure of a dilute solution is given by

A. pi V = nRT B. pi = nRTV C. pi = RT/nV D. pi V = n/RT E. pi = n/V

266. Molarity changes with temperature but molality does not, because molarity depends on

A. the mass of solute B. the volume of solution C. the mass of solvent D. the number of moles of solute E. the nature of the solute

267. The solubility of most gases in water

A. increases with temperature B. decreases with temperature C. is independent of temperature D. increases with decreasing pressure E. is unaffected by pressure

268. An oxidizing agent is a species that

A. loses electrons B. gains electrons C. donates protons D. increases its own oxidation number E. always contains oxygen

269. The oxidation number of sulphur in sulphuric acid is

A. +2 B. +4 C. +6 D. -2

270. The standard cell potential is calculated as

A. anode potential minus cathode potential B. cathode potential minus anode potential C. the sum of the two reduction potentials D. the average of the two potentials E. always zero

271. The products of the electrolysis of concentrated aqueous sodium chloride using inert electrodes are

A. sodium and chlorine B. hydrogen, chlorine and sodium hydroxide C. oxygen and hydrogen only D. sodium and oxygen E. chlorine and oxygen only

272. The function of the salt bridge in a galvanic cell is to

A. supply electrons to the circuit B. maintain electrical neutrality in the two half cells C. increase the cell voltage D. prevent oxidation E. act as the cathode

273. A nickel cadmium cell is an example of

A. a primary cell B. a secondary cell C. a fuel cell D. a concentration cell E. an electrolytic cell only

274. A hydrogen oxygen fuel cell differs from an ordinary cell in that it

A. stores its reactants internally B. is supplied with reactants continuously from outside C. cannot be recharged and so is useless D. produces no water E. operates without electrodes

275. The unit of the rate constant for a first order reaction is

A. mol dm-3 s-1 B. s-1 C. dm3 mol-1 s-1 D. dm6 mol-2 s-1 E. dimensionless

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