Which sources of energy are used by humans to produce electrical energy?

(a) Plants, animals, and fossil fuels
(b) Wind, water, and fossil fuels
(c) Water, wood, and wind
(d) Wind, water, and soil

Which statement best describes the relationship between period and frequency of light waves? a) in wave b the period increases and the frequency decreases from wave a. b) in wave a the period increases and the frequency decreases from wave b. c) in wave b the period is shorter and the frequency is greater than in wave a. d) in wave a the period is shorter and the frequency is greater than in wave b.

How many absorptions would you expect to observe in the 13c nmr spectra of the following molecules? a) 3-chloropentane b) cis-4-methyl-2-pentene

)benzene and toluene form nearly ideal solutions. consider an equimolar solution of benzene and toluene. at 20 °c the vapour pressures of pure benzene and toluene are 9.9 kpa and 2.9 kpa, respectively. the solution is boiled by reducing the external pressure below the vapour pressure. calculate (i) the pressure when boiling begins, (ii) the composition of each component in the vapour, and (iii) the vapour pressure when only a few drops of liquid remain. assume that the rate of vaporization is low enough for the temperature to remain constant at 20 °c.