Which of the following statements about nucleophilic aromatic substitution is true? multiple choice a. in the addition-elimination mechanism, the aromatic ring first accepts a pair of electrons from a nucleophile to form a cationic intermediate. b. for the elimination-addition pathway, the nucleophile becomes attached only at the site bearing the leaving group. c. for the addition-elimination pathway, the nucleophile may become attached either at the site bearing the leaving group or at the site bearing the ortho hydrogen atom. d. the elimination-addition mechanism is not as common as the addition-elimination mechanism.

If a gas has an initial pressure of 101kpa and a volume of 10l, then it expands to a volume of 20l, what is the new pressure?

Tooth enamel consists mainly of the mineral calcium hydroxyapatite, ca_10(po_4)_6(oh)_2. trace elements in teeth of archaeological specimens provide anthropologist with clues about diet and diseases of ancient people. students at hamline university measured strontium in enamel from extracted wisdom teeth by atomic absorption spectroscopy. solutions with a constant total volume of 10.0 ml contained 0.726 mg of dissolved tooth enamel plus variable concentrations of added sr. added sr find the concentration of sr in the 10 ml sample solution in parts per billion = ng/ml. find the concentration of sr in tooth enamel in parts per million = mu g/g.

Adirect relationship can be represented by: a curve a pie chart