How many moles of aluminum ions are present in 0.34 moles of Al2(SO4)3?

Express the number of moles to two significant figures.

Iknow the answer to 13 is b and 14 is d. i just need to know why the correct answers are correct

At 300 mm hg, a gas has a volume of 380 l, what is the volume at standard 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.