A large piece of iron was reacted with an acid. What would happen to the rate of the reaction had the large piece been finely divided into smaller pieces?

It will decrease because the reactant particles are moved farther apart.
It will increase because the reactant particles are brought closer together.
It will decrease because larger particles provide more surface area to react.
It will increase because smaller particles provide more surface area to react.

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.