1. Balance the following equations: (a) K + MgBr2 KBr + Mg
(b) CH4 + O2 CO2 + H2O
[Total: 2]

2. Write a balanced chemical equation for the following,
including state symbols:
a) An aqueous solution of barium chloride reacts with a dilute solution
sodium sulphate to from a precipitate of barium sulphate
and an aqueous solution of sodium chloride.
b) Write the ionic equation for the reaction in 2 (a).

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.