If 21.0 l of gas is held at a pressure of 7.80 atm and a temperature of 900.0 k, what will be the volume of the gas if the pressure is decreased to 4.50 atm and temperature decreased to 750.0 k?
a. 30.3 l
b. 32.0 l
c. 35.1 l
d. 36.8 l

When the chemicals iron sulfide (fes) and hydrochloric acid (hcl) are combined, bubbles appear from the mixture. 1. does the appearance of bubbles indicate a physical or chemical change? 2. why do the bubbles indicate this change? 3. what property is this?

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.

How many moles of water are created if 3 moles of hydrogen react completely with excess oxygen?