Atest tube containing caco₃ is heated until the entire compound decomposes. if the test tube plus calcium carbonate originally weighed 30.08 grams and the loss of mass during the experiment was 4.40 grams, what was the approximate mass of the empty test tube?
a. 20.08 g
b. 21.00 g
c. 24.50 g
d. 25.08 g
e. 25.68 g
can anyone explain this one for me?

What are transitions between a liquid and gas called? identify which way they are transitioning

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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.