How many mg of calcium are present in a 500-mg tablet of calcium carbonate? ?

The molar mass of calcium carbonate is 100 mg/mmol, so the number of moles is:

moles CaCO3 = 500 mg / (100 mg/mmol) = 5 mmol

We see that there is 1 mole of Ca per 1 mole of CaCO3, therefore:

mass Ca = 5 mmol * (40.08 mg/mmol) = 200.22 mg

> b takes place in the gas phase in an isothermal tubular reactor. the feed is one mole of a per one mole of c, an inert. the entering temperature and pressure are 427°c and 10 atm, respectively. the gas constant r = 0.08206 atm · l/mol · k.

answer:

technetium is the most reactive. this is followed by silver. the least reactive out of these three elements is strontium.