At the end of two half-lives, what fraction of the atoms has not decayed?

How many moles is 14.5 cm^3 of platinum? the density of platinum is 21.45 g/cm^3.

Salt in oceans comes from and of rocks

Scientists are often interested in knowing the molar heat of combustion – the heat released during the combustion of one mole of a substance. use the periodic table to find molar masses. how many moles of ethanol are present in the sample?