Question 3.5: Calcium is the most abundant metal in the human body. A typi...
Calcium is the most abundant metal in the human body. A typical human body contains roughly 30 moles of calcium. Determine (a) the number of Ca atoms in 30.00 moles of calcium and (b) the number of moles of calcium in a sample containing 1.00 × 1020 Ca atoms.
Strategy Use Avogadro’s number to convert from moles to atoms and from atoms to moles.
Setup When the number of moles is known, we multiply by Avogadro’s number to convert to atoms. When the number of atoms is known, we divide by Avogadro’s number to convert to moles.
(a) 30.00 \cancel{mol Ca} × \frac{6.022 × 10^{23} Ca atoms}{1 \cancel{mol Ca}} = 1.807 × 10^{25} Ca atoms
(b) 1.00 × 10^{20} \cancel{Ca atoms} × \frac{1 mol Ca}{6.022 × 10^{23} \cancel{Ca atoms}} = 1.66 × 10^{-4} mol Ca