Answer
a) $2.5\times10^{21}$ doz
b) $2.08\times10^{20}$ gross
c) $6\times10^{19}$ reams
d) $4.98\times10^{-2}$ mole
Work Step by Step
a) 1 dozen of any substance contains 12 entities.
Thus, $3.0\times10^{22}$ atoms of Cu contains,
= $\frac{3.0\times10^{22}}{12}$ = $2.5\times10^{21}$ doz of Cu atoms.
b) 1 gross of any substance contains 144 entities.
Thus, $3.0\times10^{22}$ atoms of Cu contains,
= $\frac{3.0\times10^{22}}{144}$ = $2.08\times10^{20}$ gross of Cu atoms.
c) 1 ream of any substance contains 500 entities.
Thus, $3.0\times10^{22}$ atoms of Cu contains,
= $\frac{3.0\times10^{22}}{500}$ = $6\times10^{19}$ reams of Cu atoms.
d) 1 mole of any substance contains $6.022\times10^{23}$ entities.
Thus, $3.0\times10^{22}$ atoms of Cu contains,
= $\frac{3.0\times10^{22}}{6.022\times10^{23}}$ = $4.98\times10^{-2}$ mole of Cu atoms
