Answer
a) 7.63 mole Pb
b) $4.67 \times 10^{-2}$ mole He
c) 1.31 mole K
d) $7.31 \times 10^{-3}$ mole Ca
Work Step by Step
1 mole of a substance contains $6.022 \times 10^{23}$ atoms.
*** to convert atoms into moles we divide the number of moles by $6.022 \times 10^{23}$
a) $4.6 \times 10^{24}$ Pb atoms = $\frac{4.6 \times 10^{24} atoms}{6.022 \times 10^{23}}$ = 7.63 mole Pb
b) $2.87 \times 10^{22}$ He atoms = $\frac{2.87 \times 10^{22} atoms}{6.022 \times 10^{23}}$ = $4.67 \times 10^{-2}$ mole He
c) $7.9 \times 10^{23}$ K atoms = $\frac{7.9 \times 10^{23} atoms}{6.022 \times 10^{23}}$ = 1.31 mole K
d) $4.41 \times 10^{21}$ Ca atoms = $\frac{4.41 \times 10^{21} atoms}{6.022 \times 10^{23}}$ = $7.31 \times 10^{-3}$ mole Ca
