Answer
There are $ 5.37 \times 10^{23} atoms$ of oxygen in 20g of Epsom salt.
Work Step by Step
As we calculated in the last exercise, there are 0.081 moles of Epsom salt in 20g.
The chemical formula for Epsom salt is $MgSO_4 ∙7H_2O$,; therefore, we have 4 + 7 = 11 moles of oxygen for each mole of this compound.
$0.081 moles (Epsom$ $Salt) \times \frac{11 moles (O)}{1 mole (Epsom-Salt )} = 0.891 moles (O)$
$0.891 moles \times \frac{6.022 \times 10^{23} atoms}{1 mol} = 5.37 \times 10^{23} atoms$
