How many oxygen atoms are represented by #MgSO_4 * 7H_2O#? Chemistry The Mole Concept The Mole 1 Answer mason m Dec 20, 2015 #11# Explanation: In #"MgSO"_4#, the number of oxygen atoms is represented by the subscript directly next to the #"O"#. In #"7H"_2"O"#, the coefficient #7# can be multiplied throughout each element in the molecule. #"MgS"color(red)("O"_4)rarr"4 O atoms"# #color(red)("7")"H"_2color(red)("O")rarr"7 O atoms"# There is a total of #4+7=11# oxygen atoms. Answer link Related questions How do you calculate the number of moles from volume? How do you convert grams to mole? Question #258e5 Question #8d48c Why is the mole an important unit to chemists? What's the mole number? How does the mole relate to carbon 12? How does the mole relate to molecules and ions? How do you calculate the moles of a substance? How can I calculate the moles of a solute? See all questions in The Mole Impact of this question 7184 views around the world You can reuse this answer Creative Commons License