How many oxygen atoms are in 3.00 grams of sodium dichromate, na2cr2o7?

The solution is as follows: Convert 3.00 g Na2Cr2O7 into mol. To do this, we must know the molar mass. Molar mass of Na2Cr2O7 is 261.97 g/mol Mol Na2Cr2O7 = (3.00 g Na2Cr2O7)( mol / 261.97 g) = 0.01145 mol In 1 mol of Na2Cr2O7 there are 7 mol of O (oxygen). Therefore: Mol O = 0.01145 mol Na2Cr2O7 (7 mol O/ 1 mol Na2Cr2O7) = 0.08016 mol O In 1 mol of any substance, there are 6.02 x 10^23 atoms Atoms of O = 0.08016 mol O ( 6.02 x 10^23 atoms / mol O) = 4.8257 x 10^22 atoms

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1. and 2. question: in which equation? or i don't understand you, 3. a), 4. c), 5. c), 6. b), 7. d), 8. d) if small number is underlined(behind symbol) , b) if big number is underlined(in front of symbol)9. what is underlined there? 10. c)