How many oxygen atoms are there in 5.00 g of sodium dichromate,Na₂Cr₂O₇?

Question

Quizplus · Accepted Answer

1 mole of Na2Cr2O7 contains 17 moles of oxygen atoms (from the formula).

The molar mass of Na2Cr2O7 is: 
2(22.99 g/mol Na) + 2(52.00 g/mol Cr) + 7(16.00 g/mol O) = 294.18 g/mol

Using this information, we can set up the following dimensional analysis:

5.00 g Na2Cr2O7 x (1 mole Na2Cr2O7 / 294.18 g) x (17 moles O / 1 mole Na2Cr2O7) x (6.022 x 10^23 atoms / 1 mole) = 8.04 x 10^22 oxygen atoms

Therefore, the answer is D, 8.04 × 10^22 oxygen atoms.

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