How many sodium atoms are in 3.00 g of sodium dichromate,Na₂Cr₂O₇?

Question

Quizplus · Accepted Answer

First, we need to calculate the molar mass of sodium dichromate: 
Na2Cr2O7 = 2(22.99 g/mol) + 2(51.99 g/mol) + 7(16.00 g/mol) = 261.97 g/mol

Next, we need to calculate the number of moles of sodium dichromate in 3.00 g: 
3.00 g Na2Cr2O7 x (1 mol/261.97 g) = 0.0115 mol Na2Cr2O7

Each formula unit of sodium dichromate contains 2 sodium atoms, so the total number of sodium atoms is: 
2 x 0.0115 mol Na2Cr2O7 x 6.022 x 10^23 atoms/mol = 1.38 x 10^22 sodium atoms

Therefore, the answer is D.

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