1. Determine the molar mass of Na2SO4:

* Na (sodium) has a molar mass of 22.99 g/mol.

* S (sulfur) has a molar mass of 32.06 g/mol.

* O (oxygen) has a molar mass of 16.00 g/mol.

So, the molar mass of Na2SO4 is: (2 * 22.99) + 32.06 + (4 * 16.00) = 142.04 g/mol

2. Determine the moles of sodium (Na) in 0.820 moles of Na2SO4:

* The formula Na2SO4 tells us that there are 2 moles of Na for every 1 mole of Na2SO4.

* Therefore, 0.820 moles of Na2SO4 contains 0.820 moles * 2 = 1.64 moles of Na.

3. Calculate the mass of sodium (Na):

* Multiply the moles of Na by its molar mass: 1.64 moles * 22.99 g/mol = 37.7 g Na

Therefore, there are 37.7 grams of sodium in 0.820 moles of Na2SO4.