Final answer:
To determine the percentage by weight of Na in Na2SO4, we calculate the molar mass of Na2SO4 and then calculate the mass of Na. The percentage by weight of Na is 32.37%.
Step-by-step explanation:
To determine the percentage by weight of Na in Na2SO4, we need to calculate the molar mass of Na2SO4 and then determine the mass of Na in that compound. The molar mass of Na2SO4 is calculated by adding the atomic masses of Na, S, and 4 O atoms, which gives us: (2 x 22.99 g/mol) + 32.07 g/mol + (4 x 16.00 g/mol) = 142.04 g/mol. From the molar mass, we can see that Na contributes 45.98 g/mol (2 x 22.99 g/mol) to the overall mass of Na2SO4. Finally, we can calculate the percentage by weight of Na by dividing the mass of Na by the molar mass of Na2SO4 and multiplying by 100: (45.98 g/mol / 142.04 g/mol) x 100% = 32.37%.