1. Identify the elements and their atomic masses:
* Na (Sodium): 22.99 g/mol
* C (Carbon): 12.01 g/mol
* O (Oxygen): 16.00 g/mol
* H (Hydrogen): 1.01 g/mol
2. Multiply the atomic mass of each element by its subscript in the formula:
* Na: 2 * 22.99 g/mol = 45.98 g/mol
* C: 1 * 12.01 g/mol = 12.01 g/mol
* O: 3 * 16.00 g/mol = 48.00 g/mol
* H: 20 * 1.01 g/mol = 20.20 g/mol
* O (from water): 10 * 16.00 g/mol = 160.00 g/mol
3. Add the masses of all the elements:
45.98 g/mol + 12.01 g/mol + 48.00 g/mol + 20.20 g/mol + 160.00 g/mol = 286.19 g/mol
Therefore, the formula mass of Na₂CO₃·10H₂O is 286.19 g/mol.
