Here's how to calculate the grams in one mole of H₂O:

1. Determine the molar mass of each element:

* Hydrogen (H): 1.008 g/mol

* Oxygen (O): 15.999 g/mol

2. Calculate the molar mass of H₂O:

* H₂: 2 * 1.008 g/mol = 2.016 g/mol

* O: 15.999 g/mol

* Total: 2.016 g/mol + 15.999 g/mol = 18.015 g/mol

Therefore, there are 18.015 grams in one mole of H₂O.