The molar mass of water (H2O) is 18.015 grams per mole. This means that 1 mole of water contains 18.015 grams of water.

We can use the molar mass of water to calculate the number of grams of hydrogen in 2.08 moles of water.

2.08 moles H2O * (2 moles H / 1 mole H2O) * (1.00794 grams H / 1 mole H) = 4.216 grams H

Therefore, there are 4.216 grams of hydrogen in 2.08 moles of water.