Final answer:
The mass of a single water molecule is approximated to be 2.99 × 10^-23 grams, using its molar mass of 18.015 g/mol and Avogadro's number, which indicates the number of molecules in one mole.
Step-by-step explanation:
To calculate the mass in grams of a single water molecule, we first look at the molar mass of water (H2O) which is 18.015 g/mol. This is because one mole (6.022 × 1023 entities) of water molecules weighs 18.015 grams. The mass of a single water molecule is therefore:
(1 molecule / 6.022 × 1023 molecules/mol) × 18.015 g/mol
Performing the calculation, we find the mass of a single water molecule to be approximately:
(1 / 6.022 × 1023) × 18.015 g
= 2.99 × 10-23 g
The mass of a single water molecule is 2.99 × 10-23 grams.