Final answer:
The calculation is nearly correct, using a molar mass of 18.02 g/mol. For precise calculations, the molar mass of H2O should be 18.015 g/mol, which still results in approximately 2.55 moles of H2O.
Step-by-step explanation:
To determine if the calculation of moles of H2O (water) is correct, one must first verify the molar mass used in the conversion from grams to moles. The correct molar mass of water is 18.015 g/mol, considering the mass of two hydrogen atoms (2 x 1.008 g/mol) and one oxygen atom (15.999 g/mol).
The student used the value of 18.02 g/mol for the molar mass, which is sufficiently close, given that molar masses are often rounded to two decimal places for practical calculations. Therefore, the calculation is nearly correct but can be fine-tuned by using the more precise molar mass of 18.015 g/mol. If we use the exact value, the calculation should be 45.9 grams H2O times 1 mole H2O over 18.015 grams H2O, which equals approximately 2.55 moles of H2O.