How many moles are present in 25 grams of water?

To determine how many moles are present in 25 grams of water, we first need to know the molecular weight of water (H₂O). The molecular weight of water is approximately 18 grams per mole, derived from the atomic weights of hydrogen (approximately 1 g/mol) and oxygen (approximately 16 g/mol).

Using the formula for calculating moles, which is the mass (in grams) divided by the molar mass (in grams/mole), we can find the number of moles in 25 grams of water:

[ \text{Moles of water} = \frac{\text{Mass of water (grams)}}{\text{Molar mass of water (grams/mole)}} ]

[ \text{Moles of water} = \frac{25 \text{ grams}}{18 \text{ grams/mole}} \approx 1.39 \text{ moles} ]

Thus, the calculation confirms that 25 grams of water contains approximately 1.39 moles, making this choice the correct answer. Understanding this relationship between mass and moles using molar mass is essential in fields such as chemistry and biotechnology, where precise measurements and conversions are fundamental to experiments and applications.