The molecular weight of water is 18.0154. One mole of water weighs _______ grams. Naim 00:06 Small Molecules and the Chemistry of Life The molecular weight of water is 18.0154. One mole of water weighs _______ grams. a. 9 b. 18 c. 20 d. 36.031 e. 6.023 × 1023 Answer: B Learn More : Share this Share on FacebookTweet on TwitterPlus on Google+