Final answer:
The weight of 0.338 moles of methanol with a molar mass of 32 g/mol and purity of 0.79 is 8.545 grams, which is closest to the provided option D (8.491 g).
Step-by-step explanation:
To calculate the weight of 0.338 moles of methanol with a molar mass of 32 g/mol and a purity of 0.79, you follow these steps:
First, calculate the weight of the pure methanol by multiplying the number of moles by the molar mass: weight (pure) = 0.338 moles × 32 g/mol = 10.816 g.
Then, take into account the purity of the methanol by multiplying the weight of the pure methanol by the purity: weight (actual) = 10.816 g × 0.79 = 8.54464 g.
After rounding this to the nearest thousandth, you get 8.545 g, which can be approximated to 8.545 grams of methanol when considering purity, which is closest to option D (8.491 g).