The molar mass of glycerol, C3H8O3, is 92.0 g mol-1 - VCE - SSCE Chemistry - Question 10 - 2022 - Paper 1

To calculate the amount of water required, we need to understand the molecular transformation involved. A triglyceride like tripalmitin will yield glycerol and fatty acids upon hydrolysis. The reaction can be summarized as:

$\text{C}_3\text{H}_8\text{O}_3 + 3\text{H}_2\text{O} \rightarrow \text{C}_{51}\text{H}_{98}\text{O}_6 + 3\text{C} \text{H}_2\text{O}$

From the molar mass of glycerol, the stoichiometry shows that each mole of triglyceride yields a certain number of moles of water. Given that we produce 65.0 g of glycerol, we convert this mass to moles:

$\text{Moles of glycerol} = \frac{65.0 \text{ g}}{92.0 \text{ g mol}^{-1}} \approx 0.707 \text{ mol}$

Each mole of the triglyceride will yield three moles of water. Thus:

$\text{Moles of H}_2\text{O} = 3 \times 0.707 \text{ mol} \approx 2.121 \text{ mol}$

Converting this into grams, we get:

$\text{Mass of H}_2\text{O} = 2.121 \text{ mol} \times 18.0 \text{ g mol}^{-1} \approx 38.2 \text{ g}$