Question

_________ grams of 3-Hydroxy propanal (MW = 74) must be dehydrated to produce 7.8 g of acrolein (MW = 56) if the percentage yield is 64. (Round off to the Nearest Integer).

Hint:

Yield factor: $\text{Required Amount} = \frac{\text{Theoretical Stoichiometric Amount}}{% \text{Yield}}$.

Answer 1

Correct Answer: 16

Step 1: Reaction: $HO-CH_2-CH_2-CHO \xrightarrow{-H_2O} CH_2=CH-CHO$ (Acrolein).
Step 2: Stoichiometry is 1:1.
Step 3: Theoretical moles of acrolein needed $= \frac{\text{Actual moles}}{\text{Yield}} = \frac{7.8/56}{0.64} \approx 0.2176$ mol.
Step 4: Mass of 3-Hydroxy propanal $= 0.2176 \times 74 \approx 16.1$ g. The nearest integer is 16.