\_\_\_\_ grams of 3-Hydroxy propanal ( $\mathrm{MW}=74$ ) must be dehydrated to produce 7.8 g of acrolein $(\mathrm{MW}=56)\left(\mathrm{C}_{3} \mathrm{H}_{4} \mathrm{O}\right)$ if the percentage yield is 64 . (Round off to the nearest integer). [Given: Atomic masses : C: 12.0u, H:1.0u, O:16.0u]

JEE Main · 2021 · 18 Mar 2021 · Shift 1 · Some Basic Concepts of Chemistry

____ grams of 3-Hydroxy propanal (

MW = 74

) must be dehydrated to produce 7.8 g of acrolein

(MW = 56) (C_{3} H_{4} O)

if the percentage yield is 64 .
(Round off to the nearest integer).
[Given: Atomic masses : C: 12.0u, H:1.0u, O:16.0u]

Answer: 16

Dehydration removes one water molecule from each molecule of the hydroxy aldehyde,

C_{3} H_{6} O_{2} \to C_{3} H_{4} O + H_{2} O

, so the two substances stand in a one-to-one mole ratio. The acrolein obtained is

\frac{7.8}{56} = 0.139

mol. Since this is only

64%

of what complete conversion would give, the starting material taken is

\frac{0.139}{0.64} = 0.218

mol. Its mass is

0.218 \times 74 = 16.1

g, so 16 g of 3-hydroxy propanal must be dehydrated.

JEE Main · 2021 · 18 Mar 2021 · Shift 1 · Integer answer