Multiple choice

When the mixture of two immicible liquids (water and nitrobenzene) boils at 372 K and the vapour pressure at this temperature are $97.7 kPa (H_{2}O $and $3.6 kPa$ $(C_{6} H_{5}NO_2]). $Calculate the weight per of nitrobezene in the vapour.

  1. $10.55$
  2. $20.11$
  3. $30.84$
  4. $61.68$
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B Correct answer
Explanation

For immiscible liquids, the vapour contains amounts proportional to their partial pressures. Using molecular masses 18 for water and 123 for nitrobenzene, the nitrobenzene mass percentage is 3.6 × 123 divided by (97.7 × 18 + 3.6 × 123), multiplied by 100, which is about 20.11%.

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