NCERT Class XI Chemistry States of Matter Solutions

Question : 11

Total: 23

A student forgot to add the reaction mixture to the round bottomed flask at 27°C but instead he/she placed the flask on the flame. After a lapse of time, he realized his mistake, and using a pyrometer he found the temperature of the flask was 477°C. What fraction of air would have been expelled out?

Solution:

Suppose the number of moles of gas present at 27°C in flask of volume V at pressure P is n1, then assuming ideal gas behaviour,
PV = n1R × 300 ...(1)
Suppose n2 = number of moles at 477°C, then PV = n2R × 750 ...(2)
From equation (1) and equation (2), we get n2 =

300

750

×n1 = 0.4 n1
So, (1 - 0.4) × 100% is expelled out i.e. 60%..

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