Question

Question 5.11 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?

Class XI States of Matter Page 153

Answer 1

concept :- if pressure remains constant .
then, apply Charles' law
$e.g., \frac{V_1}{T_1}=\frac{V_2}{T_2}$
Let volume of the air in flask = V cm³ at T = 27°C or 300K
Now, V1 = V cm³ , T1 = 300K, T2 = 477°C or 750K
now, use Charles' law ,
$e.g., \frac{V_1}{T_1}=\frac{V_2}{T_2}$
V/300 = V2/750
V2 = (750/300)V = 2.5V
volume expelled = final volume- initial volume
= 2.5 V - V = 1.5V

now, fraction of air expelled = volume expelled/final volume = 1.5V/2.5V = 3/5 = 0.6