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  Van der Waal's equation | 1st year chemistry unit 3 Why the volume correction is done by van der Waal? Ans. Actual volume of gas molecules is not negligible as compared to the total volume of vessel. Therefore, Van der Waal corrected the volume factor in general gas equation. So, excluded volume is subtracted from total volume of vessel to get the free volume available for gas molecules.                                       V free = V vessel – b (excluded volume) Why the pressure correction is done by Van der Waal? Ans. Forces of attraction present between molecules of real gas. Therefore, Van der Waal corrected the pressure correction in general gas equation. Lessened pressure is subtracted from ideal pressure to get the observed pressure.        ...

  Non ideal behaviour of gases | 1st year chemistry chapter 3 Gases deviate more from the general gas equation at 0 o C and deviate to less extent at 100 o C. Why? Ans. General gas equation is for ideal gases (which have no forces of attraction). At 0 o C molecules are close to each other and have strong attraction, while at 100 o C molecules are far away from each other and have very weak attractions. Therefore, Gases deviate more from the general gas equation at 0 o C and deviate to less extent at 100 o C. Hydrogen and helium are ideal at room temperature, but SO 2 and Cl 2 are non-ideal. How do you explain it? Ans. Molecules of hydrogen and helium are very far away and have no force of attraction at room temperature. While molecules of SO 2 and Cl 2 are very close and have force of attraction at room temperature. Therefore, Hydrogen and helium are ideal at room temperature, but SO 2 and Cl 2 are non-ideal. Why the gases deviate from ideal behaviour at high pressure ...

  Liquefaction of gases | first year chemistry chapter 3 Define critical temperature. Give examples. Ans. The temperature of a gas above which a gas cannot be liquefied, no matter how great the  pressure is applied, is called  critical temperature. It is denoted by T c . Examples: Gas Critical temperature ( o C) O 2 -118.7 NH 3 132.4 CO 2 31.1 Define critical pressure. Give examples. Ans. It is the minimum pressure which is required to liquefy a gas at its critical temperature. It is denoted by P c . Examples:  Gas Critical pressure (atm) O 2 49.7 NH 3 111.5 CO 2 73.0 Define critical volume. Give examples. Ans. The volume which is occupied by one mole of a gas at critical temperature and critical pressure is called critical volume. It is denoted by V c. Examples: The critical volu...