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How do the vanderwaals constants a, b vary for different gases? The value of a is higher for ethane than that for ammonia?

How do the vanderwaals constants a, b vary for different gases?
The value of a is higher for ethane than that for ammonia?

Grade:12

4 Answers

Pankaj
askIITians Faculty 131 Points
9 years ago
Hello Student
Vander Waals constant for attraction (a) and volume (b) are characteristic for a given gas. Some salient feature of a & b are:

1. For a given gas Vander Waal’s constant of attraction ‘a’ is always greater than Vander Waals constant of volume (b).

2. The gas having higher value of ‘a’ can be liquefied easily and therefore H2& He are not liquefied easily.

3. The units of a = litre2atm mole–2& that of b = litre mole–1

4. The numerical values of a & b are in the order of 10–1to 10–2& 10–2to 10–4respectively.

5. Higher is the value of ‘a’ for a given gas, easier is the liquefaction.

Himaja
40 Points
9 years ago
How do they vary for different gases? Eg:Why the the value of a is greater for C2H6 than for NH3 
Pankaj
askIITians Faculty 131 Points
8 years ago
Extent of attraction and repulsion depends on the nature of molecule. So, different molecules have different values of a and b.
Himaja
40 Points
8 years ago
a actually depends on te extent of forces of attraction b/w te molecules in a gas. these  forces are more in ammonia (H-Bonds) tan in ethane.But the actual a value is more for etane.
 

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