The ratio a/b (the terms used in van der Waals' equation) has the unit-

1. atm litre mol^-1                           

2. atm dm³ mol^-1

3. dyne cm mol^-1                           

4. All of the above

At relatively high pressure, van der Waals' equation reduces to-

1. PV = RT

2. PV = RT + a/v

3. PV = RT + Pb

4. PV = RT - a/V²

The unit of van der Waals' constant 'a' is:

1. atm litre² mol-²                       

2. dyne cm⁴ mol^-2

3. newton m⁴ mol^-2                     

4. All of the above           

The unit of van der Waals' constant 'b' is :

1. cm³ mol^-1

2. litre mol^-1

3. m³ mol^-1

4. All of these 

At lower temperature, all gases except H₂ and He show:

1. Negative deviation

2. Positive deviation

3. Positive and negative deviation

4. None of the above