Vanderwaals Constant-

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source : askIITians

The vanderwaals constant are ‘a’ and ‘b’. These are characteristics of each gas and always depend on the nature of gas.

## units of vanderwaals constant ‘a’ and ‘b’ –

*(A) The pressure correction in vanderwaals equation is an ^{2}/V^{2}*

*so,*

* an ^{2}/V^{2} = unit of P*

*a = PV ^{2}/n^{2}*

a= Pressure X (volume)^{2}/(mole)^{2}

*unit of a = atmosphere . litre ^{2}/mole^{2}*

*unit of a = atmosphere . litre ^{2} .mole^{-2}*

*OR*

*atmosphere. dm ^{6}. mole^{-2}*

*of unit of P = Newton/meter ^{2} = N/m^{2} or Nm^{-2} (SI unit)*

*V = meter ^{3}*

*unit of a = newton meter ^{-2}.meter^{6}/mole^{2} = Nm^{-2}m^{6}/mole^{2}*

*unit of a = Nm ^{4} mole^{-2}*

*B) Effective volume for ‘n’ moles of gas is ‘ nb’.*

*V= nb*

*b=V/n *

b= Volume / mole

*Unit of b = litre/mole = litre mole ^{-1} OR m^{3} mole^{-1} (SI unit)*