Write about van der Waal's equation.
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The relationship for these variables, P V = n R T, where R is known as the gas constant, is called the ideal gas law or equation of state.
To account for the volume that a real gas molecule takes up, the van der Waals equation replaces V in the ideal gas law with (V-b), where b is the volume per mole that is occupied by the molecules. This leads to:
{\displaystyle P(V_{m}-b)=RT}
The second modification made to the ideal gas law accounts for the fact that gas molecules do in fact attract each other and that real gases are therefore more compressible than ideal gases. Van der Waals provided for intermolecular attraction by adding to the observed pressure P in the equation of state a term {\displaystyle a/V_{m}^{2}, where a is a constant whose value depends on the gas. The van der Waals equation is therefore written as:
{\displaystyle (P+a/V_{m}^{2})(V_{m}-b)=RT}
and can also be written as
{\displaystyle (P+an^{2}/V^{2})(V-nb)=nRT}
where Vm is the molar volume of the gas, R is the universal gas constant, T is temperature, Pis pressure, and V is volume. When the molar volume Vm is large, b becomes negligible in comparison with Vm, a/Vm2 becomes negligible with respect to P, and the van der Waals equation reduces to the ideal gas law, PVm=RT.
To account for the volume that a real gas molecule takes up, the van der Waals equation replaces V in the ideal gas law with (V-b), where b is the volume per mole that is occupied by the molecules. This leads to:
{\displaystyle P(V_{m}-b)=RT}
The second modification made to the ideal gas law accounts for the fact that gas molecules do in fact attract each other and that real gases are therefore more compressible than ideal gases. Van der Waals provided for intermolecular attraction by adding to the observed pressure P in the equation of state a term {\displaystyle a/V_{m}^{2}, where a is a constant whose value depends on the gas. The van der Waals equation is therefore written as:
{\displaystyle (P+a/V_{m}^{2})(V_{m}-b)=RT}
and can also be written as
{\displaystyle (P+an^{2}/V^{2})(V-nb)=nRT}
where Vm is the molar volume of the gas, R is the universal gas constant, T is temperature, Pis pressure, and V is volume. When the molar volume Vm is large, b becomes negligible in comparison with Vm, a/Vm2 becomes negligible with respect to P, and the van der Waals equation reduces to the ideal gas law, PVm=RT.
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