Comparison of the single-point and multipoint methods

The error introduced by the single-point method can be evaluated by examining the difference between as determined by equations (5.3) and 

Subtracting equation (5.3) from (5.5) and dividing by equation (5.5) gives the relative error associated with the single-point method, that is. 

The subscripts mp and sp above, refer to the multi- and single-point methods. 

The last column of Table 5.1 is established by substituting equation Table 5.1 Relative error using the single-point method at various relative pressures 

The surprising relationship above shows that when a single-point analysis is made using the relative pressure which would give monolayer coverage according to the multipoint theory, the relative error will be equal to the relative pressure employed and also, according to equation (4.44), will be equal to the fraction of surface unoccupied. 

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