The relation between pressure exerted by an ideal gas `(p_("ideal"))` and observed pressure `(p_("real"))` is given by the equation,
`p_("ideal")=p_("real")+ (an^(2))/V^(2)`
(i) If pressure is taken in `NM^(-2)`, number of moles in mol and volume in `m^(3)`, calculate the unit of 'a'.
(ii) What will be the unit of 'a' when pressure is in atmosphere and volume in `dm^(3)`?

Explanation

● When pressure is in `Nm^(-2)` and volume in `m^(3)`
`Nm^(-2) = Nm^(-2) + (a mol^(2))/((m^(3))^(2))`
● It total values with the same units are either added or substracte, then the resultant units remain unchanged.
`Nm^(-2) (Nm^(-2) - Nm^(-2)) = (amol^(2))/(m^(6))` or `a = (Nm^(-2)) m^(6) mol^(-2)`
● When pressure is in atmosphere and volume in `dm^(3), a = ((atm)^(2) xx (dm^(3))^(2))/(mol^(2)) = atm^(2) dm^(6) mol^(-2)`