An elementary liquid phase reversible reaction P ↔ Q is carried out in an ideal continuous stirred tank reactor (CSTR) operated at steady state. The rate of consumption of P, -r_P (in mol liter^-1 minute^-1), is given by -r_P=C_P-0.5C_Q where C_P and C_Q are the concentrations (in mol liter^-1) of P and Q, respectively.
The feed contains only the reactant P at a concentration of 1 mol liter^-1, and the conversion of P at the exit of the CSTR is 75% of the equilibrium conversion. Assume that there is no volume change associated with the reaction, and the temperature of the reaction mixture is constant throughout the operation. The space time (in minutes) of the CSTR is _______ (round off to 1 decimal place).