The reaction is carried out over a nickel catalyst in the tubes of a shell$-$and$-$tube reactor. The feed to the reactor contains steam and propane in a $6$:$1$ molar ratio at $125\backslash$deg C$,$ and the products emerge at $800\backslash$deg C$.$ The excess steam in the feed ensures complete consumption of the propane. Heat is added to the reaction mixture by passing a hot gas over the outside of the tubes that contain the catalyst. The heating gas is fed at a rate of $4\mathrm{.}94$ m$3$ per mol of C$3$H$8,$ entering the unit at $1400\backslash$deg C and $1$ atm and leaving at $900\backslash$deg C$.$ The unit as a whole may be considered perfectly insulated from the surroundings. The specific heat capacity of the heating gas can be considered constant and equal to $0\mathrm{.}040$ kJ mol$1$ K$1.$ The mean molar heat capacity of propane between $25$ and $125\backslash$deg C is $84\mathrm{.}15$ kJ kmol$1$ K$1.$