If the temperature is increased, the average speed and kinetic energy of the gas molecules increase. If the volume is held constant, the increased speed of the gas molecules results in more frequent and more forceful collisions with the walls of the container, therefore increasing the pressure
To calculate an energy change for a reaction: add together the bond energies for all the bonds in the reactants - this is the 'energy in' add together the bond energies for all the bonds in the products - this is the 'energy out.
