Reaction Pathways - the various directions that a chemical reaction can take place. Higher temperatures tend to make reaction proceed more quickly. Catalyst - substances that increase the rate of a chemical reaction without being changed themselves.
Catalysts lower the activation energy of a chemical reaction making it proceed more quickly.
All chemical reactions are reversible. Some reactions will go to completion. The conversion of such a large quantity of reactants to products that what is unconverted is not noticeable and is unimportant. For equilibrium to occur it is important that none of the reactants or products are allowed to escape. A decrease in pressure will shift this equilibrium to the left.