Focusing on Factors that Affect Rates

Chemists are finicky, tinkering types. They usually want to change reaction rates to suit their own needs. What can affect rates, and why Temperature, concentration, and catalysts influence rate as follows  

Some reactants aren t completely dissolved but come in larger, undissolved particles. In these cases, smaller particles lead to faster reactions. Smaller particles expose more surface area, making a greater portion of the particle available for reaction. 

Catalysts increase reaction rates. Catalysts don t themselves become chemically changed, and they don t alter the amount of product a reaction can eventually produce (the yield). An example from early childhood fits here. When you re learning to ride a bike, you might get a push from your parents to help you get going. However, after that push, the pedaling is entirely up to you. Your top speed and end destination are still entirely regulated by your ability to pedal and steer the bike, but that push (the catalyst) helped you get up to speed more quickly. 

If 1 mol of H2 reacts with 1 mol of CI2 to form 2 mol of HCl, does the reaction occur more rapidly in a 5 L vessel or a 10 L vessel Does it occur more rapidly at 273 K or 293 K Why  

The reaction occurs more rapidly in the 5 L vessel because the concentration of reactant molecules is higher when they occupy the smaller volume. At higher concentrations, more collisions occur between reactant molecules. At higher temperatures, pcirticles move with greater energy, which also produces more collisions and collisions of greater force. So the reaction occurs more rapidly at 293 K. 

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