PRELIMINARY COURSE ASSESSMENT

CHEMISTRY:

REACTION RATES

PART A

PART B

PART C

BIBLIOGRAPHY

TEAM MEMBERS

GUEST BOOK

ABOUT

Page: 4 of 10 (* currently answering part (a) )

Every reaction requires a certain minimum energy for the reaction to occur, it is called activation energy, Ea, and is expressed in kJ.

The CO + NO₂ mixture from Example 1 has an Ea = 134 kJ.  This means that the colliding molecules must have a total Ea of 134 kJ/mol if they are to react.

Where,  DH > 0.

Where,  DH < 0.

Ea depends upon the nature of the reaction. Fast reactions usually have a small Ea; those with a large Ea usually proceed slowly. It is independent of temperature and concentrations.

 Concentration

 As the concentration of a reactant is increased, generally the rate of a reaction also increases. This is due to the increase in the number of successful collisions between reacting particles.

The collision theory describes the way temperature; concentration and surface area of the solid reactant affects the rate of reaction due to the collisions present between particles. Particles react when they collide with sufficient energy. At a higher temperature collisions are more frequent since more energy is supplied to the particles that causes particles to move faster and therefore obtain higher momentum and kinetic energy.

 While at higher concentrations the collisions are again more frequently, as there are more reactant particles in the liquid. Increased surface area of the solid again increases the frequency of collision between reacting particles, as the liquid reactant has greater contact with the solid one. Adding a catalyst can also increase rate of reaction.

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