Kinetics

Rate of reaction.

HideShow resource information

Rate of chemical reactions

Rate of the reaction- defined as the change in concentration (of any of the reactants of products) with unit time.

(http://simplechemconcepts.com/wp-content/uploads/2008/10/o-level-chemistry-rate-graphs.jpg)

To find the rate of change (c) at a particular instant we draw a tangent to the curve at that time and then find its gradient.

1 of 6

Reaction Rates are measured in:

mol dm-3 s-1

There are 3 ways of recording the rate of reaction:

  • Time how long it takes for the product to disappear,
  • Calculate the volume of gas collected over time,
  • Weigh the loss of gas from the product.

Rate = Change in CONCENTRATION / TIME for change to occur

2 of 6

Rate expression and order of reaction

Rate expression- tells us about the contributions of the species that do affect the reaction rate.

It is an equation that describes how the rate of the reaction at a particular temperature depends on the concentration of species involved in the reaction. It's quite possible that 1 or more of the species that appear in the chemical equation will not appear in the rate expression. This means they do not affect the rate.

Order of reaction- the experimentally determined POWER to which a reactant concentration is raised in a rate equation.

Rate = K (A)p

K = a constant for a particular reaction at a given temperature (the rate constant)

3 of 6

Order of reaction

Zero Order

If doubling (A) has no effect on the rate then the reaction is said to be zero order w.r.t A.

(http://www.avogadro.co.uk/kinetics/graph4.gif)

4 of 6

First order

If doubling (A) doubles the rate then the reaction is said to be first order w.r.t A.

(http://bouman.chem.georgetown.edu/S02/sol1/prob15.gif)

5 of 6

Second order

If doubling (A) increases the rate fur fold then the reaction is said to be second order w.r.t A.

(http://ibchem.com/IB/ibfiles/kinetics/kin_img/2nd_order.gif)

It is unusual for reactions to be mre than second order with respect to any reactant.

to get overall order add all the powers together.

6 of 6

Comments

No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »See all Rates resources »