Reaction Kinetics in Gases

The applet below compares the initial rate of reaction for molecules in the gas phase. The temperature, activation energy and starting concentration of the reactants may all be varied. By clicking on the "Wizard" button, a window appears above the applet to guide students through the process of setting up a reaction to follow.

  • rate of reaction is the change in concentration of a substance divided by the time taken for the change to occur. Substances that are being consumed in a reaction have a negative reaction rate as their concentration is decreasing.

  • initial rate of reaction is the rate of a reaction at the start of the reaction (effectively at time equals zero in the course of the reaction).

The applet allows students to follow one of three possible reactions:

1 A --> C Rate = k[A] Overall first order
2 A + A --> C + C Rate = k[A][A] Overall second order
3 A + B --> C + D Rate = k[A][B] Overall second order

For each of these reactions, students may choose to follow the changes in concentration of reactant or product against time.

  • The initial conditions for the model are for a reaction between two different gases, A and B both at an initial concentration of 0.5

  • The temperature is initially set to 298K and the activation energy is set to 65 kJ.mol-1. These conditions demonstrate that increasing the temperature by 10K will approximately double the initial rate of reaction.

  • Students should be careful when changing the temperature and activation energy variables as these have a very pronounced effect of the reaction rate.

Notes on using the applet:

  • If large changes in reaction rate result from changing the reaction parameters, the chart recorder can be adjusted to record an appropriate trace. Use the "Chart" button to set up the chart recorder for your reaction.


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