Rate of reaction
How fast a reaction happens. It goes up with higher temperature, higher concentration, larger surface area or a catalyst.
Last updated
Analogy
More people in a smaller room means more bumps. Reactions need particles to collide.
Example
Mean rate = amount made / time60 cm3 of gas in 30 sRate = 60 / 30 = 2 cm3/s
In practice
Powdered chalk reacts with acid faster than a lump because more surface is exposed.
Practice
Flashcards
- Give two ways to increase the rate of a reaction.Raise the temperature or increase the concentration. A larger surface area or a catalyst also works.
Interview questions
- Explain, using particles, why increasing the temperature increases the rate of a reaction.
- Particles move faster
- More frequent collisions
- A larger proportion of collisions have enough energy
- So more successful collisions each second
Questions people ask
What is collision theory?
For a reaction to happen, particles must collide with enough energy. The minimum energy needed is the activation energy. Anything that makes collisions more frequent or more energetic, such as a higher temperature or concentration, speeds up the reaction. Particles that collide without enough energy simply bounce apart.
How do you measure the rate of a reaction that makes a gas?
Collect the gas in a gas syringe and record the volume at regular times. Or put the flask on a balance and record the mass lost as the gas escapes. Plot a graph. A steeper line shows a faster rate, and the line flattens when the reaction stops.