Reaction rates. S2: Chemical reactions effect of concentration on reaction rates

1. Rates of reactions
2P9: Monday 22nd
November

2. Experiment
• Aim: To see what effect
concentration has on the speed of a
chemical reaction.

3. What is concentration?
High concentration Low concentration

4. Method
• Collect: 2 bottles of Hydrochloric acid (different
concentrations), 2 small beakers, balance, Calcium
Carbonate chips and filter paper
• Measure 25ml of Hydrochloric acid (low
concentration) into one beaker
• Measure 25ml of Hydrochloric Acid (high
concentration) into the other beaker
• Weigh out 2 separate quantities of Calcium
Carbonate chips, each weighing 2g
• Add one sample of chips into each beaker of acid
• Observe and record what happens in your notebooks

5. Results:
The calcium carbonate reacted
faster with the concentrated
Hydrochloric acid.
WHY???

6. Conclusion
• In the acid with the high concentration,
there were more particles available to
react which resulted in a faster
reaction
• This result suggests that the higher the
concentration, the faster the reaction

7. Experiment
• Aim: To see what effect the
temperature has on the speed of a
chemical reaction.

8. Method
1. Measure 20ml of Sodium thiosulphate solution into a small
beaker using a measuring cylinder.
2. Mark a “X” on a piece of filter paper.
3. Place the beaker on the filter paper.
4. Measure 1ml of Hydrochloric acid and add it to the beaker –
START THE STOPWATCH!
5. Stop the watch when the cross disappears.
6. Wash the solution down the sink and measure out another 20ml
of Sodium thiosulphate.
7. Place the beaker in a hot water bath for about 2 minutes. Then
repeat steps 2-5

9. Results
Reaction temperature (degrees Celsius) Reaction time (seconds)
22o
C
55o
C

10. Conclusion
• The cross was obscured more quickly in
the experiment performed at the higher
temperature
• Therefore the experiment performed at
the higher temperature gave the fastest
reaction time
• This suggests that the higher the
temperature, the faster the speed of the
reaction

11. Explanation
• Increasing the temperature of a
reaction gives the particles more energy
which allows the particles to move
around more quickly
• This in turn increases the number of
collisions of particles, and therefore
increases the speed of reaction

12. Speed of reactions
The speed of a chemical reaction can be influenced by:
1.Particle size:
• Decreasing particle size (increasing surface area) 
Increases the speed of reaction
1.Concentration:
1. Increasing concentration  Increases the speed of reaction
•Temperature:
• Increasing concentration  Increases the speed of reaction