3.3 CHAPTER 3. REACTION RATES
Results:- Which of the two solutions is more concentrated, the 1:10 or 1:20 hy-
drochloric acid solution? - In which of the test tubes is the reaction the fastest? Suggest a reason for
this. - How can you measurethe rate of this reaction?
- What is the gas that isgiven off?
- Why was it important that the same length of magnesium ribbon was used
for each reaction?
Conclusions:
The 1:10 solution is more concentrated and thisreaction therefore proceeds
faster. The greater the concentration of the reactants, the faster the rate ofthe re-
action. The rate of the reaction can be measuredby the rate at which hydrogen
gas is produced.Activity: The effect of temperature on reaction rate
- In groups of 4-6, design an experiment that will help you to see the effect
of temperature on the reaction time of 2 cm of magnesium ribbon and 20
ml of vinegar. During your group discussion, you should think about the
following:- What equipment will you need?
- How will you conductthe experiment to makesure that you are able
to compare the results for different temperatures? - How will you record your results?
- What safety precautions will you need to takewhen you carry out
this experiment?
- Present your experiment ideas to the rest ofthe class, and give thema
chance to comment onwhat you have done. - Once you have received feedback, carry out the experiment and record
your results. - What can you conclude from your experiment?
3.3 Reaction rates andcollision theory
ESCAS
It should be clear nowthat the rate of a reaction varies depending ona number of
factors. But how can we explain why reactions take place at different speeds under
different conditions? Why, for example, does anincrease in the surface area of the re-
actants also increase therate of the reaction? One way to explain this is to use collision