4. Investigate the rate of reaction

Question 1

Investigate the rate of reaction

Answer 1

Apparatus and chemicals
200 cm3 of 2 mol/dm3 hydrochloric acid and deionised water
10 x 3 cm strips of magnesium
100 cm3 beaker, 250 cm3 beaker, watch glass, measuring cylinder (25 cm3)
Stop clock
Method

Carefully collect 200 cm3 of hydrochloric acid using the 250cm3 beaker, and 10 strips of magnesium using a watch glass.
Using the measuring cylinder, measure out 25 cm3 of hydrochloric acid and add to the small beaker. Remember to use the measuring cylinder accurately.
Drop the piece of magnesium ribbon into the beaker and start the stop watch, swirl once to ensure the magnesium is fully coated in the acid. Stop the watch when all the magnesium disappears.
Repeat the experiment to ensure reliability of results.
Repeat steps 2-4 except using a total of five different volumes of acid and water to ensure different concentrations of acid. The proportions you need to use are given in the results table:

In this experiment we can use the times to calculate an approximate value for the rate of each reaction by using the formula:-

rate = 1/time

Using your average times calculate the rate of reaction for each experiment:-

We can also calculate the percentage of acid used, or, since we know the original concentration of the acid is 2 mol/dm3, we can calculate the concentrate for each experiment:-

Finally, we can plot a graph of our Independent Variable (x-axis) against our Dependent Variable (y-axis). Your Independent Variable will be either % Acid, or Concentration. Your Dependent Variable will either be time or rate. Your teacher will instruct you on which to use.