Looking at how quickly magnesium reacts with dilute hyrdrochloric acid.

- 200 cm
^{3}of 2 mol/dm^{3}hydrochloric acid and deionised water - 10 x 3 cm strips of magnesium
- 100 cm
^{3}beaker, 250 cm^{3}beaker, watch glass, measuring cylinder (25 cm^{3}) - Stop clock

**Method**

- Carefully collect 200 cm
^{3}of hydrochloric acid using the 250cm^{3}beaker, and 10 strips of magnesium using a watch glass. - Using the measuring cylinder, measure out 25 cm
^{3}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:

Volume of hydrochloric acid / cm^{3} | Volume of deionised water / cm^{3} | Time taken for magnesium to disappear / s | Time taken for magnesium to disappear / s | Time taken for magnesium to disappear / s |
---|---|---|---|---|

⠀⠀⠀⠀⠀⠀⠀⠀⠀ | ⠀⠀⠀⠀⠀⠀⠀⠀⠀ | 1 | 2 | Average |

25 | 0 | ⠀⠀⠀⠀⠀⠀⠀⠀⠀ | ⠀⠀⠀⠀⠀⠀⠀⠀⠀ | ⠀⠀⠀⠀⠀⠀⠀⠀⠀ |

20 | 5 | ⠀⠀⠀⠀⠀⠀⠀⠀⠀ | ⠀⠀⠀⠀⠀⠀⠀⠀⠀ | ⠀⠀⠀⠀⠀⠀⠀⠀⠀ |

15 | 10 | ⠀⠀⠀⠀⠀⠀⠀⠀⠀ | ⠀⠀⠀⠀⠀⠀⠀⠀⠀ | ⠀⠀⠀⠀⠀⠀⠀⠀⠀ |

10 | 15 | ⠀⠀⠀⠀⠀⠀⠀⠀⠀ | ⠀⠀⠀⠀⠀⠀⠀⠀⠀ | ⠀⠀⠀⠀⠀⠀⠀⠀⠀ |

5 | 20 | ⠀⠀⠀⠀⠀⠀⠀⠀⠀ | ⠀⠀⠀⠀⠀⠀⠀⠀⠀ | ⠀⠀⠀⠀⠀⠀⠀⠀⠀ |

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

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

Average time / s | Rate / s^{-1} |
---|---|

⠀⠀⠀⠀⠀⠀⠀⠀⠀ | ⠀⠀⠀⠀⠀⠀⠀⠀⠀ |

⠀⠀⠀⠀⠀⠀⠀⠀⠀ | ⠀⠀⠀⠀⠀⠀⠀⠀⠀ |

⠀⠀⠀⠀⠀⠀⠀⠀⠀ | ⠀⠀⠀⠀⠀⠀⠀⠀⠀ |

⠀⠀⠀⠀⠀⠀⠀⠀⠀ | ⠀⠀⠀⠀⠀⠀⠀⠀⠀ |

⠀⠀⠀⠀⠀⠀⠀⠀⠀ | ⠀⠀⠀⠀⠀⠀⠀⠀⠀ |

We can also calculate the percentage of acid used, or, since we know the original concentration of the acid is 2 mol/dm^{3}, we can calculate the concentrate for each experiment:-

Volume of acid / cm^{3} | Percentage acid | Concentration /mol/ dm^{3} |
---|---|---|

25 | 100 | 2.0 |

20 | 80 | 1.6 |

15 | 60 | 1.2 |

10 | 40 | 0.8 |

5 | 20 | 0.4 |

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.