Apparatus
- Top pan balance
- Measuring cylinder
- Electronic timer
- Three pieces of magnesium strip
- The following concentrations of acid: 0.5M, 1.0M, 1.5M, 2.0M, 2.5M, and 3.0M
- Safety goggles
Fair Test
Use the same volume of acid for each test. Use the same mass of magnesium for each test also because if the lengths of the Magnesium are different, then the surface area and the mass of Magnesium will be affected. This will produce more than one variable, which will make the results less accurate. Keep the temperature of acid the same. Start the timer as soon as the acid is poured onto the magnesium. The beaker must be washed out after each experiment because if it is not then there will be still reactants in the beaker like the Hydrochloric acid.
Method
- Put on the safety goggles.
- Collect the equipment.
- Cut the magnesium strip in half and weigh each piece. Ensure all the pieces of magnesium are the same length, (0.05g)
- Put the 10cm of acid in the measuring cylinder.
- Place the magnesium strip in a small beaker.
- Pour in the hydrochloric acid into the beaker and start the timer as soon as the acid is poured in.
- Stop the timer as soon as the Hydrochloric acid and Magnesium stops reacting. The Magnesium will have stopped reacting when there is no fizzing.
- Repeat the test again three times for each concentration of acid, 0.5, 1.0,. 2.0M, 2.5M and 3.0M.
Table 1 showing the rate of reaction for different concentrations of acids
What my results mean?
The findings of my experiment confirm my prediction. The results showed that as the concentration of acid increases, the time taken for the reaction increases. The acid concentration of 0.5 Molar was the longest in duration where a time of 3.66 seconds whereas the 3.0 Molar concentration of the acid took the shortest time with an average of 24 seconds. This implies that there is an inverse relationship between the concentration of acid and the time taken for the reaction to occur. The rate of reaction increased with increase in the concentration of the acid. The rates of reaction for the concentrations 0.5M, 1.0M, 1.5M, 2.0M, 2.5M, AMD 3.0M where 0.0027, 0.036, 0.012, 0.014, 0.025 AND 0.042 Mols respectively. This suggests that the rate of reaction has positive correlation with concentration of the acid. From the graph, it does not look to clear if the relationship was linear or a curve. The observations above could best be explained by the collision theory. According to the collision theory, the more concentrated the substance (acid) is the greater the number of particles/molecules that will be involved in the collision. This means that the frequency of collision will increase and hence the greater the chances of successful collision which ultimately leads to an increase in the rate of reaction and the formation of more molecules that are involved in the collision. This results in a very slow reaction and a very low rate of reaction. On the contrary, the 3.0M concentration of acid, more particles are involved in the collision increases the frequency of collision and increasing the chances of more successful collision. Therefore, a faster rate of reaction and a small duration of reaction time. See (Table 1) and (Fig 1)
Evaluation
I think my results could have been more accurate as I may have forgotten to rinse out the beaker cylinder between testing different concentrations. Another reason may have been that my measuring wasn’t accurate enough. I may have used too much or too little acid concentration into the cylinder. The experiment could have been repeated using a wider range surface of areas. It could also be repeated using a different metal, other than Magnesium to make sure that the conclusion does not only refer to Magnesium. If the acid used was changed, the conclusion would not just apply to Hydrochloric acid. I would also use a gas syringe to measure the volume of gas.
