How will changing the concentration of hydrochloric acid change the rate at which it reacts with magnesium?

Prediction:

I predict that the higher the acid concentration is, the faster the rate of reaction will be. The lower the acid concentration, the slower the reaction will be. I think this because when the acid is concentrated, there are more particles of acid between the water particles, so therefore the acid particles are more likely to get to the magnesium particles and there will be more collisions per second. The acid particles would react faster with the magnesium particles therefore the rate of reaction will be faster.

Equipment:

• Measuring cylinder
• Hydrochloric Acid
• Water
• Magnesium
• Thermometer
• Beaker
• Stopwatch

Diagram:

Method:

• Collect equipment.
• Measure 4cm³ of hydrochloric acid in a measuring cylinder. Use a thermometer to test the temperature of the acid. Write it down and make sure all the other acid used is the same temperature by measuring it each time you use it. If it is not heat it up using a Bunsen burner or cool it by putting it in the fridge.
• Measure 36cm³ of water. Use a thermometer to test the temperature of the water. Write it down and make sure all the other water used is the same temperature by measuring it each time you use it. If it is not, heat it up using a Bunsen burner or cool it by putting it in the fridge.
• Put the acid and water together in the same beaker.
• Weigh 4 pieces of magnesium. Write down the mass and make sure that the next pieces of magnesium that you use are all the same mass.
• Add these 4 pieces of magnesium to the acid and water solution.
• As soon as you have added the pieces of magnesium start the stop watch. Watch the reaction, when all of the magnesium has dissolved it has stopped reacting and stop the stop watch.
• Record how long it took to react.
• Repeat the same experiment for different concentrations of acid. (See results table for measurements of acid and water.)

Results:

Conclusion:

My prediction was right and the results show that the higher the acid concentration, the faster the rate of reaction is. The lower the acid concentration, the slower the rate of reaction is. This is because when the acid is more concentrated there are more particles of acid between the particles of water, therefore the particles of acid are more likely to hit and react with the magnesium particles and there are more collisions per second and the magnesium will react faster. I did not have to change my plan for the experiment.

Evaluation:

If I did this experiment again I would put the experiments in a water bath to make sure they were all the right temperatures. I would make sure that all the pieces of magnesium were the same size. I would use a more accurate measuring cylinder to measure the amount of water and acid. I would use a computer to start the stop watch and finish it when the magnesium stops reacting. This is because I stopped the stop watch when I thought the magnesium had stopped reacting but it could have still been reacting and I just did not see.