All of these precautions will make my final results more reliable and keep anomalies at a minimum so thus make the entire investigation more successful.
Prediction:
I predict that the stronger the concentration the faster the reaction rate will be. I’ve based my theory on the collision theory: ‘All atoms need to collide with a minimal amount of energy to react’ (A.Q.A Science). This means that with a stronger solution there are more particles to react with each other and there’s a greater chance they’ll collide so the reaction rate will be quicker because if the frequency of collisions is increased the rate of reaction will increase. This means that my graph that I’ll draw up in analysis will have positive correlation, and will probably be curved as the increase in rate of reaction will not be exactly the same as the concentration is increased.
Safety:
The main safety issues are the liquids coming in contact with my eyes and the hydrochloric acid coming in contact with my skin. That’s why I’ll be wearing safety goggles and paying attention at all times also I’ll spend extra care when I’m directly using the hydrochloric acid.
Apparatus:
- 1 thermometer – To make sure liquids are at the same temperature to keep test fair and make results more accurate.
- 5 beakers – To hold the liquids in.
- 6 measuring cylinders – 1 to measure hydrochloric acid, 1 to measure the distilled water and 4 to measure the Sodium Thiosulphate.
- 3 conical flask - 1 to hold hydrochloric acid, 1 to hold the distilled water and one to hold the Sodium Thiosulphate.
- 1 stopwatch – To measure time taken for reaction to occur.
- X paper – To aid the decision of when a reaction has occurred.
- 1 pair of goggles – To protect eyes.
- Sodium Thiosulphate
- Hydrochloric Acid
- Distilled water
Diagram:
Method:
- Set up apparatus as shown in the diagram above with the beakers full with concentrations of Hydrochloric acid: 0 molar, 0.2 molar, 0.4 molar, 0.6 molar, 0.8 molar and 1. To do this mix the hydrochloric acid and distilled water using measuring cylinders.
- Use the thermometer to make sure the liquids are the same temperatures.
- Place the beakers on top of the pieces of paper with the black X’s on.
- In 4 of the measuring cylinders measure out 10ml of sodium Thiosulphate.
- Pour one of the measuring cylinders into the beaker and time the seconds taken for the cross at the bottom of the beaker to disappear.
- Record the results then repeat for the other beakers.
- Repeat experiment again 2 more times to get an accurate set of results.
Results:
Conclusion:
The main points to note about the curves are:
- There are no particles with zero energy.
- The curve does not touch the x-axis at the higher end, because there will always be some particles with very high energies.
- The area under the curve is equal to the total number of particles in the system.
- The peak of the curve indicates the most probable energy.
The activation energy for a given reaction can be marked on the distribution curve. Only particles with energy equal or greater than the activation energy can react when a collision occurs.
In this experiment I have found that my prediction was right as the concentration is increased the time taken for the reaction to take place decreases. This means the rate of reaction increases as it takes less time for a reaction to take place, so more take places per second. Using the graphs, with lines of best fit, I can draw a conclusion from my experiment. Firstly I can see the graphs have negative correlation in both cases, meaning that as the concentration increased the time taken for the reaction to take place decreases. Naturally, the above means that the graphs plotting rate against concentration has positive correlation as the concentration is increased so does the rate of reaction. This is because when the temperature is increased the particles will have more energy and thus move faster. Therefore they will collide more often and with more energy. When solutions of reacting particles are made more concentrated there are more particles per unit volume. Collisions between reacting particles are therefore more likely to occur.
Evaluation:
In my opinion the experiment was a very big successful. I obtained a substantial quantity of very accurate results from which I was able to create informative graphs. I obtained a good amount of results. However if I was to repeat the experiment I would also test the effect of temperature on the reaction time.
The range of concentrations was all right but if I were to do the experiment again I would have concentrations of 0.10m, 1.15m, 1.20m, and so on. This would make my results more accurate and it would allow me to make greater assumptions from my results. It was not necessary in testing the 0M concentration because there was no acid in it to react.
To make my results more accurate I could have measured the volumes of liquids more accurately. If I were to repeat the experiment I would have possibly found a more accurate way to measure out the solutions and to determine the molar concentrations. Next time I shall use a burette to ensure that I have an accurate amount of fluid in each test tube.
All my results followed the set pattern, but some were not as close to the line as others. This could have been caused by humans.
Overall I was extremely pleased with my results.
