- Surface area
- Concentration
- Catalyst
- Stirring
I will be looking at the above in more detail:
Temperature When the temperature of a reaction is increased, heat is supplied to the particles involved in the reaction, and since heat is a form of energy we should expect that energy to go at least partly to increase the speed at which the particles travel. Therefore higher the temperature the faster the particles travel, causing more collisions, so the rate of reaction would be increased. If the temperature is kept low, the particles won’t have as much energy and there would be less collisions resulting in a slower rate of reaction.
Concentration- the more concentrated a solution ( are the higher the pressure of gas) the faster a reaction occurs. This is because there are more particles in a given volume to react. For example;
As you can see in diagram (B), the concentration of hydrochloric acid is higher therefore meaning a greater number of particles acting on the calcium carbonate (marble chips), this allows it to have more collisions resulting in a higher rate of reaction.
Catalyst- A catalyst speeds up a chemical reaction by lowering the activation energy therefore making it easier for a reaction to occur. The catalyst remains chemically unchanged at the end of the reaction.
Volume of acid- The amount of acid that you add- If more acid is added, more the number of acid particles therefore faster the reaction.
Stirring- the more we stir, the temperature rises giving the particles more energy and therefore a higher rate of collisions, resulting in a faster rate of reaction.
Prediction-I predict that the rate of reaction will increase as the concentration of Hydrochloric acid increases.
Equipment
- Stop watch
- Gas syringe
- 3 molar acid
- measuring cylinder
- distilled water
- conical flask
- delivery tube
- marble chips
- goggles
- thermometer
- retort stand
Diagram
Apparatus for measuring the rate of reaction between calcium carbonate and dilute hydrochloric acid.
Method The experiment is set up as shown in the diagram. 50ml of acid are carefully measured and placed in the flask. The marble chip is rested in the neck of the flask and the bung and tube are inserted. The flask is turned upright at the same time the stop watch is started. The time taken to collect 40mlof carbon dioxide is measured and this volume is used as a measure of the rate of reaction.
This procedure is repeated several times using different concentration of acid, using 40ml acid+10ml water; 30ml acid+20ml water; 20ml acid+30ml water and so on.
Fair Test--Care must be taken to keep any other factors constant:
For example:
- The mass and surface area of the marble chips must be the same for each reading.
- The total volume of acid must be 50ml in each case.
- The temperature of the acid must be kept constant.
Safety –I will also take some safety precautions:
- Wear safety goggles-to prevent hazard material to come in contact the eye
- Lab counts- to prevent hazard material spilling onto me
- Tie hair(for people with long hair)-to prevent heair getting in the way of the experiment.
Results table
Conclusion- My results proved my hypothesis. The higher the concentration of acid the faster the rate of reaction. The results also show that the background research that I did showed a valid pattern, as the concentration doubled so does the rate of reaction. Between 0.5 and 1.0 moles the amount of time roughly halves as the concentration is doubled, this is also true between 1.0 and 2.0 mol gap. If my results had been more accurate I think the results would show the concentration of the acid and the rate of reaction to be proportional.
The graph also supports my prediction. On the graph the steeper the curve, the faster the rate of reaction. Also from the graph I was able to work out the average rate of reaction for the gas produced.
Evaluation- overall I am pleased with my result and the way the experiment was conducted. I think the results were fairly accurate and proved my hypothesis. To make the results more accurate I would consider repeating the experiment more times and then taking an average From the next I would conduct a preliminary experiment to find out which condition are best suited for the following experiments (for example- To find out which temperature will be best suited, I could experiment with a range of temperatures; I could also do this with the concentrations and the mass of the calcium carbonate. The experiment should not take to long to conduct as we are limited for time, but at the same time should give us enough points to plot on the graph.
I had only one anomalous result, this could be due to me miss reading the amount of gas given off. I could have made my results more accurate by sieving the marble chips( calcium carbonate) this would help make the chips similar sizes, therefore the surface area of the chips would stay the same. I could have also check the temperature every minute to see if it was constant.
The other thing that I would like to investigate would be the experiment of time against amount of gas produced to show at which points the rate of reaction was at best curve/line of reaction. I would like to also investigate other factors, which affect the rate of a reaction like temperature and the volume of the hydrochloric acid and see how they would affect the rate of reaction.
- For the evaluation you have to include all this
- What difficulty you had with the experiment
- Look at odd results and justify it
- Suggestion for improvements
