There are two possibilities for increasing the rate of reaction:
- The activation energy is reduced so there is a better chance of particles having enough energy to react.
- The number and the strength of the collisions are increased so that the reaction can happen faster. If the particles have more energy then more particles will be able to react.
In a concentrated acid solution there are more acid particles as the concentration is increased compared to the number of marble chip particles so more collisions will take place.
Planning + Fair Test
Before the apparatus are set up the experiment must be planned as fairly as possible. To do this I must only change one variable at a time, therefore I will keep all the other variables the same. The mass of marble chips should be kept the same or as similar ass possible. I will do this by weighing the chips to be at an approximate mass of 2g on a top pan balance. Another variable I will keep the same is the amount of HCl I will be using. I will try to use exactly 50 cm for each experiment. Also I will intend to measure temperature of acid so that it is roughly the same every time, I will use a thermometer to do this.
I have decided to use different concentrations of acid for my experiment I will be testing 0.25M, 0.5M, 1.0M, 2.0M and 3.0M (1 mole/dm). To obtain the 0.25 concentration I will mix the 0.5m concentrations with half part water and stir it with a glass rod.
I am going to record the amount of gas (cm) given off every 30 seconds using a stopwatch. I will use a gas syringe to do this as it is a very accurate piece of equipment, however I will make sure that the clamp is not too tight has this may effect my results.
To obtain the best results I will do each experiment twice and then I will work out the average of the two. I will do this by:
Set of results 1 + set of results 2
2
There are three other experiments I could do to look at rates of reaction:
- Temperature
- Catalysts
- Surface Area
Temperature: You can use different temperatures of HCl. The prediction for this is the higher the temperature the quicker the rate of reaction. This is because the particles have more energy, so they will move faster. This will result in the particles colliding move frequently and increasing the speed of the reaction.
Catalysts: They will reduce the activation energy so in return this will make more successful collision. The reaction will be faster by the catalysts will not be used up during the reaction. Then the activation energy is lower not my energy is needed to make the reaction successful.
Surface Area: Solid reactants like marble chips are affected by surface area.
The larger the surface area, the more collisions will take place. This will increase the rate of reaction and decrease the time taken.
Safety:
For safety I will where safety goggles and I will try not to spill any of the acid. I will also push my chair and bag under the table. I will also check that the equipment is safe to use.
Apparatus
- Hydrochloric acid
- Water
- Calcium carbonate chips
- Conical flask
- Glass capillary
- Syringe
- Rubber bung
- Spatula
- Stand
- Clamp
- Measuring cylinder
- Stopwatch
- Top pan balance (measure marble chips)
Method
Once the aperatus has been set up as shown above, 50 cm³ of the HCl acid solution will be mearsure using a mearsuring cylinder. This will be poured in to a conicle flask. I will then mearsure out 2g of CaCO chips using a top pan balance. This will be put in to the conicle flask and the rubber bung with the syringe attached willo be put over it immediately afterwards. I will then start the stop clock.
I will check my experiment every 30 seconds I will record how much gas is produced and record it. I will do this up untill 90 seconds I will repeat this for each consentration. My results will be recorded in a table and then I will write them up after.
This experiment will be repeated and carried out in the same way I will only change the consentration of the acid. I will not change the amouunt of solution used.
Results Table (set of results 1+2)
0.25 consentration
0.5 consentration
1.0 consentration
2.0 consentration
3.0 consentration
Conclusion + Evaluation
From looking at my results I am able to conclude that the more the concentrated the acid is the quicker the rate of reaction is. I belive that some of my results are not very reliable as there is a big difference between the two times that I repeated the experiment . I feel I have made them a bit more accurate when I averaged them. I think I got these odd results beacause the second time I did the experiment the clamp might have been a bit tigher than the first time. I could improve my method by doing step by step pictures and add more detail.
I feel my method was very accurate as some of my results show I feel I someelse who had not done the eperiment before could easily do it by using my method. I didn’t have mush trouble reading the gas syringe I just made sure that the clamp wasn’t in the way of the mearsurments printed on there.
If I where to do this experiment again I will use a different consentrations of HCl and also a different amount of CaCO.
The change in acid will make the reaction eithere slower or faster and more of less gass will be produced this depends on if the consentations where higher or lower.
This is also because of the collision theory. The collisions between reactant particles are needed for the reaction to take place in order to form a product. Some collisions are successful and give a product but others are not this is because some of the particles don’t have enough activation energy.
Activation energy is the amount of energy needed for the reaction to be started. If there is enough energy the reaction takes place and a produced is formed, if the amount is not right no reaction will take place.
There are two possibilities for increasing the rate of reaction:
- The activation energy is reduced so there is a better chance of particles having enough energy to react.
- The number and the strength of the collisions are increased so that the reaction can happen faster. If the particles have more energy then more particles will be able to react.
The evidance I have collected supports my conclusion.
The different consentrations also relfects my conclusion
There are three other experiments I could do to look at rates of reaction:
- Temperature
- Catalysts
- Surface Area
Temperature: You can use different temperatures of HCl. The prediction for this is the higher the temperature the quicker the rate of reaction. This is because the particles have more energy, so they will move faster. This will result in the particles colliding move frequently and increasing the speed of the reaction.
Catalysts: They will reduce the activation energy so in return this will make more successful collision. The reaction will be faster by the catalysts will not be used up during the reaction. Then the activation energy is lower not my energy is needed to make the reaction successful.
Surface Area: Solid reactants like marble chips are affected by surface area.
The larger the surface area, the more collisions will take place. This will increase the rate of reaction and decrease the time taken.
My prediction was accurate. As I said, the higher the concentration, the faster the reaction. I think that my prediction and my results match perfectly. In conclusion, I think that the experiments worked well in some places, and worst in others.
The 0.25 molar is very weak and has little gas given off. This is also the same for the 0.5 and 1 molars. The 2 and 3 molar are very strong and give of a lot more gas. This backs up my prediction and my conclusion that the stronger the concentration the more gas is given off and the quicker the rate of reaction.
Rates Of Reaction Graph
