2.Volume of liquid: I will keep the amount of liquid at 50 ml, because if I don’t keep the amount of liquid constant I will change the amount of acid in contact with the marble chips, because if there is more HCL in contact with the marble chips than according to collision theory there will be more particles of HCL with sufficient energy available for collision. 3.Amount of air in gas collection chamber prior to experiment: I will check that there is no air in the collection chamber, because although this may disrupt my results that much, but if the collection camber is slightly tilted it could affect my results quite a bit.
4. The point at which I plan to start the clock: I have decided to start the clock from the time which I put the bung on the conical flask due to the fact that it is the only way to maintain a constant, and suitable starting point because for each experiment all the marble chips will not hit the acid at the same time so it is inappropriate to start timing from the moment the marble chips touch the acid. So b timing it from the time I put the bung on I make sure when I start timing all the marble chips are in contact with the HCL.
5.Temprature of liquid: I will keep all my HCL and water at room temperature. I will want to control this fact because according to collision theory at higher temperatures particles have more kinetic energy. This means that they are moving quicker and will collide more often. They will also have more energy when they collide, meaning that the higher temperature increases the number of effective collisions in which the particles collide with enough energy for a reaction to occur.
6.Weight of marble chips: I will keep the weight of the amount of marble chips I use the same, to keep the amount of reactant the same. If I alter the weight I will change the amount of marble chips in contact with the HCl, and according to collision theory the fewer amount of particles of solid reactant available to react there is, it is less likely that collisions will occur with enough energy.
7. Concentration of acid: I will alter the amount of concentration of acid because this is the variable that I am investigating. To vary the concentration I will keep the amount of liquid the same but I will add water and take away acid to vary the concentration. For example to get a concentration of 80% will use 40ml of acid and 10 ml of water. Concentration is a variable because according to collision theory more concentrated solutions contain more particles in the same space, making them more likely to collide. The increase in the number of collisions with sufficient energy increases the rate of reaction.
2. What I predict will be the effect of varying the key factor.
I predict by increasing the concentration of acid I will increase the rate of reaction.
The reasoning behind my prediction is one based on collision theory. I predict that because more concentrated solutions contain more particles in the same space, making them more likely to collide, which will increase the number of collisions with enough energy.
I predict that because increasing the concentration increases the amount of collisions. So based on that theory if I double the amount concentration then the rate of reaction should also double. I predict that based on my preliminary work at 60 seconds the amount of gas given of at a concentration of 80% should be approximately 50 cm3 and at the concentration of 40% the amount of gas given of should b approximately 25 cm3.
I also predict that because it is an exothermic reaction it will speed up as it goes on. I have based this prediction on collision theory as well because at higher temperatures faster moving particles have more kinetic energy. This means that they are moving quicker and will collide more often. This means that they will have more energy when they collide.
3. Apparatus
Conical Flask
Bung with vent tube attached
Stand with a Clamp
Small measuring cylinder
Water bath
Gas collection chamber
Thermometer
Weighing scale
Stopwatch
Calcium carbonate marble chips
Hydrochloric acid
Water
Paper
Safety glasses
Lab coat
4.Safety
Safety always comes first so here are some key facts:
- Always wear safety goggles because we are dealing with acid which could possibly splash into your eyes
- Always wear lab coats to avoid damage o clothes and skin
- Always pay attention to what you are doing because it is very easy to drop something, or walk into somebody carrying dangerous substances
- Never run in the lab as you run into someone or trip up and injure yourself.
3. Method
- First I will fill up the water bath to ¾ full. Then I set up the boss and clamp which will be used to hold the gas collection chamber upside down. I will then fill up the gas collection chamber, turn it upside down, and put it in the water bath and attached it to the boss and clamp leaving enough room for the vent tube.
- Then you will need to weigh out the marble chips to 5 grams, but first put a piece of paper on the weighing scale and press ‘re-zero’ in order to keep the scale in good condition.
- Then you will need to measure out the liquids so first get out a conical flask, and a small measuring cylinder. Then measure out the acids. The mount of acid will change, as the concentration increases. For 80 % concentration use 40 ml of HCl, for 70% acid use 35 ml of HCl, for 60 % acid use 30 ml of HCl, for 50 % acid use 25 ml of HCl, and finally for 40 % acid use 20 ml of HCl. Once you have measured out how much acid you are going to use pour it into a conical flask. Then you will need to measure out how much water you are going to use. To find this out subtract the amount of acid you are using by 50. Once you have worked this out measure it out using a measuring cylinder, and pour this also into the conical flask. Finally check that all the liquid you have placed in the conical flask adds up to 50ml
- Then get out a bung with a vent tube, and check it fits your conical flask. Once you have checked this ask someone to assist you in timing your experiment. Then check that you conical flask and vent tube are in the right position to start timing.
- Once you are ready to take down the readings put your marble chips in the conical flask, and put the bung with the vent tub firmly in place. As soon you put the bung on the conical flask get the person who is assisting you in timing to start the clock.
- At 15 second intervals note down the amount of gas given off. To do this simply locate the level at which the water is and measure how low the water is.
- After 120 seconds or when all the water in the gas collection chamber runs out, the experiment is finished.
- When clearing up first take the bung out of the conical flask and pour it into the basin provided, then rinse the conical flask well, and check there is no liquid so that it is ready for the next experiment. Then take out the gas collection tube, and put it to one side. Finally check that the water basin is not overflowing, and hat there is enough space for the next experiment.
6. Conclusion
I have made sure my planning is simple, and my experiment is a safe one by doing preliminary work. I have also checked the range of my readings, and decided to use what I believe to be a suitable range based on my preliminary work. In order to make sure my results are as precise as possible I will take more than one reading.
