HCL Vs Calcium Carbonate Essay, Research Paper

Scientific Knowledge

There are many different factors that can effect the rate of a reaction, some of these are as follows:

Temperature- The higher the temperature the more energy each particle will have which means it will vibrate more, causing the amount of collisions to increase. If the particles collide more, the rate of reaction is increased.

Concentration of Acid- The higher the concentration of acid, the more particals there are to react with. If for example the concentration of Hydrochloric acid is doubled then there are more Hydrochloric particles present and so there will be more chance of the particles colliding.

Particle Size (surface area)- If one of the reactants is a solid then it can be broken down into smaller pieces or into a powder. This gives the reactant a larger surface area, meaning there is a larger surface to work on and so there is more chance of particles colliding.

Activation Energy Needed- Reactions only happen if the particles collide with enough energy. At a higher temperature there will be more particles colliding with enough energy to make the reaction happen. This initial energy is known as the activation energy.

Catalyst- A catalyst will reduce the activation energy and makes more successful collisions. When the activation rate is lower not much energy is needed to make the reaction successful.

Prediction

My prediction is that if the concentration of the acid increases there will be an increase in the rate of reaction for example the highest concentration will have the fastest reaction time.

I carried out a preliminary experiment to help me in my prediction. I prepared marble chips and concentrated acid and did a small experiment, the results were clear and in a few seconds it was almost finished. When we used very dilute acid it took so long for it to react and the amount of gas given off was much less..

If the concentration of an acid increases, the rate of reaction will also increase. When the acid has a high concentration there are more particles available to react with each other, therefore the amount of collisions will be greater.

Fair Test

So that I can say that my results were reasonably accurate and reliable, I must conduct a fair test. I am changing the concentration of Hydrochloric acid in my experiment so all other variables must be kept the same, if they are not then they may interfere with my experiment. Certain factors will be difficult to keep the same such as the temperature but as long as the experiment is carried out quickly and during one session I do not think it will effect my results to the point of them being anomalous.

Apparatus

Gas Syringe- To collect the Carbon Dioxide

Marble Chips- I will be using small chips of Calcium Carbonate. Reactant

Hydrochloric Acid- Reactant

Conical Flask- Cone shaped flask with a rubber stopper in place to hold the reactants.

Clamp + Stand- To hold the Conical flask and Gas Syringe in place

Stop Watch- To time the experiment

Scales- To accurately weigh the Calcium Carbonate chips

Method

Set up the apparatus as in the above diagram. I used the same procedure throughout the experiment. I measured Hydrochloric acid and water in the following quantities:

10ml Water

7.5ml Water : 2.5ml Acid

5ml Water : 5ml Acid

2.5ml Water : 7.5ml Acid

10ml Acid

Once I measured the correct concentration of acid I selected my marble chips. I selected 4 marble chips that were roughly the same shape and size as each other, as I was measuring how fast the reaction takes place, changing the surface area of the marble chips would alter the speed of the reaction and would interfere with my investigation. The four chosen marble chips were placed on a set of sensitive scales, this weight was used throughout the experiment and the four marble chips had to be the same weight. The stop watch was then readied and the Marble chips were placed inside of the conical flask, as soon as the HCl and Marble chips were placed together, the rubber stopper was put in place,this was done as soon as possible as any gas escaping can give me anomalous results. The amount of gas was measured at 15 second intervals and the results were logged. I took the results until the Calcium Carbonate had completely dissolved and the reaction had stopped. To make my results more reliable I repeated the experiment 3 times, this would hopefully account for any anomalous results and would support my prediction without doubt.

Evaluation

The experiment went very well. There were no anomalous results and nothing went wrong. Although I have some ideas which may gain a more accurate reading. Firstly, the surface area of the marble chips were not perfect. It could have been made better if I had used powdered marble chips because the surface area of each wieght of powder would have been a lot similar. If I did use Powder however, the concentration of acid may have had to be weakened as the reaction would have taken place a lot quicker due to the very large surface area and readings wouldn’t have been as accurate. Secondly, an inaccuracy may have been caused by the fact that the temperature may have dropped during the reaction. This could have been used if I used a water bath to heat up the acid to a constant temperature. You have to allow for a margin of human error during the experiment, some people react slower than others and you have to rely on the person taking the readings with the stopwatch.

Conclusion

I conclude from my results that acid concentration does effect the rate of reaction. My graph clearly shows that as the concentration of the acid was increased the reaction took place in less time. There is a significant difference between the amount of time taken from the lowest concentration to the highest concentration of acid. The graph is not linear and there is a slight curve in the results, this shows that the rate was not proportional and the rate of the reaction changed. This may be because of a change of temperature in the room during the experiment. It also may be because the reaction was not instantaneous and it took a second or two for the reaction to speed up, this is described as an exponential rate.