Marble chips Dissolved in varied concentrations of HCl.

Marble chips Dissolved in varied concentrations of HCl

Planning

Before the apparatus was set up the experiment had to planned as fairly as possible. This involved only changing one variable at a time, therefore all the other variables had to be kept constant. Firstly the mass of the chips was kept as similar as possible, I did this by weighing the chips to be at an approximate mass of 5.0g on a top pan balance. From a previous experiment I did involving different sized marble chips I found that the surface area greatly effects the rate of reaction, therefore the marble chips were separated by hand using a sieve to obtain pieces of medium size. Another variable I took into account was the volume of HCl will use, I chose to use exactly 20cm for each experiment. Also I intend to measure the initial temperature of the acid before the experiment with a thermometer.

After deciding how to approach all of the variables in the experiment I decided how to carry out my experiment. I decided to use different concentrations of HCl in 0.5M, 1.0M, 1.5M and 2.0M (1mole/dm ). To obtain these different concentrations I used a solution of 1.0M which was already prepared and the same with a 2.0M solution. However in order to create a 0.5M and 1.5M solution I had to mix different solutions. The 0.5M solution was made using 10cm of deionised water and 10cm of 1.0M solution, this was then stirred with a glass rod. To make 1.5M solution the same concept was used, I mixed 10cm of 2.0M solution with 10cm of 1.0M solution.

I then measured and recorded how much volume of gas (cm ) was given off each 10sec using a stopwatch. Finally the gas syringe is an excellent piece of apparatus as it is very accurate, however I will have to make sure that the clamp does not hold on to it too tightly as this could effect the results.

To help obtain the best possible results I will repeat each experiment twice and then find an average set of data.

I predict that the high molarity concentration solution will have a much faster rate of reaction than the weaker solution. ...

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To help obtain the best possible results I will repeat each experiment twice and then find an average set of data.

I predict that the high molarity concentration solution will have a much faster rate of reaction than the weaker solution. I have predicted this from my knowledge of a previous experiment and scientific knowledge. Recently I did a similar experiment involving magnesium instead of the calcium carbonate, from this I found that the higher concentration solutions, faster the reaction, therefore I believe the same results may occur. I think that this happened because the more HCl in the solution the greater the concentration and there will be more particles colliding and more energy and therefore a faster rate of reaction. The reason I think that the rate of reaction will increase is that the experiment is exothermic, this means that it will give itself more energy and therefore more collisions and faster collisions. Also in the 2.0M solution compared with the 0.5M solution there are much more HCl particles in the same volume so the are going to collide with each other more often (see below)

Therefore I predict that the rate of reaction will increase with the concentration of the HCl solutions.

Evaluating Evidence

I think that the experiment went very well. This is because I got all the results that I wanted and they look very good. The results were very accurate and so I am able to make a good conclusion. From looking at my results I can see that there were no poor results which was a good thing and it proves that everything went very well. Even though the experiments went very well I decided to repeat one concentration of acid twice just to see if I could repeat the experiment and get roughly the same results, which is what I did do, and these to went very well. There was no real source of error in the apparatus along as it all was working well and the way it should of been. The only possibility was if the temperature of the acid had changed from when we did the first reading to the finish i.e from when we did the first experiment, the acid hopefully would have been the same temperature.

Analysing Evidence and Conclusions

From looking at my results and graph I am able to conclude that the more concentrated the acid the quicker the reaction happened and the more gas was produced. As we look at the graph we can clearly see that in all five results at the beginning the reaction happened more quickly than at the end where we can see that it started to tail off.

Before I did the experiments I made some predictions they were that the more concentrated the acid was the quicker the reaction would happen and more hydrogen would be produced. This was completely correct because what I thought would happen did.

At this point we are able to answer our main hypothesis which was 'how does changing the concentration of acid affect the rate of reaction between hydrochloric acid and calcium carbonate.' The answer to this would be that changing the concentration of the acid will either make it go slower or quicker and more or less gas would be produced depending on whether the concentrations were more or less.

Overall this was a very successful experiment and everything went very smoothly, and that was why my results were very good, and I am able to make a conclusion like this.