How does the concentration of HCl affect the rate of reaction with CaCO3?

by tinaye99hotmailcouk (student)

Tinaye Mandishona

Chemistry Investigation – How does concentration affect rate of reaction?

In this experiment we are looking at how concentration affects rate of reaction. We are reacting 0.5 grams of marble (CaCO3) with different concentrations of hydrochloric acid (HCL- 0.25 molar – 1.5 molar). When you react marble (CaCO3) with Hydrochloric acid (HCl) you produce Calcium Chloride (CaCl2), Carbon dioxide (CO2) and water (H2O).

CaCO3(s)+ 2HCl(aq) = CaCl2(aq)+ CO2(g)+ H2O(l)

Variables:

Control variables:

Temperature – temperature can increase the rate of reaction so in our experiment we are going to try keep the temperature the same (will be explained in more detail how it affects rate of reaction in the bottom half of introduction).
Surface area – If we increase the surface area of our reactants we increase the rate of reaction so therefore we will keep the surface area of the reactants the same (will be explained in more detail how it affects rate of reaction in the bottom half of introduction).
Time – We are keeping the time at 1 minute because we used powdered marble so the reaction went very fast because the surface area was very large therefore we decided to make time one of our control variables.
Catalysts – We are not adding any catalyst to our experiment, this is to see how our independent variable has an effect by itself on the rate of reaction.

Dependant variable-

Volume of carbon dioxide produced – we measured the amount of carbon dioxide produced because this was the only product made that we were able to extract with the equipment we were given.

Independent variable-

Concentration – We decided to make our independent variable concentration because we found it more manageable to test and we were not allowed to use catalysts.

Collision theory explains why chemical reactions occur and why they react at different rates. It was proposed by Max Trautz and William Lewis in 1916 and 1918. A reaction can only take place if the reactant particles collide; also the force in which they collide has to be stronger than the bonds of the reactant particles. The activations energy (energy required for a reaction) has to be stronger than the bonds so that they break the bonds and form new one to make new particles (products). Chemical reactions can either be successful or unsuccessful, successful chemical reactions only take place when successful collisions happen; successful collision only happens when the activation energy is stronger than the bonds.

Rate of reaction is how fast/slow a reaction is. There are many factors that can affect the rate of reaction:

Temperature – temperature affects rate of reaction because when you increase the temperature you cause the particles to vibrate causing them to move about more and this increases the chances of the reactant particles colliding also they give the particles more energy lowering the activation energy so the particles can react easier.
Catalyst – Catalyst are substances that speed up chemical reactions without getting used up. Catalysts increase the number of successful collision by creating another way for the chemical reaction to react with lower activation energy. They provide lower activation energy by either breaking the bonds of the reactant materials so that the activation energy decreases or makes them come closer together so they can collide together and react more frequently.
Concentration & Pressure- Concentration increases the rate of reaction because if you increase the concentration you increase the number of reactant particles that could collide in a given area, so there would be more collision occurring. The same thing happens in pressure, you increase the amount of reactant particles in a given space so there are more collisions likely to happen.

Surface area- You can increase surface area by making solids into powders by crushing or grinding them, this allow more of the other reactant particles to react with powdered reactant particles because there would be more area for the other reactant to attack, but if the reactant was a solid the other reactant could only attack the other layer, slowly working its way through it, so by increasing the surface area you increase the rate of reaction!

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You can work out rate of reaction by either doing amount of product produced divide by time or 1000/time to give you the rate of reaction per 1000th.

Preliminary write up

List of apparatus:

0-100 ml Measuring cylinder – we used this to measure how much carbon dioxide was produced.
Burette (replaced the measuring cylinder) – we used this to measure how much carbon dioxide was produced.
Pipette – we used a pipette to put hydrochloric acid into the 10ml measuring cylinder because it helped us put the hydrochloric acid exactly to the 10 ml.
0-10 ml ...

This is a preview of the whole essay

You can work out rate of reaction by either doing amount of product produced divide by time or 1000/time to give you the rate of reaction per 1000th.

Preliminary write up

List of apparatus:

0-100 ml Measuring cylinder – we used this to measure how much carbon dioxide was produced.
Burette (replaced the measuring cylinder) – we used this to measure how much carbon dioxide was produced.
Pipette – we used a pipette to put hydrochloric acid into the 10ml measuring cylinder because it helped us put the hydrochloric acid exactly to the 10 ml.
0-10 ml measuring cylinder – we used this because it eliminated any chances of us putting anything higher than ten ml because the range of the measuring cylinder only went up to 10ml.
Spatula – we used this to put the powdered marble into the weighing boat
Scale – we used this to weigh the powdered marble
Weighing boats – we used this to put the powdered marble into and weigh it on the scale.
Chronicle flask with delivery tube – we used this to put the powdered marble and hydrochloric in, the delivery tube carried the gas produced to the measuring cylinder/burette.
Buckler flask with an attached delivery tube. ( replaced the chronicle flask) - We used this to put the powdered marble and hydrochloric acid in; the delivery tube carried the gas produced to the measuring cylinder/burette.
Bowl – we put water in here to stop the water in the measuring cylinder/ burette from escaping.
Clamp – we used this to keep the measuring cylinder/burette in place
Stop watch – we used this to time the reaction.
Thermometer – used this to measure the solution before and after the experiment because we couldn’t control the temperature.

Method

We started off by washing out the chronicle flask with distilled water (which was later on replaced by a buckler flask with an attached delivery tube)
Weighed out 0.5 grams of marble on a scale. We put a weighing boat on the scale then tarred it; we then used a spatula to put marble powder onto the weighing boat. We made sure that it was 0.5 exact, if there was too much we removed some of the marble powder and if there wasn’t enough we put more powder in until it was 0.5 grams.
We made our concentrations (for 0.25 m we put 7.5 ml of water and 2.5 ml of 1m hydrochloric acid in the 10ml measuring cylinder, for 0.5m we put 5 ml of water and 5ml of 1m hydrochloric acid in the 10ml measuring cylinder, for 0.75m we put 2.5 ml of water and 7.5 ml of 1m hydrochloric acid in the 10ml measuring cylinder, for 1.25m we put 3.75ml of water and 6.25ml of hydrochloric acid into the 10ml measuring cylinder.)
We put 10ml of a certain concentration into the chronicle flask (which was later on replaced by a buckler flask with an attached delivery tube)
We then filled a bowl with water
We also filled the 100ml measuring cylinder (which was then replaced by a burette) with water and turned it upside down and put it into the bowl of water.
We used a clamp to keep the measuring cylinder (which was then replaced by a burette) in place.
We put the delivery tube into the measuring cylinder when it was in the water bowl.
We then put the powdered marble into the chronicle flask (which was later on replaced by a buckler flask with an attached delivery tube) and put a bung on top of it. We removed the bung when the experiment had been going for 1 minute. We noted down how much carbon dioxide was produced and washed out our flask with distilled water after the experiment to get rid of contaminates.

We changed quite a lot of things in our experiment. We started off trying to test how concentration and surface area affect rate of reaction; we used 2 grams of large marble chips and small marble chips. We also used 20 ml of Hydrochloric acid as well. We figured out trying to test surface area and concentration together was hard because when we put 2 grams of large marble chips in our lowest concentration of hydrochloric acid, nothing was produced so we just ended up testing how concentration affects rate of reaction.

We were using 2 grams of small marble chips and 20ml of hydrochloric acid, this reacted to fast and too much gas was produced, it was too much for the measuring cylinder to contain so we ended up using 1 gram of small marble chips. We also changed the amount of hydrochloric acid to 10ml; we noticed that this produced the same results when we were using 20ml of hydrochloric acid. We ended up using 0.5 grams of marble chips because at 2m of hydrochloric acid (highest concentration) while using 1 gram of small marble chips, there was a vast amount of gas produced and the measuring cylinder couldn’t hold all of it.

We noticed by using the small marble chips we weren’t keeping the surface area constant so we ended up using 0.5 grams of powdered marble so that the surface area was constant, this gave us more consistent results because our results were all over the place when we were using the small marble chips. We started off using a chronicle flask with a delivery tube attached to the bung, but we ended up using a buckler flask with a delivery tube attached because it was more reliable in terms of collecting gas.

We used a burette instead of a measuring cylinder because it had a better range than a measuring cylinder so we could see how much gas we collect to 1 decimal point e.g. 49.2.

We were not washing out our apparatus at first but then we started to wash them out so we could get rid of any kind of contaminates in the apparatus. We used tap water at first but then we used distilled water because distilled water is pure water, only containing H2O so eliminating any chances of contaminates unlike tap water which contains minerals such as phosphorous etc which could affect our experiment.

We noted down the temperature for the reactants before and after the experiment because we couldn’t keep the temperature constant.

We only had one anomalous results which was 29.10, this could have occurred from either using more than 0.5 grams of powdered marble or not washing out the buckler flask properly, leaving contaminates to react with the hydrochloric acid, using tap water instead of distilled water to wash out the apparatus or we could have used the wrong concentration in the experiment.

The graph shows us that as you increase the concentration, there is more hydrogen being made. The r² value also tells us that our results are very accurate because the r² value is close to 1 (0.9744). The R² value tells us how our results fit the line of best fit, if the r² is one, then our results fit the line of best The R² value tells us how our results fit the line of best fit, if the r² is one, then our results fit the line of best fit perfectly, making our results very accurate good making our results very accurate.

This graph shows us that the rate of reaction increases as the concentration increase. The r² value is close to one (0.9744) therefore our results are quite accurate. The R² value tells us how our results fit the line of best fit, if the r² is one, then our results fit the line of best fit perfectly, making our results very accurate.

Method

List of apparatus:

Stop watch
Bowl
Pipette
0-10ml measuring cylinder
Burette
Buckler flask with an attached delivery tube
Weighing boats
Spatula
Scale
Clamp
Thermometer

Method

We started off by washing out our buckler flask with an attached delivery tube with distilled water
Weighed out 0.5 grams of marble on a scale. We put a weighing boat on the scale then tarred it; we then used a spatula to put marble powder onto the white dish. We made sure that it was 0.5 exact, if there was too much we removed some of the marble powder and if there wasn’t enough we put more powder in until it was 0.5 grams.
We made our concentrations (for 0.5m we put 5 ml of distilled water and 5ml of 1m hydrochloric acid in the 10ml measuring cylinder, for 0.75m we put 2.5 ml of distilled water and 7.5 ml of 1m hydrochloric acid in the 10ml measuring cylinder, for 1.25m we put 3.75ml of distilled water and 6.25ml of hydrochloric acid into the 10ml measuring cylinder, for 1.5m we put 2.5ml of distilled water into 7.5ml of 2m hydrochloric acid into the 10 ml measuring cylinder.)
We put 10ml of a certain concentration into the buckler flask with an attached delivery tube
We then filled a bowl with water
We also filled the burette with water and turned it upside down and put it into the bowl of water.
We used a clamp to keep the burette in place while we did other things.
We put the delivery tube into the burette when it was in the water bowl.
We noted down the temperature of the hydrochloric acid in the buckler flask before the reaction.
We then put the powdered marble into the buckler flask with an attached delivery tube and put a bung on top of it.
We took the temperature of the solution left in the buckler flask after the experiment.

We removed the bung when the experiment had been going for 1 minute. We noted down how much carbon dioxide was produced and washed out our buckler flask with distilled water after the experiment to get rid of contaminates. We noted down the temperature for the reactants because we couldn’t keep the temperature constant.

Results

I got four anomalous results, three of them were very far from the averages and one of them wasn’t really very far from the average (I didn’t include the anomalies in the calculation of the averages) but it wasn’t close enough to the other range of data so I made it an anomaly so that I could repeat the test again and get a better spread of data. The anomalies could have occurred from either using more than 0.5 grams of powdered marble or not washing out the buckler flask properly, leaving contaminates to react with the hydrochloric acid, using tap water instead of distilled water to wash out the apparatus or we could have used the wrong concentration in the experiment.

This graph shows that there is an increase of carbon dioxide produced when you increase the concentration. The R² value is better than our preliminary R² value and really close to one (0.9889) meaning our results are really close to the line of best fit therefore our results are quite accurate because R² value was created to show us how close the results fit the line of best fit by displayed a number from 0-1, 1 meaning that all the results fit the line of best fit and 0 meaning none of the results fit the line of best fit.

The rate of reaction increases as the concentration increase. The R² value is better than our preliminary R² value and really close to one (0.9889) meaning our results are really close to the line of best fit therefore our results are quite accurate because R² value was created to show us how close the results fit the line of best fit by displayed a number from 0-1, 1 meaning that all the results fit the line of best fit and 0 meaning none of the results fit the line of best fit.

Conclusion

Overall my results show that concentration increases the rate of reaction. Concentration increase the rate of reaction because if you increase the concentration of a substance you put more and more of it in a defined space therefore having a lot of reactant molecules in a defined space creating more chances of collisions between two reactants, for example as we increased the concentration of hydrochloric acid, we increased the number of hydrochloric molecules in the buckler flask, allowing more collisions with the marble molecules, therefore creating more products at a quicker rate each time!

Evaluation

My experiment went very well, we got some consistent results and our method was quite reliable and accurate. Even though we got some good results, we did have a lot of limitations such as:

We couldn’t control the temperature of the apparatus because we didn’t have facilities that were temperature controlled, so the temperature wasn’t kept constant. Even though we couldn’t keep the temperature constant, we noted down the temperature of the solution before and after the experiment.
The range on some of the apparatus wasn’t very good, we could only see how much carbon dioxide was produced to the nearest 10th of 1 cm³ on a burette
Due to us trying to keep the surface area constant, we used powdered marble, and because by making marble a powder, the surface area was very great causing a quicker reaction leading on to majority of the carbon dioxide being caught at around 30 seconds or less during the experiment; and little bubbles were let off at a 5 second interval after 30 seconds. The time when the majority of the bubbles were captured always decreased making the reaction faster each time we increased the concentration.

If I could make any improvements to my method and apparatus, I would try and make the range of the Burette better so I could have less chance of making an error when measuring how much carbon dioxide was produced, also I would try to get little particles of marble with the same surface area so that I don’t have the majority of the reaction taking place within the first 10-20 seconds or get lower concentrations. I would also try doing my experiments in a heat controlled room so that the temperature can be kept constant during the day when I do my experiment so my results could be considered reliable.

Results:

For my preliminaries I only got 1 anomaly but I feel I didn’t check the ranges very well because there are parts were the results are 0.4-0.5 cm³ gap in-between which isn’t very good. For my main results I checked if the ranges were very close and they were, I repeated one results to just get a better range because it was 0.3 cm³ apart from the other results.

As you go from one concentration to another you can see that there is a change in terms of how much carbon dioxide is produced. The average amount of carbon dioxide produced goes up by approximately 3-4 cm³ as you move up from 0.25-1.5 molar.

My spread of data for my preliminary work is very bad because the results were too far apart from each other having an effect on the averages so my results wouldn’t be considered very accurate and reliable, if you look at my preliminary graphs my first two points of data are far off the line of best fit unlike the other points which nearly fit the line of best fit .But my main result’s spread of data is very good, with me repeating one of my results just to get a better spread of data with the majority of my results fitting the line of best fit.

I feel my results are quite reliable because I repeated my experiment when I got anomalous results, I repeated my experiment three times also I got a good spread of results for my main results, but my results could be considered unreliable and inaccurate due to no care taken on my preliminaries because I didn’t make sure the range of my results was very good and my average result for 0.25 m is nearly 10cm³ less than my average results for 0.50m, meaning something wrong happened because all the other results are 3-4 cm³ apart.

Conclusion:

I can make the right conclusion for my results because the range of results and spread of data for my main results are quite good, my results are also quite reliable because I repeated them 3 times and even repeated my experiment when I got anomalies, the fact I got anomalies ruins the chances of my results being very good because by getting anomalies my method has flaws in it.

There thing preventing me from getting a totally good conclusion are the anomalies because some of them are out of the range of the data and also I didn’t take my preliminaries as serious as my main results resulting in an odd string of results for 0.25 molar which doesn’t fit the pattern of my other results.

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