In the preliminary experiment I will investigate the suitable conditions for this experiment – the volume of hydrochloric acid to use and the surface area of marble chips.
For this experiment I predict that the higher the concentration of hydrochloric acid, the faster the rate of reaction will be. I predict that the reaction will occur as shown below:
Calcium + hydrochloric calcium + water + carbon
Carbonate acid chloride dioxide.
CaCo3 + 2HCL CaCl2 + H2 O + CO
Reactant Product
I think that the rate of reaction is affected by the concentration of the hydrochloric acid because the rate of reaction depends on how frequently the reactant particles of the reacting substances collide. A more concentrated substance has more reactant particles in a given volume than a more dilute substance. As there are more particles, the frequency of successful collisions is greater, and the reactions happen faster.
When a reaction takes place, the particles of the reacting substance must collide with each other. A fixed amount of energy, known as the activation energy, must be reached for new products to be made, and the old bonds need to be broken. If the particles collide fast enough and in the right direction, sufficient energy to break these bonds will be produced (the activation energy), which will allow the reaction to take place. However, if this energy is not produced, a reaction will not take place, so not all collisions result in a reaction. The reaction can be speeded up if the number of collisions increases.
I predict that the rate of reaction will increase when the hydrochloric acid is most concentrated. To change the concentration of a solution, we dilute it by adding water.
The predicted reaction additionally tells us that although the calcium carbonate or marble is soluble in water, the gas that is produced from this reaction (carbon dioxide) is not as it displaces the water.
The preliminary work was done for me to decide reasonable values for the volume of hydrochloric acid used and the size of the marble chips, i.e. the variables. For both variables I recorded the time it took for 50cm3 of carbon dioxide gas to be produced. The concentration of acid remained the same throughout the preliminary experiment because it was the values for the constants that we are finding out.
Aim
To investigate the size of the chips and the volume of hydrochloric acid used, so that in the main experiment I have little difficulty and reasonable values.
Prediction
I predict that the size of the chip used will be medium because this will give an in – between value for the time taken and therefore the time taken to give off 50cm3 will not be too short but will not take too long. Additionally I predict that the volume of hydrochloric acid used in the main experiment will be 20 or 25cm3 because similarly it will give a time not too long but not too quick.
Safety
- Wear safety goggles to protect my eyes from any harmful chemicals.
- Taking care when handling chemicals, particularly Hydrochloric acid because it is an irritant.
- I will not touch my eyes or mouth until I have washed my hands thoroughly with soap after conducting the experiment.
- Taking care when using glassware to prevent injury.
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4 mol/dm3 is the most concentrated solution I will use. This is because a solution with a higher concentration will produce a lot of acidic fumes.
Apparatus
- Measuring cylinder - To measure the volume of the acid.
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Stopwatch – To measure how long it takes for 50 cm3 of carbon dioxide to be given out.
- Safety goggles – To insure that in the case of accidents products do not reach my eyes, because hydrochloric acid in particular is dangerous to the eyes.
- Calcium carbonate; marble chips of different sizes – so that the constant (the size of the chip) can be decided.
- Hydrochloric acid – To react with the calcium carbonate.
- Bung – To allow the carbon dioxide gas to pass along to the gas burette.
- Conical flask – Where the reaction between the marble chips and hydrochloric acid will take place.
- Trough – Enables carbon dioxide gas not to escape so that it can be measured.
- Clamp – To securely hold the gas burette.
- Gas burette – To contain the carbon dioxide gas so that it can be measured.
Method
- We filled up the trough and gas burette with water to the top.
- Then we filled the conical flask with hydrochloric acid of the range: 20, 25 and 30 cm cubed.
- Following this the gas burette was placed on a clamp and was placed facing downwards so that the open end was inside and surrounded by water.
- We then placed the delivery tube in a position where it was directly beneath the gas burette and also was going through the bung.
- The different sizes of chips were then weighed so that the different sizes of chips could add up to 1 gram. We found that equivalent to 1g was 1 large chip, 3 medium chips and 6 small chips. Furthermore the chips were dropped in the conical flask and the bung was immediately placed on the flask while the stopwatch was started.
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After that we recorded the time taken for 50cm3 of carbon dioxide given out by stopping the timer when the burette had been filled up with carbon dioxide and therefore 50 cm3 of water had been pushed out.
Results
Size Of Chip
N.B. The chips were all equivalent to the mass of 1 g and 20 cm3 was the amount used in the preliminary experiment – a value gained from the preliminary prediction.
Volume Of Hydrochloric Acid
N.B 3 Medium chips, equivalent to 1g, were used because that had previously been decided as was it gave most reasonable results in the preliminary experiment.
Conclusion
From these experiments I decided that I will use 3 medium chips in the main experiment because it gave a time not too high and not too low, and so the risk of difficulty and shortage of time will not be present in the main experiment. Similarly I chose to use 25cm3, because this too gives a time slow yet not too fast.
Aim
The aim of the experiment is to investigate how the rate of reaction differs as the concentration of hydrochloric acid varies.
Safety
- Wear safety goggles to protect my eyes from any harmful chemicals.
- Taking care when handling chemicals, particularly Hydrochloric acid because it is an irritant.
- I will not touch my eyes or mouth until I have washed my hands thoroughly with soap after conducting the experiment.
- Taking care when using glassware to prevent injury.
-
4 mol/dm3 is the most concentrated solution I will use. This is because a solution with a higher concentration will produce a lot of acidic fumes.
Apparatus
- Measuring cylinder - To measure the volume of the acid.
-
Stopwatch – To measure how long it takes for 50 cm3 of carbon dioxide to be given out.
- Safety goggles – To insure that in the case of accidents products do not reach my eyes, because hydrochloric acid in particular is dangerous to the eyes.
- Calcium carbonate; marble chips of different sizes – so that the constant (the size of the chip) can be decided.
- Hydrochloric acid – To react with the calcium carbonate.
- Bung – To allow the carbon dioxide gas to pass along to the gas burette.
- Conical flask – Where the reaction between the marble chips and hydrochloric acid will take place.
- Trough – Enables carbon dioxide gas not to escape so that it can be measured.
- Clamp – To securely hold the gas burette.
- Gas burette – To contain the carbon dioxide gas so that it can be measured.
Method
- We filled up the trough and gas burette with water to the top.
-
Then we filled the conical flask with 25 cm3 of hydrochloric acid.
- Following this the gas burette was placed on a clamp and was placed facing downwards so that the open end was inside and surrounded by water.
- We then placed the delivery tube in a position where it was directly beneath the gas burette and also was going through the bung.
- Three marble chips (weighing a total of 1 g) were dropped in the conical flask and the bung was immediately placed on the flask while the stopwatch was started.
- After that we recorded the amount of carbon dioxide that was produced every 10 seconds.
Precision And Accuracy
For this experiment precision and accuracy needs to be maintained when obtaining the results. In other words our results need to be as near to the true value as possible:
- In the experiment we will be using a measuring cylinder that has divisions for millimeters placed on it. This means the water displacement will be accurate as measurements will be correct to the nearest millimeter.
- A range of different concentrations of hydrochloric acid were used for the main experiment, because this gives us a variety of results and therefore a better understanding of the experiment.
- At each concentration of hydrochloric acid three results were collected, and then an average was created. This allows any anomalous results to be easily spotted and taken out, and so the results are more accurate.
N.B. Three medium sized chips were used for the main experiment and 25 cm3 was the constant volume of hydrochloric acid used.
Average Results