Rate of reaction between Calcium Carbonate and Hydrochloric Acid

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                                                                                                                   Prasal. S. Rohra- X-B

Rate of reaction between Calcium Carbonate and  

                         Hydrochloric Acid

Aim:

To investigate whether the concentration of hydrochloric acid affects the amount of carbon dioxide given off by marble chips while reacting with the acid. This is the word equation for my investigation:

Hydrochloric Acid + Calcium Carbonate => Calcium Chloride + Carbon Dioxide + Water

Introduction:

A collision between particles is needed for a reaction to take place in order to form a product. Some collisions are successful and give a product while others do not because particles do not have enough energy.

 A theory named ‘The Collision Theory’ states that when there is a higher concentration, there are more particles therefore there are more collisions resulting in a higher reaction rate. This also applies to my experiment because, as the concentration of the acid increases, there are more acid particles in the same volume. Therefore there is a greater chance of acid particles colliding, and reacting with more particles on the surface of the marble resulting in a faster reaction and production of carbon dioxide.

Therefore when the concentration doubles, the number of particles that are able to collide are also doubled therefore the rate of reaction also doubles until the particles are used up and the reaction slows gradually to a stop.

The experiment to be conducted will use CaCO3 and HCL to produce => Salt + Water + Carbon Dioxide.

Hypothesis:

I hypothesize that increasing the concentration of an acid increases the number of collisions between particles, therefore, the rate of reaction increases. The increase will be proportional.

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PLAN-

Variables:

Dependent-

  • the Rate at which CO2 is produced

Independent-

  • Concentration of HCL

Controlled-

  • Volume of HCL
  • Apparatus
  • Mass of Marble Chips

Apparatus:

  • 1 x Digital Balance
  • Paper
  • 5 x 50ml Beakers
  • 1 x 150 ml Beaker
  • 1 x Large Plastic Container
  • 1 x Stopwatch
  • 2 x 50ml Plastic Measuring Cylinders
  • 1 x Conical Flask
  • 1 x Rubber/ Plastic Tube
  • 1 x Rubber Bung
  • HCL of concentrations - .2 molar, .4 molar, .6 molar, .8molar,  

                          ...

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There was only one typo in the whole piece of work and it was writing “then” instead of “than”. This perhaps shows that more care needs to be taken when proof reading over coursework. The student has used the appropriate scientific terms required for GCSE however, as noted before, they should be using superscripts and subscripts where appropriate and not side stepping this by writing it without. However, one term that the student lacks understanding of is the difference between accuracy and reliability. It is very common for GCSE students to get them mixed up but accuracy is related to the scale on the measuring instruments whilst reliability is whether the results are consistent (i.e. repeatable). Whilst both are very similar, it is important to learn the definitions. The student has produced a very high level piece of work and shows very good understanding of the experiment and therefore their answer was very well developed and supported.

The analysis needed for this piece of work was analysing the results obtained and then comparing it with the hypothesis that they came up with beforehand. The student did this very well and their clear structure and layout helped immensely to guide the examiner through the experiment conducted by the student in order to answer this question. Their judgement (reviewing their hypothesis) was very well done. The student acknowledged the mistakes and changed them accordingly by using the experimental data obtained to support the changes made. The use of diagrams helped guide examiner through the work as well and made it easier to understand exactly what was happening. One striking thing in their evaluation for improvements was their statement of taking more safety precautions and therefore suggesting the usage of goggles. Especially when handling acid, I believe it is imperative that a student wears goggles when conducting the experiment. Truly, I do not believe that a teacher would put the student at risk by allowing them not to wear goggles. This one piece of information suggests that the student perhaps lacks the basics in understanding that acids are an irritant and can be very harmful if there is eye contact with it and depending on its concentration, any contact at all.

The student has answered the question set very well and it is very clearly and logically laid out. This helps the examiner identify the relevant points more quickly and helps the student present a coursework that is fluent and well structured. However, my main criticism of this piece of work is that the absence of using the subscripts or superscripts in word processing the piece of work. Strictly speaking, writing CaCO3 is incorrect. Another point I found was that the student used HCL as the formula for hydrochloric acid of which is wrong as it should be HCl – special care should have been taken to not allow the auto correct of the word processing program used to correct it, if this was the case. Yet despite this, this was a piece of work at a very high standard and the student clearly shows a strong understanding of the question set.