Investigating the factors which affect the rate of reaction between (CaCO) and HCl

Investigating the factors which affect the rate of reaction between (CaCO₃) and HCl

Introduction

In this course work I predict that the higher the concentration, the faster the rate of reaction, due to the collision theory which states for a chemical reaction to occur, particles must collide with each other in the correct way and also have enough energy for the collision to be successful’

METHOD:

I shall then begin to take measurements every 30 seconds after I have added the marble chips to the acid and measured how far the gas syringe has moved. By doing this I will know how much gas has been produced from the reaction, because when it is produced it goes through and the gas syringe moves backwards. Various factors affect reactions. If you increase the surface area of a solid, the rate of reaction will increase

Temperature:

When the temperature of the acid is increased, more energy is produced as the molecules collide a lot more. Then more they collide, the more likely they are to combine. When the temperature is dropped the molecules do not collide as much as the molecules are moving slowly. Therefore, the higher the temperature, the quicker the rate of reaction.

Concentration

In a reaction , if there is more of a substance then the probability of the molecules of colliding is a lot higher and therefore will speed up the rate of reaction. Then obviously if there is less of a substance then the reaction will happen at a slower rate.

Surface area

If the chips are broken up as a powder then they would have a larger surface are and so the rate of the reaction would speed up due to the fact that the bonds are easier to break as the more of the acid has more access to the powder. The bigger the chips, the harder it is for the acid to dissolve the chip so the slower the rate of the reaction.

Hydrochloric acid+ calcium carbonate calcium chloride + carbon dioxide + water.
2HCl(aq) + CaCO3(s) CaCl2(aq) + CO2(g) + H2O(l)

Various factors affect reactions. If you increase the surface area of a solid, the rate of reaction will increase. To do this, instead of using a lump of Calcium carbonate, you could use powder. This would be investigated by using a lump of CaCO₃, various sizes granules, until you would reach powder form.

Another variable could be temperature. If you increase the temperature, the faster the reaction will be. For the above experiment, I would only be allowed ...

This is a preview of the whole essay

Hydrochloric acid+ calcium carbonate calcium chloride + carbon dioxide + water.
2HCl(aq) + CaCO3(s) CaCl2(aq) + CO2(g) + H2O(l)

Another variable could be temperature. If you increase the temperature, the faster the reaction will be. For the above experiment, I would only be allowed to heat the solution to 70°C, for safety purposes.

The third variable is concentration. Concentration is measured in M (moles per dmˉ³). Therefore, 1M is equal to 1 mole of Hydrochloric acid, and 1 litre of H₂O. The concentration can only be a variable if the substance can be dissolved in water. In this instance, the higher the concentration, the faster the reaction

A reaction occurs when particles collide. This process is based on random particle movement. so therefore, the more particles you have in a space, the more likely they are to collide. Therefore making the reaction accelerate.

This theory can be proved if you compare the rates of reaction with marble in hydrochloric acid. 'If the acid is of a higher concentration, the reaction will be quicker.'.

Also if the particles have more energy, they will be travelling faster, making them collide more frequently.

The variable

I had to acquire 6 different results for each variable. The first time I tried 0.5 m with a small chip size so then I used a different concentration of acid but I kept the same volume through out the experiment. I then measured in between 0.5 and 1.0 (0.75) and that gave a good result I then tried the first concentration of 0.5 with the large sized chip but it took to long but as I increased the concentration the reaction sped up.

My variable was the concentration of the acid; it varied from 0.5M to 2.0M

I mixed the different concentrations of acid with water.

I tried 0.25M but the reaction was to slow. I did six sets of results for the small size chips and then another six results for the larger sized marbles.

Analysis

My results generally show what is was expecting to se in my experiment. Apart from a few minor exceptions my results follow a general pattern which supports the collision theory which states ‘for a chemical reaction to occur, particles must collide with each other in the correct way and also have enough energy for the collision to be successful’. My results support this and so from my results I have concluded that that concentration affects most rate of reaction so the higher concentration the faster the rate of reaction. This is because particles are more concentrated so there are more successful collisions, which cause a greater rate of reaction. From the experiment we can conclude that the rate of reaction is increased with the concentration of the acid. I found that as the concentration increased the rate of reaction increased. The reason that the reaction was quicker was due to the collision theory. There are more particles in the acid as the concentration increases so there are more particles to collide. I found that as the concentration increased the reaction speed was increased because there were more particles to collide the speeding up the reaction. On my 0.75 molar the reaction time should have been slower than the other molars but it wasn’t. This may have been because I added to many chips for that run though. Also on the final result, it may not have been accurate as it was very hard to time because it was going very fast.

All my experiments went well except run 5 (1.75 M). The reason this was not successful was because the gas syringe I was using got stuck. On graph it is clearly noticeable that the gradients are steeper the faster the rate of reaction.

Evaluation

Measurement errors

Measuring cylinders as I could be above or below the line by maybe one or two millimetres.
Syringe may have been a problem as I may have stopped the experiments a millimetre or two before the end of the syringe.
I could have made a measurement error when I was filling up the beaker as some acid could have splashed out causing the experiment not to be accurate.
When I added the acid to the chips in the beaker the reaction started at once and there may have been some acid lost when I was putting the bung on.
The syringe may have had a small chip in it causing gas to escape
I could have weighed the marble chips incorrectly which could have let to an increase in gas being produced thus causing the reaction to speed up because there are more particles colliding.
It was very hard to count the seconds with the higher molar concentrations so I may have stopped the stopwatch to late, or early.

Most of the predictions that were made in the coursework planning section have been proven correct because in all cases in my experiment the concentration of the marble chips has altered the rate of reaction. The reason for this is that concentration is one of the factors that affects rate of reaction and so my prediction about more gas being produced with higher molar acid is correct. From the graphs and the results tables I can see that the higher concentration is the faster the rate of reaction. So for higher concentrations the lines on the graph were steeper than for lower concentrations. This also means that the higher the concentration the steeper the gradient. The reason for this is the major role of activation energy which is very much part of the collision theory because this energy decides whether a collision will result in a reaction and whether a successful reaction will take place.