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Chemistry Rate of Reaction Coursework for Calcium Carbonate and Hydrochloric Acid

Free essay example:

Investing Rate of Reaction

I am going to investigate the rate of reaction between two substances: calcium carbonate and hydrochloric acid.
Rate of reaction measures the speed at which a reaction takes place. This is measured by;
rate of reaction =    
amount of reactant used or amount of product formed
                                                                     time taken

As seen above, there are two ways to measure a rate of reaction ;
1) measure the rate at which the reactant is used up,
2) measure the rate at which the product is formed


Different reactions can happen at different rates. Reactions that happen slowly have a low rate of reaction. Reactions that happen quickly have a high rate of reaction. For example, rusting has a low rate of reaction. Explosions have a high rate of reaction. A reaction must be at a convenient speed to measure, because a fast rate of reaction can be hazardous, and a very slow rate of reaction is not practical.

The Equation for the Reaction

Calcium carbonate + Hydrochloric acid                      Water + Carbon dioxide + Calcium chloride     

REACTANTSPRODUCTS

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

How to measure the rate of reaction

Using a gas syringe



This method measures the gas product of the reactants. The gas syringe has marks along its length
which allow the volume of collected gas to be measured.
The increase in volume can be timed, and a graph of volume against time can be plotted.
This shows the
rate of the reaction. image00.png

Equipment: a gas syringe, rubber bung, conical flask, stand, clamp, 25ml hydrochloric acid, 2g medium sized calcium carbonate pieces, and a stopwatch.

Method; 
1) The gas syringe should be set up horizontally by an attachment to the stand, by the clamp. The tubing should be positioned well on the rear end of the gas syringe.

2) Place calcium carbonate in conical flask, and quickly pour in hydrochloric acid. The rubber bung should be placed extremely fast after this process, as well as the starting of the timer. The gas molecule products produced from the reactants in the flask are transferred from the flask to the gas syringe by the tubing by the movement of gas. The gas products are carbon dioxide and calcium chloride.  

The pressure in the gas syringe is built up because of the air-quality of the gas syringe, where it is air tight. This pressure is realised by a push forced onto the plunge inside of the gas syringe, which shows the exact ml of product produced to be visible by the scale of measurements on the outside of the gas syringe.

Reliability

Good assets

This method of measurement in products is extremely easy to measure and set up. It’s also very easy to reset, and is pretty advanced compared to some other methods, like for example timing and observation, where the reliability depends on the quality of eyesight, which is never 100% accurate and will vary with different individuals. In other terms, there’s less dependence on human ability, which can easily cause an error. This method proceeds in a reliable and scientific manner whilst also being easily set up and measured.

Bad assets

Compared to, for example, timing and observation, this method is harder to set up and takes away time which could’ve been used to record more results, therefore providing more reliability. However, unlike timing and observation, this method is far more accurate, so a result or two less would not be much trouble. In this method, there is quite a lot of equipment used, which makes the scientist depend on the equipment, and it not failing or breaking.

Timing and observation

This method is simply done by looking and timing for a particular interval, i.e. 30 and 60 seconds.

Equipment: flask, reactants, and timer.

Reliability

Good assets
This method is easy to set up and reset. The time availability given by the easy set up allows more time for more results, which means a fairer range.

Bad assets
This method is unreliable due to the fact it is dependent on human eye sight, which can never guarantee accuracy.


Measuring volume of gas in products by displacement of water

Water is where if you put an element in water, the amount of water displaced (thrown out) is equal to the volume of that element- so by measuring the overflow of water; you can work out the volume of the object (it only works if the object is non-porous).

Equipment:  a conical flask, rubber bung, rubber tubing, water tray, measuring cylinder, the reactants, bee hive shell,  white paper, delivery tube, and a stopwatch. image01.png

Method

1) The equiptment for this method is set up by attaching the bung and rubber tubing to the flask, and then placing the tubing underneath the beehive shell, which then is inserted into the cylinder, which should be full of water (by careful procedure). This whole method (apart from the flask and part of the tubing) should be carried out in a water tray, full of water.
2) The calcium carbonate is mixed with the hydrochloric acid in the conical flask. The timer starts straight after this.
3) As the reaction takes place, the gas products move towards the measuring cylinder, where the water is replaced with the gas molecules. At the end of the experiment, (i.e. a 30 or 60 second interval), the scale on the cylinder shows the amount of water lost, and so therefore, the amount of gas gained.

Reliability

Good Assets
This method produces rather reliable and scientific results, if, of course, it is set up properly to measure. 
This method does not require skill since it is dependent on the equipment.

Bad Assets
This method was hard to handle, set up, and reset. The CO2 can also dissolve into the water, which isn’t practical. It is dependent on the equipment, which also widens more room for error in the equipment used. It is also time consuming, which isn’t practical. image02.png

Observation of precipitation
The process of making a solid from a solution is called precipitation.
The solid itself is the precipitate.
An insoluble product can be made by reacting the soluble reactant
with an
acid or alkali.

Equipment: reactants, paper, conical flask, and a stopwatch.  

Method:

1) The reactants are mixed in the conical flask. Underneath of the flask, an ‘X’ is marked onto the paper, in the middle.

2) As the reaction proceeds, the ‘X’ gets harder and harder to see because of precipitation taking place. When the ‘X’ is no longer visible, the timer is stopped and the timing is measured.

Reliability

Good Assets
This method is easy to set up and reset, especially compared to a lot of the other methods like the displacement of water and gas syringe. The simplicity of this method does extent the time availability, which allows more results to be carried out. More results do mean a fairer average.

Bad assets
This method did not prove such reliable measurements and results seeing as the observation would have to be done using human activity, especially eyes instead of a reliable apparatus. It would also give a limited range of results.  The main con of this method is the variation of eyesight used, meaning low quality of eyesight isn’t practical, and the different interpretation of when the ‘X’ is no longer visible is also unreliable.

Measuring loss of mass
This method works by measuring the loss of mass as a as forms. Cotton wool is inserted.

Method:
1) The flask is put upon the top pan balance, and it is reset to 0, so that the weight of the flask is not included (only the weight of reactants). 
2)The reactants are set up and mixed. The timer is started straight after. The mass should lower as the time increases.

Equipment: reactants, a cotton wool plug, conical flask, timer, and a top pan balance.

Reliability

Good assets:
This method is easy to set up and reset, as well as to time (like most of the other methods). The easy set up allows more time for more results which allow a fairer mean.
No human skill is needed here like for example eye sight, because this experiment is equipment reliant, which therefore decreases the chances of an error.
image03.jpg

Bad assets:
The measurement of the experiment would be difficult. Also, the fact that we have to reset it to 0 at the start, whilst the reactants are already reacting, provides unreliable timing, and therefore unreliable results.

Conclusion

After trialling all of the methods for measuring the rate of reaction, I have formed a clear view of the reliability of each method, and the practicality.
In general, the human dependent methods turned out to be the least feasible, i.e. timing and observation, and observation of precipitation. In the science industry, a human reliant factor would be extremely impractical because of the lack of accuracy. Although these methods were far simpler than the rest, they were also the least reliable. This is why I reject these two methods.
The measurement of mass as a gas forms was also another easy yet impractical method, because the hassle forced on the scientist before the timer had to be set was far too much. The fact that the reactants had already started to react whilst the timer hadn’t even been set yet due to the fact the top pan balance had to be reset was an extremely unreliable factor. I therefore reject this method of measurement.
The available methods left are the gas syringe method, and the displacement of water, which compared to the others, turned out to be the most practical, reliable and innovative ways of measurement. These methods were equipment dependent, which is a much more accurate asset than them being human dependent like most of the rejected methods. The displacement of water method provided reliable results, produced by a scientific method. However, the set up of the method was the hardest out of all the other methods, and required attention. The increased number of equipment used provides a more equipment dependent method, which, if one part of the equipment fails, so will the whole method. I reject this method purely and simply because of the hassle of equipment and the time absorbing attention it required. I also reject it because the carbon dioxide produced from the reactants can dissolve in the water which provides unreliability. The only method left to use is the gas syringe, which appeared to be the most reliable and feasible to set up, as well as being a scientific way of measuring. The setting up of this method does not require so much hassle or attention, yet the procedure of measurement provides accurate results. This is why my chosen method for measuring the rate of reaction is the gas syringe method.

This student written piece of work is one of many that can be found in our GCSE Patterns of Behaviour section.

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Here's what a teacher thought of this essay


This is a well written and researched piece of investigation. It is supported by clear figures that add to the textual information provided. It is two stars as it only covers the initial research into the appropriate method. This could not be submitted as it is incomplete.

Marked by teacher Cornelia Bruce 18/04/2013

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