Rates of Reaction Course Work.

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Rates of Reaction Course Work

Introduction/Aim:

 This coursework is about the investigation of the effect of concentration on the rate of reaction between Sodium Thiosulphate (Na2S2O3)  and Hydrochloric acid (HCL) by simply changing the concentration of Sodium Thiosulphate. I made a set of results which were obtained by using the method of ‘precipitation’. This is when the product of the reaction is a precipitate, which clouds the solution. One observes a marker through the solution and measures how long it takes for it to disappear.

 

Plan:

In order to make it a fair test the volume of hydrochloric acid had to be kept constant each time (5cm³).  What had to be changed was a) the amount of Sodium Thisulphate and b) the amount of water. We decided our total volume to be 55 cm³, 5 cm³ of that hydrochloric acid, so the rest consisted of Sodium Thisulphate and Water. To obtain our resultes we used the following "Method":

Step 1:

After setting up everything we first used a measuring cylinder to measure the amounts of Sodium Thiosulphate, Water and Hydrochlorid acid needed. We put the added amount of water and thiosulpahte (which has to be 50 cm³) into a connical flask which will be placed on a paper marked with a cross ("X").

After that we take the measuring cylinder with the 5 cm³ of HCl and pored it into the conical flask.

Step 2:

The stopwatch was started as soon as the first drop of HCl got in. We did this in order to estimate the time how long it took until the reaction was comletet. The mixed solution was first clear, but as time went by it got gradually more and more cloudy because of the many reactions taking place in the solution. so that´s why we started to take the time when the solutions were just mixed together until a point, where the mixed solution has reached a point, where the solution has a specific ‘cloudiness’ and we couldn`t see the cross anymore.

 

In the beginning of step 1, I mentioned that the investigating person had drawn a black cross under every flask before every experiment. These black crosses were there to show the person, how long the reaction took, when he took the time the time. The diagram above is there to give you a better picture, how he knew, when the reaction has reached a certain point. In the beginning, the solution is still clear and it is easy to view the black cross, but as times goes bye and the reaction goes under way, the solutions gat gradually more and more cloudy, which means that it gets harder and harder to see the cross. As soon as one cannot see the black cross anymore, the solution has reached a certain point of cloudiness and the time is stopped. All of the results were recorded in a table.

Step 3:

In the next experiment the concentration of sodium thiosulphate is either reduced or increased to a certain limit in order to investigate the rate of reactions when the concentrations were changed.   

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To get a whole set of results the experiment had to be repeated with all the different concentrations and after that, to get a second run we repeated the wohle procdure.

Apparatus:

  • Measuring Cylinders                        -used to measure the volumes of the solutions
  • Stopwatch                                -used to record the times
  • Conical Flask                                -used to hold the solutions
  • Permanent black marker                        -used to label the flask and to draw a cross
  • Thin glass stick                                -used to mix the different solutions together
  • Sodium Thiosulphate
  • Hydrochloric Acid

Safty:

There are a few things that you should do in ways of saftyness ...

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