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Investigating the change of rate of reaction with change in concentration.

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Investigating the change of rate of reaction with change in concentration Aim: To examine the effect the concentration of the reactants has on the rate at which they react (i.e. the rate of reaction). Reactants and Products which will be investigated: Sodium + Hydrochloric Sodium + Sulphur + Sulphur + Water Thiosulphate Acid Chloride Dioxide Na S O + 2HCL 2NaCl + S + SO + H O This reaction between sodium thiosulphate and hydrochloric acid (both colourless) yields a yellow precipitate of sulphur along with other by-products (e.g. water). Therefore using this knowledge we are able to investigate the effect various dilutions of the reactants (either sodium thiosulphate or hydrochloric acid) have on the rate at which they react. During this investigation the concentration of sodium thiosulphate will be diluted while the concentration of other reactants will remain constant. The rate of at which the two reactants react will be indicated by the time in which the yellow-coloured sulphur is precipitated. Prediction: Through moderate understanding I predict that the greatest concentration of either reactant should equate to a faster rate of reaction (i.e. ...read more.


Wash out the flask thoroughly . 7. Repeat the experiment using the volumes of sodium thiosulphate, hydrochloric acid and water outlined in the table below. Diagram: Before Reaction After Reaction Results: Volume of sodium thiosulphate (cm�) Volume of hydrochloric acid (cm�) Volume of water (cm�) Time for cross to disappear (sec) Concentration of sodium thiosulphate (mol/cm�) 50 5 0 20 0.15 40 5 10 26 0.12 30 5 20 60 0.09 20 5 30 100 0.06 10 5 40 400 0.03 CONCLUSION- Analysis: The graph primarily indicates that as the concentration of sodium thiosulphate increases, the time taken for the reactants to react reduces, i.e. a greater concentration equates to faster rate of reaction; thus my prediction was accurately composed. However theoretical analysis illustrates that the concentration of reactants should be indirectly proportional to the time taken for them to react i.e. concentration is linear to 1 . time taken My graph/results do not a show an absolute indirect proportionality between the concentration and the rate of reaction (which was indicated by the time taken for the cross to disappear). ...read more.


This was subsequently due to inaccuracies in the results. Inaccuracies would have originated from the temperature of the sodium thiosulphate which was used. At the beginning of the investigation and through to obtaining the results for concentration 0.06mol/cm�, the sodium thiosulphate was at approximately room temperature. However the sodium thiosulphate used for obtaining the final concentration was taken out of the fridge and thus was at a much lower temperature. This would have had a huge impact in our results (which has been outlined on the graph). The amount agitation which was given to the each conical flask as the reactants reacted may project slight inaccuracies in the results In order to achieve more promising results, the readings should be obtained more accurately (e.g. time for cross to disappear) and set amount of trials should be initiated for each concentration which was investigated. The temperature of reactants should remain constant throughout experimentation. Unfortunately from the inaccurate results which were obtained we could not draw an absolute firm conclusion. However we were able to equate on an elementary basis, that as the concentration of the reactants increases, the rate of chemical reaction increases. Shozab Raza 10B ...read more.

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