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An investigation into how concentration affects the rate of a chemical reaction.

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Introduction

An investigation into how concentration affects the rate of a chemical reaction Aim To investigate how concentration affects the rate of reaction we will be reacting calcium carbonate and hydrochloric acid. To make this a fair test we will have to keep all variables the same except the one we are investigating. The products of the reaction between calcium carbonate and hydrochloric acid are calcium chloride and carbon dioxide. To measure the rate of reaction we will be measuring the volume of carbon dioxide produced. The equation for this reaction is: CaCo3 + 2HCL CaCL2 + H2O + CO2 Variables The variables that may have an affect on this experiment are: Size of marble chip- the size of the marble chip will affect our experiment because this dictates the surface area. The larger the surface area the more acid that will be in contact with the hydrochloric acid and able to react. Concentration of hydrochloric acid- this is the proportion of hydrochloric acid in the solution. Volume of acid- this will be the amount of hydrochloric acid that will be reacted with the marble chips. Catalysts- by weakening bonds these increase the rate of reaction by lowering activation energy a catalyst will not be used in this reaction, however. Mass of marble chips- The mass of the marble chips is a way of measuring the quantity of chips being used. Temperature- the temperature adds energy to the reaction an affects how quickly the particles move. ...read more.

Middle

this to put the cylinder of water upside down in so water does not spill Delivery tube- this will be used for the gas to travel down and will be useful because we will not have to hold the conical flask. Scales- this will be used to measure CaCO3 Stopwatch- this is needed to measure when the volume of gas needs to be recorded. Method In this investigation we will be recording the volume of gas every thirty seconds because this was a suitable time interval for finding a measurable change to take place. The time we will be measuring this experiment for is three minutes because this gave us enough data for us to draw an accurate graph and we would not have to wait too long to complete one experiment. This gave us time to repeat the experiment three times so we would have more accurate averages. We will be measuring the cylinder to the nearest cm� because this is how often the cylinder is marked so this is the most accurate we can get. The time will be measured to the nearest millisecond we will not be able to record the volume at exactly this time though so we will probably measure the time to a two second accuracy. To make the test a fair test we had to carry out the same method each time this is what we did. ...read more.

Conclusion

To solve this problem we could use a gas syringe but the problem with this is we could not test the higher volumes of gas, which would mean the range of results would be lower which would mean the pattern we got would be less obvious. The experiments were fair tests to a certain extent but there was a certain margin of error because the results recorded were only to the nearest cm� and the values of the controlled variables were not exact amounts so the may have been slightly differently each time which would have affected slightly the reliability of the results. This would have made little difference to the results though as the volume of gas was only measured to the nearest cm�. To find if the prediction was supported or to find if the reaction rate did slow down after the time progressed the experiment could be timed for longer than two minutes. This would also enable us to find weather the pattern changed after a certain time or the reaction rate just generally slowed down and we found a curve when comparing the concentration of the acid and the calcium carbonate. It was also not certain if the concentration keeps increasing the rate of reaction or this only happens to a certain extent. This could be found out by extending the range of concentrations reacted. These reactions would have to conducted very carefully though as hydrochloric acid of this concentration can be very dangerous. Paul Gregson Littlemoss High School Science ...read more.

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