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  • Level: GCSE
  • Subject: Science
  • Essay length: 2591 words

Investigating the Rate of Reaction - Sodium Thiosulphate and Hydrochloric Acid

Extracts from this essay...

Introduction

Investigating the Rate of Reaction - Sodium Thiosulphate and Hydrochloric Acid Aim: To find out how the rate of reaction between Sodium Thiosulphate and Hydrochloric Acid is effected by the change of concentration. I am investigating the rate of reaction between Sodium Thiosulphate and Hydrochloric Acid. There are five factors which effect the rate of reaction: temperature and concentration of the reactants, pressure (in gases) and the surface area of any solid reactants. The rate of reaction is the rate of loss or the development of a product during a chemical reaction.The input variable will be the concentration, the constant variables will be the Hydrochloric Acid and the solution and the dependent variable will be the temperature. After doing some preliminary experiments, I have decided to investigate the effect of concentration on the rate of reaction. The reasons for this is that it is more practical and will be the best way to get the most accurate results. Temperature is extremely difficult to get exact results as they can always change depending on room temperate. Equipment - Beaker - 2 Measuring Cylinders (large and small) - Stopwatch - Pipette - A black cross - Sodium Thiosulphate (in different concentrations) - Dilute Hydrochloric Acid (has the same concentration every time) - Water (different concentration) Prediction I predict that if we were to change the temperature of the Sodium Thiosulphate, the higher the temperature is and the faster the rate of reaction will be.

Middle

3 49 seconds Concentration Volume Experiment No. Reaction Time 10cm3 - HCL 1 63 seconds 30cm3 - Sodium 2 67 seconds 20cm3 - Water (H2O) 3 65 seconds Method Firstly, we had a bold black cross on a laminated piece of paper and placed it on the lab desk. Then, we put 10cm3 of dilute hydrochloric acid in a large beaker and placed the beaker directly on top of the black cross so we could see the cross clearly when looking inside the beaker. We then added 50cm3 of Sodium Thiosulphate to the dilute hydrochloric acid and as this was the first test, we did not use any water. As soon as the dilute hydrochloric acid hit the sodium in the beaker, we immediately started the stopwatch. We then kept a close eye on the pale yellow mist getting stronger and waited until the cross was completely obscured by the substance. As soon as we could not see the cross anymore, we stopped the stopwatch and recorded the result time in seconds. The contents of the beaker was then thoroughly emptied and cleaned along with the measuring cylinders to use again for the next test. Next, we added 40cm3 of Sodium Thiosulphate and kept the hydrochloric acid constant at 10cm3. Because we kept the volume of this the same, to make it a fair test we added 10cm3 of water to make it equal. The sodium thiosulphate and water was added at the same time to make it fair.

Conclusion

This was difficult as the cross disappears in different parts of the beaker and there is still some clear patches left so, it was difficult to find a point to stop the stopwatch at the right time. The experiment was done over 3 hours. One of the best methods to work out the rate of reaction equation is to find out the concentration of the solutions after different time intervals. The concentration of reactants after a given time interval is unknown which is why this method was not used. The school lab only has basic equipment and doesn't have the detailed technology and equipment that we would be able to measure the concentration of a reactant after a given period of time. In conclusion, I have found out that the more concentrated a reactant is, the quicker the rate of reaction time will be. My results give evidence of this because as the amount of Sodium Thiosulphate decreases and the amount of water in the solution there are less atoms to collide and therefore, less successful collisions causing chemical change so the reaction rate is slower. In more concentrated solution, there are more atoms to collide so the reaction time is faster. Overall, I think this experiment has been successful. I have learnt and proved that concentration does affect the rate of reaction. As well as this, I have found that one of my predictions we're correct and one wasn't. I think the results could have been more accurate with more expert equipment and that there could be a lot of human errors in this experiment. Rebecca Scott Rebecca Scott

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