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How higher or lower concentration and temperature affects rates of reactions

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Introduction

How higher or lower concentration and temperature affects rates of reactions Parasto Aghazadeh Parisa Aghazadeh Ahmed Laajam Mohit Parkash Chemistry A Mr.Hatton N1A IEGS Aim; The aim of this lab is to investigate the rate on the reaction between sodium thiosulphate and Hydrochloric Acid, when the values of concentration and the temperature is either decreased or increased of the Hydrochloric Acid. Background; The definition of a reaction is when two or more reactants connect to form a new precipitate. The rate means how low/fast something takes place and it is the measurement of time and change that happens in a component. The rate can be used in any suitable measurements such as seconds, minutes and even hours. For these reasons the rate of a reaction means how fast/low it takes for the reactants to form a new precipitate. Hydrochloric acid and sodium thiosulphate are both clear and colorless liquids, but in the reaction between them a precipitate of yellow and cloudy sulphur forms to measure the rate of the reaction. The aim is to time how long it takes for the reaction to form the actual precipitate. The faster the reaction appears, the faster the mixture gets cloudy. Hydrochloric acid is a solution in water containing hydrogen chloride (HCL). The solution is very corrosive and it is found naturally in gastric acid, which is a digestive liquid produced in the stomach. ...read more.

Middle

At the same time turn on the stopwatch and the magnetic stirrer. To get more accurate results be consistent with the spinning strength of the magnetic stirrer. 9. Stop the stopwatch when the cross is no longer visible and record the time onto the results table. 10. Wash the conical flask with distilled water. 11. Repeat the steps 4-10 three more keeping the same temperature. 12. Find the average of the two results. 13. Repeat 4-11, keep changing the temperature according to the template, see table 2. Results; Calculating moles of different concentrations: Volume of HCL acid (cm3) * Original concentration (M) / Total volume (10 cm3) 1st - 3rd trial --> 10 * 1 / 10 = 1 mole 4th - 6th trial --> 7.5 * 1 / 10 = 0.75 mole 7th - 9th trial --> 5 * 1 / 10 = 0.5 mole 10th - 12th trial --> 2.5 * 1 / 10 = 0.25 mole Concentration Time taken (average) Rate of reaction 1 M 49.8 sec 1 / 0.83 = 1.20 0.75 M 61.8 sec 0.75 / 1.03 = 0.72 0.5 M 66.0 sec 0.5 / 1.1 = 0.45 0.25 M 82.8 sec 0,25/1.38= 0.18 Temperature Time taken (average) Rate of reaction 15 oC 122.5 sec 15 / 2.04 = 7.4 Room Temperature 65.4 sec 22.5 / 1.09 = 20.64 40 oC 49.8 sec 40 / 0.8 = 50 Conclusion; The results do support our hypothesis about the concentration. ...read more.

Conclusion

To avoid contaminating the substances used during the lab, one member of the group had to clean all equipments used, properly and thoroughly. When cleaning, distilled water and normal tap water was used, distilled water was only used on the equipment in a lot of contact with chemicals. If the equipments are not cleaned properly or not cleaned at all there could be some chemicals or residue left on the equipments. Then the substances used during the lab would later be contaminated if dirty equipments are used, this would thereby lead to inaccurate results. By cleaning all equipments used during the investigation the factor of getting inaccurate results due to contamination was cleared. After cleaning the equipments it was made sure that no water was left since this could lead to contamination as the water could interfere with the substances used during the investigation, this was resolved by wiping the water with a peace of cloth. Overall we are pleased with the results and the way the experiment was carried out. The results were fairly accurate because we repeated it three times and then took the average, and the results did prove our hypothesis as well. To make this experiment more interesting we would like to also investigate other factors which affect the rate of a reaction, for example using a catalyst and also to have a bigger/smaller surface area to see how they affect the rate of a reaction as well as getting a fully understandable knowledge of which of the factors does affect the rate of a reaction the most and why. ...read more.

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