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The determining of a rate equation from the reaction of sodium thiosulphate with hydrochloric acid - page 2
Keywords: The determining of a rate equation from the reaction of sodium thiosulphate with hydrochloric acid
By Carlitob10 on 04/11/2006 11:57:07
Level: A Level (Year 13)
Page Number: 2 of 8 pages: 1 2 3 4 5 6 7 8hydrochloric acid and sodium thiosulphate, I will change the concentration of the reactants one at a time to simplify my study. When the concentration of the sodium thiosulphate is altered, I will keep the concentration of HCl constant throughout the investigation and vice versa. Keeping the total volume of the reaction mixture the same is to ensure that the concentration of HCl or sodium thiosulphate, depending on which I am varying, would remain constant therefore allowing me to properly observe the effect of changing the concentration of one of the reagents to ensure a fair test.
From analysing the preliminary experiment I have decided to use these concentrations for the HCl when I am varying it:
Volume of HCl (cm3) Volume of water (cm3) Concentration of HCl (mol dm-3)
25 0 2.0
20 5 1.6
15 10 1.2
10 15 0.8
5 20 0.4
2.5 22.5 0.2
1.25 23.75 0.1
And these concentrations for the sodium thiosulphate when varying it:
Volume of thiosulphate (cm3) Volume of water (cm3) Concentration of thiosulphate (mol dm-3)
40 0 0.4
35 5 0.35
30 10 0.3
25 15 0.25
20 20 0.2
15 25 0.15
10 30 0.1
The reason for choosing these particular concentrations was because of the time it took the preliminary experiment to complete which was 15.86 seconds. I did not want to use too high or too low concentrations so that the times for the experiments were neither too long nor too short, as this would affect accuracy.
Constants
Temperature
Usually, an increase in temperature is accompanied by an increase in the reaction rate. Temperature is a measure of the kinetic energy of a system, so higher temperature implies higher average kinetic energy of molecules and more collisions per unit time. A general rule for most (not all) chemical reactions is that the rate at which the reaction proceeds will approximately double for each 10°C increase in temperature. Once the temperature reaches a certain point, some of the chemical species may be altered (e.g., denaturing of proteins) and the chemical reaction will slow or stop. In this case, the experiments were carried out at room temperature (approximately 22°C). However, I was unable to accurately control the temperature of the environment.
Medium:
The rate of a chemical reaction depends on the medium in which the reaction occurs. It may make a difference whether a medium is aqueous or organic; polar or non-polar; or liquid, solid, or gaseous. In this case the medium is liquid and aqueous.
Presence of Catalysts and Competitors:
Catalysts
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