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The determining of a rate equation from the reaction of sodium thiosulphate with hydrochloric acid - page 3
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: 3 of 8 pages: 1 2 3 4 5 6 7 8lower the activation energy of a chemical reaction and increase the rate of a chemical reaction without being consumed in the process. Catalysts work by increasing the frequency of collisions between reactants, altering the orientation of reactants so that more collisions are effective, reducing intramolecular bonding within reactant molecules, or donating electron density to the reactants. The presence of a catalyst helps a reaction to proceed more quickly to equilibrium. Aside from catalysts, other chemical species can affect a reaction. The quantity of hydrogen ions (the pH of aqueous solutions) can alter a reaction rate. Other chemical species may compete for a reactant or alter orientation, bonding, electron density, etc., thereby decreasing the rate of a reaction. In this case, no catalysts were present and I was very careful to both wash out and dry the flask after every use, so that subsequent reactions would not be contaminated with the products from previous ones.
Independent Variable
The concentrations of the reagents, sodium thiosulphate and hydrochloric acid.
Dependent variable
The time taken for the ‘X’, drawn on the tile I placed beneath the reacting flask, to disappear.
Safety Considerations:
• Take care when using hydrochloric acid, as it is corrosive and an irritant. Wash any splashes or affected areas of skin with copious amounts of water. Wear goggles during setting up and whilst doing the experiments to prevent hydrochloric acid getting into the eyes
• Sulphurous fumes produced in this reaction may be toxic by inhalation. Students who suffer from asthma need to take care.
• Take care when handling glassware to prevent breakages and injury
• At the end of the experiment, small quantities of the chemicals can be diluted with running water and run to waste
Apparatus
Safety goggles
3 x 50 ml burettes
2 x 100ml flasks
Stopwatch
A tile with an ‘X’ drawn on it
Glass stirring rod
0.4M sodium thiosulphate solution
2.0M hydrochloric acid
Distilled water
Method
Varying the concentration of sodium thiosulphate:
1. Set up three burettes in stands for hydrochloric acid, sodium thiosulphate and distilled water.
2. Add 5 cm3 of the hydrochloric acid solution to a 100 cm3 flask labelled X.
3. In a separate flask (Y) place 40 cm3 of the sodium thiosulphate solution. Note: No water is added at the moment but for the other reactions water will be added at this point
4. Mark
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