Prediction:
I predict that as the concentration of Sodium Thiosulphate decreases, the rate of reaction will slow down as well.
Na S O + HCl NaCl + S + SO + H O
Sodium Thiosulphate + Hydrochloric Acid Sodium Chloride + Sulphur Dioxide +Water
Apparatus/Chemicals
Conical Flask Sodium Thiosulphate
White paper with a cross Hydrochloric Acid
2 measuring cylinders Distilled water
Stop clock
Safety Goggles
Safety Precautions
Hydrochloric Acid is corrosive therefore I’ll be using gloves to protect my hand¸ goggles to protect my eyes, and a lab cloth to protect my clothes.
Method
We laid out the apparatus with the beaker on the piece of paper with a cross on it. 5cm of water of HCl (Hydrochloric Acid) and 40cm of Sodium Thiosulphate which varied concentration from 40ml to 5ml are poured into two measuring cylinders and then poured into a conical flask which is placed on top of the piece of paper marked with the letter X. The stopwatch will now be started. We will wait until we cannot see the concentration and see the cross.
Diagram to show set up:
Look down at cross from above
Results Table ( to show how the results will be taken down)
Analysis
I feel that my results are good. All of the results fitted the line of best fit perfectly and no anomalies were found in the graphs. The experiment was repeated 3 times to ensure that I had not made any mistakes. This proves that my prediction is right. I said that as the concentration decreases, the rate of reaction slows down.
Conclusion
I conclude that the more concentrated a reactant is, the quicker the rate of reaction time will be.
I have come to this conclusion because of several reasons. Firstly, my results give conclusive evidence that as the amount of Sodium Thiosulphate decreases, and the amount of water in the solution increases there are less atoms to collide and therefore less successful collisions causing chemical change so the reaction rate is slower. In a more concentrated solution, there are more atoms to collide so the reaction time is quicker.
Evaluation
My experiment went according to plan I had no problems doing it. I believe there is always going to be a human error factor involved when you are measuring liquids and looking for an end point in the reaction.Although the reaction that was done had a fairly definite end point it was still hard to tell whether the whole cross had disappeared or not. Even though these human errors did occur I still feel that the experiment on a whole was fair I feel that my results are very accurate and have a certain amount of consistency between them it wouldn’t be necessary to repeat them again.