Finally, we will make sure that the same person judges when the cross is no longer visible or the reaction times result could not be accurate, as 2 people could have different eyesight and therefore different opinions on when the x has disappeared.
Prediction I predict that as I decrease the concentration of the hydrochloric acid, the reaction rate will get slower.
Also, we need to wash the beakers and cylinders before using them as there could be another chemical left in the bottom.
This could start off unwanted reactions and affect the reaction rate.
Explanation Of Prediction I think that 25cm3 acid and 25cm3 thio will react faster than any of the solutions with a lower concentration of acid because there are more acid particles in the solution, which means more particle collisions, resulting in a faster reaction.
If the solution is diluted, there aren't as many acid particles to collide with the thio particles and so the reaction is much slower.We then added the contents of the cylinder to the conical flask along with the 25cm3 sodium thiosulphate.Variables I changed the concentration of the hydrochloric acid by adding water to it.25 Acid / 0 Water / 25 thio20 Acid / 5 Water / 25 thio15 Acid / 10 Water / 25 thio10 Acid / 15 Water / 25 thio5 Acid / 20 Water / 25 thio Instead of changing the concentration of the acid, we could have added water to the thio, like this:25 Acid / 25 thio / 0 Water25 Acid / 20 thio / 5 Water25 Acid / 15 thio / 10 Water25 Acid / 10 thio / 15 Water25 Acid / 5 thio / 20 Water We could also have changed the temperature of the thio before mixing it with the hydrochloric acid, or the temperature of the hydrochloric acid before mixing it with the thio.Also to ensure a fair test I will use the same beakers and measuring cylinders each time for holding the thio and the acid.This is because if I put the thio into a beaker that had previously held acid then it could start off a reaction and affect the overall reaction rate.I will make sure that my experiment is fair by using a different measuring tube and pipette for each chemical. I think that the rate of reaction between sodium thiosulphate and hydrochloric acid will increase as the concentration of the sodium thiosulphate solution increases.I state this because by increasing the concentration you’re also increasing the amount of particles in the solution.I am going to investigate how the concentration of the acid effects the speed of the reaction.Apparatus1 small measuring cylinder1 large measuring cylinder1 small beaker1 large beaker Hydrochloric Acid Sodium Thiosulphate Cross drawn on paper Conical flask Water Stopclock Method First of all we measured out 25cm3 acid and 25cm3 sodium thiosulphate.Results/mins Acid/cm3Water/cm3Reaction Time 1Reaction Time 2Average Reaction Time2501.522.332.122052.092.432.2615102.242.542.3910153.053.383.215204.585.555.26/secs Acid/cm3Water/cm3Reaction Time 1Reaction Time 2Average Reaction Time250112153132.520512916314615101441741591015185218201.5520298355326.5Analysis/Conclusion We discovered that 25cm3 hydrochloric acid and 25cm3 sodium thiosulphate solution had the fastest reaction rate, just as we had predicted.English: ions in solution of hydrochloric acid Français : ions en solution dans l'acide chlorhydrique by Wikipedia.