Key Variables
We could use temperatures of the acid or the Thiosulphate and use different temperatures, however, this is way too fiddly and will takes ages to get right.
Instead we are going to change the concentration. We have decided to use the concentration of the acid.
Fair Test
We will change the concentration of the Acid using water to dilute it. We are keeping the total amounts of Thiosulphate and acid the same but we will also keep the same cross for every experiment.
Method
We are going to fill 50cm3 of Sodium Thiosulplate into a beaker and do this five times. Then we are going to put in different levels of Hydrochloric Acid into a measuring beaker (10cm3 of acid and 40cm3 of water, etc) up to 50cm3. We will draw a cross and place a beaker on top. Then we place the two solutions together and time how long it takes for the cross to disappear. We do this five times for each diluted solution.
(Stuff needed: Beaker, Paper the cross, measuring cylinder, Na2S2O3, HCl)
Safety
We are going to use goggles to make sure we are safe if anything happens. If we get any HCl on our hands, we will wash them as soon as possible.
Preliminary Experiment
After doing the whole experiment once using diluted Acid, we found that the difference between figures was too small. So we have decided to switch the roles of the acid and the Thiosulphate (Dilute the Thiosulphate).
Actual Experiment
Aim
We are studying the rate of reaction between Hydrochloric acid and Sodium Thiosulphate. We are going to change the concentration of the Hydrochloric acid.
Theory
The Collision theory is when particles store up enough activation energy, they collide and react with each other
Hydrochloric Acid + Sodium Thiosulphate → Sulphur + Sulphur Dioxide
+ Sodium Chloride + Water
2HCl + Na2S2O3 → S + SO2 + 2NaCl + H2O
The factors that could affect the rate of reaction are:
- Temperature
- Concentration
- Catalysts
- Surface area
Temperature affects the reaction by changing the speed of the reaction depending on the temperature of the Thiosulphate. If it is hot, then the reaction is quicker than if it was cold.
Concentration affects the reaction depending on how concentrated the reaction is. If it is highly concentrated, the reaction is quicker than if it was not highly concentrated.
Catalysts speed up reactions if they are compatible and surface area affects differently in different situations. If it is large it reacts quickly and if smaller it reacts slower.
Prediction
Because of concentration, we can vary the times between the separate experiments. The particles that are in the water dilute those in Sodium Thiosulphate effecting its molar value. If affects the activation energy time.
Key Variables
We could use temperatures of the acid or the Thiosulphate and use different temperatures, however, this is way too fiddly and will takes ages to get right.
Instead we are going to change the concentration. But the concentration of the acid produces little change, so the Thiosulphate will be used instead.
Fair Test
We will change the concentration of the Thiosulphate using water to dilute it. We are keeping the total amounts of Thiosulphate and acid the same but we will also keep the same cross for every experiment.
Method
We are going to fill 50cm3 of Hydrochloric Acid into a beaker and do this five times. Then we are going to put in different levels of Sodium Thiosulplate into a measuring beaker (10cm3 of acid and 40cm3 of water, etc) up to 50cm3. We will draw a cross and place a beaker on top. Then we place the two solutions together and time how long it takes for the cross to disappear. We do this five times for each diluted solution.
(Stuff needed: Beaker, Paper the cross, measuring cylinder, Na2S2O3, HCl)
Safety
We are going to use goggles to make sure we are safe if anything happens. If we get any HCl on our hands, we will wash them as soon as possible.
Results Table
EXPERIMENT 1
EXPERIMENT 2
EXPERIMENT 3
AVERAGES
(GRAPH OF ANALYSIS ON SEPARATE SHEET)
Conclusion
We have found out that the higher the concentration, the slower the acid takes to react with the Thiosulphate solution. Meaning that the less diluted the Thiosulphate is, the faster reaction time will be produced when mixed with the Acid.
Analysis
If I were to do this experiment again, Instead of using a cross, I would use a light sensor to give a more accurate reading. This is because the cross method depends on one person’s sight and analysis of weither the cross is gone or not. Light sensors will change their value until it stops, when the reaction is over. The reaction may still be going on, even when the person tells the timer that the reaction is finished.