Experiment to find how different concentrations affect the rate of a chemical reaction

After doing the preliminary investigation I got the following results:

In my preliminary investigation I found that 10cm³ of HCL worked best with Na2S2O3 because there are not too much and not too little particles, therefore there’s a more likely chance of a collision and 10cm³ is an easy number to work with. I will use 10cm³ of HCL in my investigation.

To de-concentrate the solution I will add water to it. As I am using 50cm³ of Sodium Thiosulphate and 10cm³ of HCL I will need to take away 10cm³ from 50cm³ and add 10cm³ of water. This makes the solution 0.08molar instead of 0.1molar. I will continue de-concentrating the solution this way so I have 5 different concentrations: 0.1m, 0.08m, 0.06m, 0.04m and 0.02m.

Apparatus:

• Sodium Thiosulphate
• HCL
• Water
• Conical flask
• Marker (to place under conical flask-to measure the rate of reaction)
• A stop-clock
• Measuring cylinder

Diagram: 

Method:

1. Set up the apparatus as shown.
2. Measure out 50cm³ of 0.1molar Sodium Thiosulphate and put in the conical flask.
3. Add 10cm³ of 0.1molar HCL and start the stop-clock. Stop the clock when the x underneath the conical flask is no longer visible. Record the time it took for the solution to hide the x.
4. De-concentrate the solution so it becomes 0.08molar and do the same. Record the results.
5. Continue doing this until all 5 concentrations have been tested and the results have been recorded.
6. Repeat the experiment to find the average time for more accurate results and plot the results on a graph.

Prediction: 

I predict that the higher the concentration of Na2S2O3, the less time it will take to react because there are more particles for a collision to take place with HCL.

Hypothesis:

Increasing concentration increases the number of collisions. If the solution is more concentrated there are more particles of reactant between the water molecules, which makes collisions between the particles more likely.

Results: Expt

Results: Expt repeated

AVERAGE RESULTS:

Analysis:

Increasing concentration of a reactant means increasing the number of particles of that reactant in a given volume. I have found out that as you increase the concentration of a reactant, the rate of reaction also increases.