Equipment Needed
Measuring Cylinder: 10cm3
50cm3
100cm3
Conical Flask 250cm3
Beakers
Safety Goggles
Stop Clock
Step-by-Step Guide
- Measure 50cm3 of Sodium Thiosulphate into a conical flask.
- Place the flask onto a cross drawn onto a piece of paper.
- Add 5cm3 of Hydrochloric Acid to the flask using a small measuring cylinder and stir the solution and immediately start the clock when acid is added.
- Look through the solution until the cross cannot be seen and stop the clock, write down results onto a table.
- Repeat 6 more times using:
1. Sodium Thiosulphate 45cm3 Water 5cm3 Hydrochloric Acid 5cm3
2. Sodium Thiosulphate 40cm3 Water 10cm3 Hydrochloric Acid 5cm3
3. Sodium Thiosulphate 35cm3 Water 15cm3 Hydrochloric Acid 5cm3
4. Sodium Thiosulphate 30cm3 Water 20cm3 Hydrochloric Acid 5cm3
5. Sodium Thiosulphate 25cm3 Water 25cm3 Hydrochloric Acid 5cm3
6. Sodium Thiosulphate 20cm3 Water 30cm3 Hydrochloric Acid 5cm3
Prediction
I predict that the greater amount of Sodium Thiosulphate the faster the chemical reaction will happen.
I think that the concentration of the solution will affect the rate of reaction because the rate of reaction depends on how frequently the molecules in the reacting substances collide. Because there are more molecules about, the frequency of successful collisions is greater, and the reactions happen faster.
Fair Test
I will be trying to make this a fair test by trying to use the exact amount of the solution I need to use. I would use the same beaker every time. I could use the same cross on each experiment with by using the same colour.
What Happened
The solution gradually turned opaque because sulphur was made.
Results
Averages
50 = 43.96
45 = 48.823
40 = 58.043
35 = 66.567
30 = 75.916
25 = 91.853
20 = 99.756
Conclusion
The more concentrated the solution was with Sodium Thiosulphate the quicker the reaction was.
I came to this conclusion because my evidence shows that as the amount of Sodium Thiosulphate increase and the amount of water decreases, the reaction got quicker.
My results on my graph went in a negative correlation.
Explaining
Theses results because the higher the amount of Sodium Thiosulphate and the lower amount of water, the more successful collisions of atoms inside the solution there were.
Comments
I feel my results were quite accurate.
My results came out in a negative correlation on a line graph.
My only suspicions were that on the 1st and 2nd results, the gap between 50 Sodium Thiosulphate and 20 Sodium Thiosulphate was quite large (78seconds and 59seconds) but on the second the solutions seemed to work quicker than the other two sets of results (41seconds).
Improvements
I think, if I had did my work quicker, my results would have been most perfect.
If I used the same cross on each paper it might have been fairer as tone of colour might have been slightly different.