These are the apparatus that I have used
- A large beaker
- Conical flask
- Large measuring cylinder for thiosulphate only
- Paper with an X
- Small beaker
- Small measuring cylinder for hydrochloric acid only
- Stop watch
- Hydrochloric acid
- Thiosulphate
- Distilled water
To conduct my experiment safely I will follow normal laboratory rules. These are the safety issues, which are need to take into consideration
- The wearing of safety goggles to protect my eyes from chemical splashes
- Make sure coats and bags are out of the way as you could trip and have an injury
- Long hair should be tied back so they do not make contact with any chemicals
- Standing up for the experiment therefore this reduces the risk of tripping and spilling chemicals
- Taking care of chemicals especially hydrochloric acid and thiosulpahte as they are both irritants
Method
At first I collected all my apparatus which were a large beaker, a conical flask, a large measuring cylinder, paper with an X, small beaker, small measuring cylinder, top watch, hydrochloric acid, thiosulphate concentration and distilled water. Initially at first I put 200cm3 of thiosulphate solution into a large beaker and by sing a large measuring cylinder I poured 50cm3 into the cylinder and put it in the conical flask, I left this large measuring cylinder for the thiosulphate solution only. I then drew an X on a piece of paper and placed my conical flask on the X. I then put 30cm3 of hydrochloric acid into a small beaker and from a small measuring cylinder I measured 10cm3 I kept this measuring cylinder for the hydrochloric acid only. Subsequently I poured the 10cm3 of hydrochloric acid in to the conical flask, which already had thiosulphate solution init and swirled it, at the same time I also started my stopwatch. I observed how the X vanished and recorded the time. As the solution as the thiosulphate solution has now been diluted so next I took 40cm3 of thiosulphate solution, 10cm3 of distilled water and 10cm3 of hydrochloric acid and repeated the method. I repeated this till 10cm3 of thiosulphate solution. I repeated it each twice to make it a fair test and also to give me reliable test.
From my experiment I feel I have covered a suitable range from 50cm3 to 10cm3 of thiosulphate and my results table clearly reflects that. To make it a fair test I have also repeated it each twice.
Conclusion
I conclude that the more concentrated a reactant is the quicker the rate of the reaction time. I have came to this conclusion because firstly my results table clearly reflects this point, that the stronger the concentration the faster the reaction, this in scientific terms is because as there less atoms t collide and therefore less collisions causing chemical change so the reaction rate is slower, but on the other hand in a more concentrated solution there are more atoms to collide so the reaction time is quicker.
My results support my prediction because I said ‘the greater the concentration of sodium thiosulphate t the faster the chemical reaction so the cross will disappear quickly’ I believe that I was correct as my results reinforce this fact and also and I have also got a secondary course which states that the reaction time will be faster with a concentrated solution because the more molecules there are the frequency of successful collisions is greater and therefore the reaction rate is speeded up.
In the 1st experiment where there was 50cm3 of thiosulphate and 10cm3 of hydrochloric acid the reaction time was faster because as there was a more concentrated soloution in the same volume there was a greater chance of the hydrochloric acid and thiosulphate colliding and reacting.
Thiosulphate
Hydrochloric Acid
In my last experiment which was when the the thiosulphate was 10cm3 and was diluted, and hydricloric acid 10cm3, there were less particles of the thiosulphate to collide with the acid so the reaction time was extensive.
Thiosulphate
Hydrochloric Acid
My experiment was successful and managed to complete the experiment fully and fairly. The fastest reaction was with no water, 60cm3 of thiosulphate solution and 10cm3 of hydrochloric acid. This reaction was the fastest one with 43secs an average of 45. The slowest reaction was with 10cm3 of thiosulphate, 10cm3 of distilled water and 10cm3 of hydrochloric acid which took 1minute and 19 seconds an average of 1.18. The experiments were handled fairly but I think there is also a human error factor involved when you are measuring liquids and observing reactions, although through out my experiment I tried my level best to observe it was still fairly hard to be definite if the cross had disappeared or not. So this could be improved by instead of using the eyes to see if the sulphur had disappeared you could use a device such as a light sensor, this would pass though the flask, of where an where the reaction is taking place to a receiver and when the light sensor can not reach the receiver the timing would be stopped automatically.
Although my experiment went to plan there were still flaws in it. For example I only obtained two sets of results and then worked out an average, to improve this I could do the test maybe 3 to 4 times to give a more reliable average. There was particular result that was not really an anomaly, it still followed the pattern but was still different to the other results, which I got when I did it for a second time. This was when the thiosulphate was 20cm3 in the first test I got 1 minute and 58 seconds and to in my second test I got 1 minute and 2 seconds, I think that this a human error which is the reason of doing more tests.
