We are going to investigate the reaction between Sodium Thiosulphate and Hydrochloric Acid. We are also going to investigate the rate of reaction and what changes affect this as well as the reaction itself. Scientific Knowledge:- There is a theory that states that certain factors, properties and states of the different chemicals used in the reaction affect the rate of reaction, which is in effect, how fast or slow the reaction occurs. These factors are: 1. Surface area of the two chemicals 2. The concentration of the chemicals
3. Stirring the contents of the conical flask while the reaction is taking place 4. The temperature of the chemicals involved in the reaction This theory is called the collision theory, because as it goes, if there is a significant difference between the chemicals, whether it be more or less, the faster the reaction is said to take place. This is due to the particles that make up the two separate chemicals being made to move that extra bit faster than normal, as one or more of these factors is applicable.
Although there are four factors to vary, we will only deal with one at a time, and as we go on we will try to get on to another of these factors if at all possible. Prediction:- As we will be investigating the reaction between Sodium Thiosulphate and Hydrochloric Acid when stirred at different times, I will now predict what I expect to occur in the reaction. First of all, with stirring the mixture, the obvious assertion to make is that stirring will increase the speed of the reaction, or cause it to occur faster than without any outside interference.
Whether I am right or not and if my prediction proves right or not will be discovered later. Method:- We took a plain piece of paper and drew a cross or a letter ‘X’ on it. Then we placed a conical flask directly over the top of the ‘X’ so that it was visible through the bottom of the flask when viewed from above it. Then we took a measuring cylinder, and measured the same amount of Hydrochloric Acid and Sodium Thiosulphate. After we had checked that both chemicals were the same amount, we put them both into the conical flask and started our stopwatch.
We then measured the time taken for the reaction to take place; that is, when we lost visibility of the ‘X’ we stopped our stopwatch and recorded the results. We also did each test twice, and used the stirring factor to influence the reaction. Naveen Chauhan. 10Sc2:- Page 2 Apparatus- Stirring implement (a) Conical flask (b) Hydrochloric Acid (c) Sodium Thiosulphate (c) Sheet of paper Pencil Results:- Number of times stirred every __ seconds Attempt No. 0 10 7 5 2 Continuously Attempt No. 1 (mins) 9 Naveen Chauhan. 10Sc2:- Page 3 Graph:- Naveen Chauhan.
For safety in the laboratory we took the following precautions and measures: a) Goggles were used throughout the practical, and we made sure they were always worn when each investigation was carried out to ensure we were following laboratory safety rules and regulations. b) We were also careful when measuring out the chemicals. This was especially important as any spilled matter in a laboratory is not safe and is a safety hazard.
c) If by any chance there was any matter spilled, we were careful to clean up the mess so as not to present a hazard. Those were the specific safety measures we undertook during this practical investigation. Fair Test:- To ensure that this investigation we carried out was fair, we carried out the practical bearing in mind certain measures and factors, that could make the whole practical void and strip it of any equity it had. First of all we carefully and precisely measured out the two particular chemicals that we were dealing with. This same volume was used for every test that we carried out.
Also the piece of paper with the mark on it was kept the same every time to ensure it was fair. The conical flask was also kept the same, but we washed it out thoroughly after each individual test carried out. This was to guarantee that there was as little chemicals left over from the last test as possible. This would lead to an imbalance in the volumes of certain chemicals, which would ultimately have meant inaccurate results. Also when stirring was carried out we used the same stirring implement as this would be fair on all the tests we did.
We also carried out each test twice in order to ‘double check’ our results as well as to achieve an average value for each test. This would help us to weigh up the results better. These aforementioned measures were those that we took to ensure our practical was carried out to highest possible degree of equity.
These were attained to best of our ability and the practical was, in our opinion valid. Average times for results of test:- Stirred after how many seconds Attempt 5 Conclusion:- The Hydrochloric Acid and Sodium Thiosulphate were meant to react fastest when they were stirred continuously rather than once every few seconds. My prediction however was wrong and the chemicals reacted fastest when these stirring conditions applied, that is stirring every few seconds. This is because the more you stir it the more you disturb the chemicals and prevent them from reacting.
So when the lower stirring conditions applied thsat is when the reaction was the fastest. Evaluation:- In the end practical was fair and equal for all tests that we carried out and we worked well as well as more importantly safely. Not only regarding our own safety but also of the safety of those around us, working at the same time. This also helped us to achieve accurate as well as reliable results for our practical investigation. We did not get on to the other factors such as: 1. Surface area of the two chemicals 2. The concentration of the chemicals.
3. The temperature of the chemicals involved in the reaction My prediction turned out to be wrong as the chemicals reacted much faster when they were stirred after a little while rather than continuously. Our experiment was fair for the reasons stated before. It was also safe for the reasons given in the ‘Safety’ section. Show preview only The above preview is unformatted text This student written piece of work is one of many that can be found in our GCSE Patterns of Behaviour section.