Both the sodium thiosulphate and the hydrochloric acid are soluble in water, so the concentration of either can be changed.
This is the method:
The first step is to stand up the conical flask on the cross, which is on the piece of paper.
Using a measuring cylinder pour in 50 cm of Sodium Thiosulphate solution. Carefully pour it in to the conical flask.
Measure 5cm of hydrochloric acid by using a measuring cylinder and then pour in the hydrochloric acid into the conical flask and then start the stop clock. When the ‘x’ is no longer visible stop the clock
Do this for the whole first part of the experiment.
Then repeat the entire procedure. Repeated results and averages will improve the finding. Repeating t he experiment will give us a good set of results. If one result is totally different to the set of results then a third experiment is carried out.
I predict that the more dilute the solution is the longer it will take to get cloudy. I think this will happen because the less sodium thoisulphte there is; the longer it will take for the hydrochloric acid to react. Because of my prediction I think that my graphs will be a negative correlation.
- This test tube has no water so this means it is easier for the reaction to take place.
- In this test tube there is some water so this delays the reaction from taking place.
- In this test tube there is a lot of water, this water blocks the sodium thiosulphate and the hydrochloric acid from reacting.
I will measure the time it takes for the sodium thiosulphate to react with the hydrochloric acid. I will also observe how long it will take for the sodium thiosulphate to turn milky. I will change the amount of sodium thiosulphate and water of the solution. The Hydrochloric acid will stay the same.
To make my experiment a fair test I will do the following:
- I will make sure that the measuring cylinders for the HCL and thiosulphate will not be mixed.
- I will wash out the cylinder at each interval
- I will use the same standard each time for judging when ‘x’ disappears
These three points will make my results a fair more reliable and keep mistakes to a minimum, it will also the whole investigation successful.
I will make ten measurements during this investigation. This includes the repeated experiment.
There are some safety rules like being careful when handling with the sodium thiosulphate and the hydrochloric acid this means wearing goggles which will protect your eyes.
RESULTS:
ANALYSIS:
In my results I have found that as the water increases, the time taken was longer for the milky solution to go cloudy. This means that when there is less Sodium Thiosulphate and more water it is harder for the reaction to take place, which means that the reaction is delayed. This increases the time for the solution to get milky.
My prediction was the following:
‘The more dilute the solution is the longer it will take to get cloudy’ this prediction is right.
EVALUATION
I am trying to find out the rate of reaction and the effect that different changes have on it. My method was good. I altered the amount of water and sodium thiosulphate in my experiment. I made it a fair test by using the same standard each time for judging when ‘x’ has disappeared. I made sure that the measuring cylinders for the HCL and thiosulphate were the same so that they do not get mixed up. I kept the Hydrochloric acid the same all the way through the experiment. I measured the time it took for the sodium Thiosulphate and Hydrochloric acid to react together.
I used measuring cylinder and a conical flask. I think washing and drying the flask thoroughly through each interval could have improved the experiment.
