Prediction
I predict that as temperature increases the rate of reaction will also increase. I think this is because the particles will have more energy and more collisions will occur.
Scientific Knowledge
Components affecting rates of reaction are temperature, whether a catalyst is used, the surface area, and concentration of acids. The higher the temperature the quicker the rate of reaction will be and vice versa.
Temperature is the factor I will be investigating for this experiment for my coursework. When the temperature is higher, the molecules move around quicker and they collide more often, this is called the collision theory. By investigating temperature I will increase the rate of energy that the molecules have, by increasing the temperature the molecules will move around faster, this is called the kinetic theory.
This is a diagram to show collisions at 30˚c.
The red molecules are sodium thiosulphate and the blue molecules are hydrochloric acid. The yellow is a collision between a blue and red molecule.
This is a diagram to show
Collisions at 60˚c.
Equipment list
2m-hydrochloric acids,
0.05m sodium thiosulphate,
Water bath, (electrical)
Conical flask x1 250cm3,
Thermometer,
Piece of paper with an X on it,
Stopwatch,
20cm3 measuring cylinder,
Safety goggles,
Diagram
Stopwatch
← Conical flask
← Solution containing
-> 5cm3 hydrochloric acid
Paper with x on it and 50 cm3 sodium thiosuphate
Safety
- Hydrochloric acid is corrosive; all spills must be reported and cleaned up immediately.
- Sodium thiosuphate (L) is contained in a dark glass bottle to prevent light breaking the bonds.
- Safety goggles must be worn at all times.
- Must be careful with hot water bath.
Preliminary work
This experiment was first of all carried out and demonstrated by our teacher during a lesson one morning. We were shown what happened when the two liquids were simply poured into a beaker together. Once added to each other the two liquids started to change and within a time there was evidence that a chemical reaction had occurred, because a cloudy, opaque precipitate formed. Heat energy was also given out. It is an exothermic reaction. A precipitate of sulphur is given off as a result of this reaction. This is the reason the liquid turns cloudy.
Method
- Set up equipment as shown in diagram above.
- Set the water bath at 10 ˚C
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Measure 5cm3of 2m-hydrochloric acid using a measuring cylinder.
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Measure out 50cm3 of 0.05m sodium thiosulphate into a clean conical flask and place into the water bath until it reached the required temperature.
- When the required temperature has been reached remove the conical flask from the bath and the hydrochloric acid. Place the conical flask on the cross and immediately start the stopwatch.
- Record the time it takes for the cross to disappear on the results table.
- Repeat steps 1-7 for each temperature, three times so that an average can be taken.
Fair testing
In order to make this experiment a fair test, the following dependant variables will be kept constant: -
- Same volumes of liquids will be used each time.
- The same concentrations of both the sodium thiosulphate and hydrochloric acid for the duration of the experiment.
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The same concentrations of both the sodium thiosulphate and hydrochloric acid for the duration of the experiment. The independent variable is temperature.
- Repeat the experiment 3 times to improve accuracy and validity my results.
- Clean equipment with water between each trial.
- Will carry out preliminary work to ensure that the practical works and that the concentrations selected are appropriate for the activity.