Experimental Design of Rates of Reactions

This experiment aims to identify the rates of reactions for variables with respect to change in temperature and surface area. The prediction is that an increase in temperature will lead to an increase in the chemical reaction, while a reduced chemical reaction is predicted when the surface area is increased. The experiment involves using sodium thiosulfate solution and antacid tablets to measure the reaction time. The results show that the chemical reaction takes place much faster when the surface area is small.

TITLE: experimental design of rates of reactions
Aim
The aim of the experiments identifies the rates of reactions for variables with respect to change
in temperature and surface area.
Specific objectives
To identify the change on chemical reaction with change in temperature1
To identify the change on chemical reaction with change on surface area or size of an antacid
tablet
Prediction
The prediction of the first is experiment is that increase in temperature will lead to an increase on
the chemical reaction2. In the second experiment a reduced chemical reaction is predicted when
the surface area is increased3. This is simply because there is an increased area where the
chemical reaction is expected to take place as compared to a reduced surface area or size.
Materials
Part A
Thermometer (-10 °C to 110 °C)
400 cm3 beaker (for use as a water bath)
Plastic container with lid
2 glass tubes to hold 12-14 cm3 of liquid
0.05 mol dm–3 (or 40 g dm–3) sodium thiosulfate solution
1.0 mol dm–3 hydrochloric acid (or 0.5 mol dm-3 sulfuric acid)
Measuring cylinder
1 Nicolas. Vogel, Surface Patterning with Colloidal Monolayers. (Dordrecht: Springer, 2013). 78
2 Vijay K, Thakur, and Singha Amar S. Surface Modification of Biopolymers. (Hoboken, New Jersey: Wiley,
2015). 445
3 Dave J, Adams, Dyson, Paul J. and Tavener Stewart J.. Chemistry in Alternative Reaction Media. (Chichester,
West Sussex, England: J. Wiley, 2004). 56

Plastic graduated pipette
Stopwatch
Part B
Effervescent antacid tablets (at least four)
Sheet of paper
Spoon
Four clear 12-ounce (or larger) drinking glasses
Measuring cup
Teaspoon
Tap water
Stopwatch
Pen
Method
Part A
1. Using a measuring cylinder add 10.0 cm3 of 0.05 mol dm-3 of sodium thiosulfate solution
to the second tube. Measure the temperature of the sodium thiosulfate solution.
2. Write down the start temperature and add 1 cm3 of the acid to the thiosulfate solution and
start timing.
3. Record the reaction time by noting time taken form the cross to disappear from view.
4. Now record the temperature for the reaction mixture. Pour the cloudy contents of the vial
into the sodium carbonate solution (the ‘stop bath’).
5. Next add water from a very hot water tap to the plastic container. The water should be no
hotter than 55 oC. Note down the new temperature.
6. Now measure another 10.0 cm3 of 0.05 mol dm-3 sodium thiosulfate solution into a clean
tube.
7. Leave the reaction to take place in the hot bath for about 3 minutes.
8. Repeat steps 3 to 5 above.
9. Repeat the same procedure in order to obtain results for at least 5 different temperatures
in total.
Part B

1. In this experiment, take four antacid tablets. First set a single whole tablet aside and then
split another into halves, the third one into quarters and the fourth one crush into powder.
2. Take four glasses and fill them with tap water. Measure their temperature to make sure
their temperature is the same.
3. Take one glass full of water and place a whole antacid tablet.
4. Start a stopwatch once the tablet is inside.
5. Star with teaspoon until the whole tablet dissolves. This marks the end on the chemical
reaction
6. Stop the stopwatch and record the time taken for the tablet to dissolve.
7. Repeat step 2 to 6 for the half tablet, the quarter one and the powder tablet.
Results and observation
Tablet status Reaction time
1 Whole tablet 3.5 min
2 Half tablet 2 min
3 Quarter tablet 1 min
4 Powder tablet 30 sec
The surface area of the tablet is critical in the chemical reaction4. The powder tablet is able to
dissolve quicker than the whole tablet. This shows that the chemical reaction takes place much
faster when the surface area is small.
4 Robert, Gardner, and Kemer Eric. Easy Genius Science Projects with Temperature and Heat: Great
Experiments and Ideas. (Berkeley Heights, NJ: Enslow Publishers, 2009). 33

References
Adams, Dave J, Paul J. Dyson, and Stewart J. Tavener. Chemistry in Alternative Reaction Media.
(Chichester, West Sussex, England: J. Wiley, 2004).
Gardner, Robert, and Eric Kemer. Easy Genius Science Projects with Temperature and Heat:
Great Experiments and Ideas. (Berkeley Heights, NJ: Enslow Publishers, 2009).
Thakur, Vijay K, and Amar S. Singha. Surface Modification of Biopolymers. (Hoboken, New
Jersey: Wiley, 2015).
Vogel, Nicolas. Surface Patterning with Colloidal Monolayers. (Dordrecht: Springer, 2013).