Safety
Before conducting the experiment we must make a few safety precautions, for our own health and safety. Being careful and aware will prevent accidents from happening. Here are a few things we must make sure we do: Wear goggles to protect the eyes. Avoid spilling the acid onto your skin as it is corrosive. If it gets in contact with skin was thoroughly with water and seek medical assistance if necessary.
Apparatus
- Gas syringe
- Retort stand
- Magnesium
- Stopwatch
- 0.5, 1, 1.5, 2 and 2.5m of hydrochloric acid
- Measuring cylinder
- Thermometer
Rubber pipe
TEST TUBE
GAS SYRINGE
RETORT STAND
Method
- Set up the equipment as shown above.
- Use the same procedure for each molar of hydrochloric acid.
- Obtain a strip of magnesium which will already be cut to the same length and size.
- Then measure out 20cm3 of hydrochloric acid using a measuring cylinder.
- Pour the hydrochloric acid into a test tube, as shown above and then add the magnesium strip and attach the test tube to the gas syringe immediately.
- Using the stopwatch record the amount of hydrogen produced in the gas syringe every 10 seconds and on each occasion continue measuring for 180 seconds. The hydrogen produced each 10 seconds is gathered in the gas syringe and the volume measured.
Predictions
My prediction is that the most concentrated hydrochloric acid will produce the most hydrogen and the weakest strength of hydrochloric acid will produce the least amount of hydrogen. As the higher the strength of hydrochloric acid the faster the particles will move and collide with other particles the faster this is done the more hydrogen there will be. The reaction time will be much faster with the strongest acid and the hydrogen will produced at a greater rate.
COLLISION THEORY: MORE COLLISIONS INCREASE THE RATE OF REACTION
Temperature
By increasing the temperature the amount of energy produced will increase, due to the amount of energy the particles will have, this will cause them to collide harder and faster increasing the number of successful collisions e.g. increasing temperature increases particle movement.
Concentration
The concentration will affect the rate of reaction if the concentration is increased the number of reactants increase i.e. there are more hydrogen and chlorine molecules. This increase in concentration will also increase reactivity.
The experiment was carried out using the equipment and method as above and the following results were recorded:-
Table of results
As you can see 0.5 molar of hydrochloric acid is the weakest and doesn’t produce much hydrogen, while 2.0 molar produces the most hydrogen.
This is because the 2.0 molar of hydrochloric acid has a much higher concentration than the 0.5 molar so this means there will be more particles moving more quickly and colliding much more and a lot faster.
Table of results when temperature was varied
I again carried out the experiment but changed the temperature, the concentration of acid remained constant at 1.5 molar .
As you can see the higher the temperature the more hydrogen there is being produced.
A graph for the results when changing the concentration of acid
The line graph clearly shows reactivity is directly linked to concentration.
Conclusion
After carrying out the experiment and investigating how concentration and temperature affects the rate of reaction. I’ve found out that the less concentrated the acid you use the slower the rate of reaction. The more concentrated the acid the faster the rate of reaction.
Similarly as temperature is increased reactivity increases.
The results show that the volume of hydrogen produced is greatest when the concentration of the acid increased. The experiment has produced slightly irregular results in that 2.0 molar produced a greater a volume of hydrogen than 2.5 molar.
This may attributed to human error or inaccuracies in the equipment as the difference in the gas is very small.
EVALUATION:
The difficulties I encountered were -
- Ensuring the magnesium was exactly the same size.
- Measuring the volume of hydrogen produced every 10 seconds proved difficult due to the apparatus in use i.e. the gas syringe’s markings.
- Human error in that the results could not be accurately recorded exactly every 10 seconds.
- The seals on the apparatus may not have been air tight and a small amount of hydrogen may have escaped.