Rates of reaction
Hydrochloric acid and marble (CaCO3) react to form carbon dioxide gas. The gas can be
captured and measured using a gas syringe. A position sensor can be attached to the
syringe to record the rate of the reaction. This experiment shows the effect of surface
area on the reaction. The effect of acid concentration could also be explored.
What you need
Clamps, bosses and stands, marble pieces (large, medium and small sizes), 1M hydrochloric
acid HCl, flask, bung, delivery tube, a good gas syringe, interface, position sensor.
Setting up
Set up the flask, position sensor, the gas syringe and 1g of large marble pieces as
shown.
Connect the sensor to the interface. When you start your sensing software it should
recognise the sensor - otherwise you will have to do this yourself.
You may want to calibrate the sensor so that the computer displays the volume of the
syringe directly. If so, find the calibration feature in the software and enter the
volumes for the upper and lower limits of the position sensor movement - like a two-point
calibration.
Set up the software to record for 90 seconds. Start recording and immediately add 5cm3
acid to the marble in the flask.
Repeat using different sized marble pieces.
Questions
How does the graph show the progress of the reaction?
When was the reaction at its fastest? How can you tell?
Which part of each graph best shows how fast the reaction was working?
Calculate the average gradient of each of your graphs to compare them.
Teacher question
You may want to overlay, or merge together the results of several experiments. Were you
successful in doing this? Click here to respond.
This activity was adapted by Roger Frost
from The IT
in Science book of Data logging and Control. This page is � IT in Science. It may be
reproduced only for use within your school.
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