Rates of reaction part 1: measuring volume of gas produced
Investigate how changes in concentration affect the rates of reactions by measuring the volume of gas produced.
In this required practical, students will investigate the effect of concentration of an acid on the rate of a reaction. They will test two different concentrations of acid to see how quickly and how much gas is produced when it is reacted with a set length of Magnesium ribbon.
In the second part of the rates of reaction practical, students use a change in colour or turbidity to see how quickly Hydrochloric Acid reacts with Sodium Thiosulfate to give a cloudy solution.
Equipment (per participant)
• Safety goggles
• 100ml measuring cylinder x 2
• 100ml conical flask with bung and delivery tube
• Retort stand
• Water trough
• Stopwatch
• Hydrochloric Acid (1M & 1.5M)
• Magnesium ribbon
• CLEAPSS Hazcards: 47A, 59A
Method
- Students should collect the necessary equipment. Firstly, they measure 50mls of 1M Hydrochloric Acid and put this into the 100ml conical flask.
- Students must then add water to the trough so that it is two thirds full. They then need to fill the 100ml measuring cylinder with water and invert this, placing the opening of the cylinder underneath the water in the trough. This can be secured in a vertical position with a retort stand if necessary.
- The delivery tube should be positioned so that it is inside the underwater opening of the cylinder.
- A small piece of Magnesium ribbon should then be added to the acid in the flask, students then close the bung, and start timing with the stopwatch as soon as the flask is closed.
- They should choose a time interval (e.g., 10 seconds) and they must then read off the volume of gas in the inverted measuring cylinder each time the chosen time interval passes. The students must record their results in a suitable table.
- They must continue timing until the volume of gas does not change any more.
- They should then repeat the process using 50mls of 1.5M Hydrochloric Acid and then plot the results on a graph.
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Technician tips
• Always consult CLEAPSS guidance when diluting concentrated acids.
• To make 1M Hydrochloric Acid, 84mls of concentrated acid is slowly added to water in a fume cupboard and the solution is made up to 1L.
• To make 1.5M Hydrochloric Acid, 126mls of concentrated acid is slowly added to water in a fume cupboard and the solution is made up to 1L.
• Magnesium ribbon could be pre-cut into 3cm lengths to save time during the practical session.
To do this practical you will need
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