Aim: To decarbonate a bottle of soft drink and find out the amount of CO2 in the drink. * Principle: The reaction between carbon dioxide and water is an example of an equilibrium reaction:
* 3 soft drink bottles (300ml)
* 6g of salt (NaCl)
* Triple beam balance scale
* Digital scale
* Watch glass
* Electric hotplate
Standing up method
1. An unopened bottle of carbonated drink was weighted.
2. The cap was removed slowly with care, controlling the release of bubbles so that the soda water does not form out the top and lose soda water. 3. The opened bottle was left for 1 hour and reweighted. Warming method (uses the reduced water solubility of gas with temperature rise) 1. The open bottle stood carefully on an electric hotplate, and stirred using the thermometer to release the gas bubbles. 2. The soda bottle was heated to about 37oC.
3. The bottle and its cap were reweighted.
4. The change in weight was calculated due to loss of CO2 gas to the air. Salting method (uses the addition of ions which attract water molecules and reduce the availability of water able to dissolve gas) 1. 6g of salt was weighted.
2. The salt was added very slowly and carefully to the soda water so that the water does not degas too quickly. 3. The bottle and its cap were reweighted.
4. The change in weight was calculated due to loss of CO2 gas to the air, allowing the salt added to the soda water.
Method type | Weight before | Weight after | Change in weight (amount of CO2 loss) | Standing up| 338g| 337.5g| 0.5g|
Warming | 353.5g| 352.2g| 1.3g|
Salting | 338.2g| 342.6g| 1.5g|
* Calculate the loss of CO2 in (a) gram, (b) moles. (molar volume of a gas at 25oC and 101.3KPa pressure is 24.5L)
1. Compare the volume of gas released with the volume of liquid soda water...