Worksheet for Video #3 - Oxidation of an Alcohol using a Catalyst
Complete this page after viewing the video and performing the investigation.
- Why was the stopper removed when the test tube of methanol was placed in the water bath?
- Why was the platinum heated at a safe distance away from the water bath?
- What are the reactants and products of this reaction when the platinum glows bright red?
- What other product is possible if the oxygen supply is limited? Why should this reaction be only conducted in a well-ventilated area like in a fume hood?
- What is the role of platinum in this reaction?
- Methanol is one of the most volatile organic solvents found in a typical high school laboratory. Why is the high volatility of methanol a fire safety hazard? How can this risk be minimized?
Answers for Oxidation of an Alcohol using a Catalyst
Complete this page after viewing the video and performing the investigation.
- Why was the stopper removed when the test tube of methanol was placed in the water bath?
The thermal energy of the water bath readily vaporizes methanol. This would result in an increase of gas pressure if the test tube was sealed. This increase in pressure could eject the stopper or break the test tube.
- Why was the platinum heated at a safe distance away from the water bath?
Methanol is a very flammable liquid. Consequently, the platinum strip should be heated a few metres away from the methanol to avoid accidental ignition of methanol vapour.
- What are the reactants and products of this reaction when the platinum glows bright red?
The reactants are methanol and oxygen. The products are carbon dioxide and water and represent the complete combustion of methanol.
- What other product is possible if the oxygen supply is limited? Why should this reaction be only conducted in a well-ventilated area like in a fume hood?
When the oxygen supply is limited, methanal (formaldehyde) may also be produced. Since formaldehyde is toxic, the demonstration should only be conducted in a well-ventilated area to limit the inhalation of formaldehyde vapours.
- What is the role of platinum in this reaction?
Platinum is a catalyst in this reaction and without platinum the reaction is too slow.
When oxygen is not limiting the energy released by the complete combustion of methanol causes the platinum to glow red. When oxygen is limiting, incomplete combustion occurs, and the energy released will not cause platinum to heat to red hot.
- Methanol is one of the most volatile organic solvents found in a typical high school laboratory. Why is the high volatility of methanol a fire safety hazard? How can this risk be minimized?
Since methanol is so volatile, it quickly evaporates into a highly flammable vapour. The fire hazard of methanol vapour can be minimized by ensuring the methanol stock bottle is not brought into the lab, keeping the quantities of methanol used to a minimum and conducting the demonstration in a well ventilated area away from open flames or devices that could generate an electric spark or discharge.