Photo AI
The diagram shows the experimental set-up used by a group of students to prepare a sample of ethene from ethanol and to collect the ethene produced - Leaving Cert Chemistry - Question 2 - 2004
Question 2
The diagram shows the experimental set-up used by a group of students to prepare a sample of ethene from ethanol and to collect the ethene produced. (a) What is the... show full transcript
Worked Solution & Example Answer:The diagram shows the experimental set-up used by a group of students to prepare a sample of ethene from ethanol and to collect the ethene produced - Leaving Cert Chemistry - Question 2 - 2004
Step 1
What is the function of the glass wool? Identify the solid X and describe its appearance.
Answer
The glass wool serves to hold or soak up the ethanol at the end of the test tube, preventing it from wetting the aluminum oxide which is solid X. This ensures that the reaction occurs efficiently without interference from excess liquid.
Solid X, aluminum oxide (Al₂O₃), appears as a white powder, which may not show any other colors.
Step 2
State and explain two safety precautions which should be observed when carrying out the student experiment.
Answer
-
Keep gas away from flames: Ethene gas is flammable; hence, it is crucial to avoid any potential sources of ignition to prevent fire hazards. For instance, maintaining a clean workspace free from open flames is essential.
-
Use protective gloves: Operating with chemicals like potassium manganate(VII) requires wearing gloves to prevent skin contact, thus minimizing the risk of chemical burns or irritation.
Step 3
Step 4
If the ethene produced is bubbled through an acidified solution of potassium manganate(VII), the solution is decolourised showing that ethene is unsaturated. What is meant by the term unsaturated? Describe how you would carry out another test to confirm that ethene is unsaturated.
Answer
The term 'unsaturated' refers to organic compounds that contain at least one double or triple bond between carbon atoms. This characteristic allows them to react with additional atoms, such as hydrogen, in reactions like hydrogenation.
To carry out another test for unsaturation, one could add bromine water (a brown solution) to the ethene sample. If the solution decolourises, it indicates the presence of double bonds, confirming that ethene is unsaturated.
Step 5
Describe the flame that would be observed when a combustion test is carried out on a sample of ethene gas. Write a balanced equation for the combustion of ethene in excess oxygen.
Answer
When ethene undergoes combustion, a luminous and yellow flame is typically observed, which may also produce some smoky byproducts due to incomplete combustion.
The balanced equation for the complete combustion of ethene in excess oxygen can be written as: