A student prepared and collected ethene (C₂H₄) gas using the arrangement of apparatus and chemicals shown below - Leaving Cert Chemistry - Question 1 - 2018
Question 1
A student prepared and collected ethene (C₂H₄) gas using the arrangement of apparatus and chemicals shown below. A few stopped test-tubes of the gas were kept to exa... show full transcript
Worked Solution & Example Answer:A student prepared and collected ethene (C₂H₄) gas using the arrangement of apparatus and chemicals shown below - Leaving Cert Chemistry - Question 1 - 2018
Step 1
Identify the white solid A
96%
114 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The white solid A is identified as aluminium oxide (Al₂O₃).
Step 2
Describe the appearance of the gas collected
99%
104 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The appearance of the gas collected is colourless, indicating that it is likely pure ethene.
Step 3
Explain why the first test-tubes of gas collected are not used
96%
101 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The first few test-tubes of gas collected are often not used because they may contain impurities or displaced air from the system, which can affect experimental results.
Step 4
What is suck-back?
98%
120 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Suck-back occurs when a liquid is drawn back into the apparatus due to a sudden change in pressure, creating a vacuum that pulls the liquid backwards.
Step 5
Why is suck-back hazardous?
97%
117 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Suck-back can be hazardous as it may draw harmful liquids or materials back into the reaction vessel or apparatus, leading to contamination or chemical accidents.
Step 6
What precaution should be taken to avoid suck-back?
97%
121 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
To avoid suck-back, the test-tube should be equipped with a proper vacuum trap or a one-way valve to prevent backflow of liquids into the apparatus.
Step 7
Identify a reagent used to test ethene for unsaturation
96%
114 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
A commonly used reagent for testing ethene for unsaturation is bromine water (Br₂ solution).
Step 8
What colour change is a positive result in this test using the reagent you identified?
99%
104 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The positive result for unsaturation is indicated by the bromine water changing from red/orange to colourless, confirming the presence of double bonds in ethene.
Step 9
How was the combustion test carried out?
96%
101 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The combustion test was carried out by igniting the test-tube containing ethene gas. A lit splint was then held at the mouth of the tube to observe the reaction.
Step 10
Describe the flame observed
98%
120 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The flame observed was bright yellow, luminous, fairly clean, and not very sooty (smoky), indicating complete combustion.
Step 11
Copy, complete, and balance the equation for the complete combustion of ethene in oxygen
97%
117 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
C₂H₄ + 3O₂ → 2CO₂ + 2H₂O
Join the Leaving Cert students using SimpleStudy...
