Chemistry /Chemistry - Organic Families 1 Flashcards Part 3
What is the function of the glass wool in this experiment?
To soak up the ethanol and keeps it at one end of the test tube- stops ethanol from being directly heated.
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Key Terms
Term
Definition
What is the function of the glass wool in this experiment?
To soak up the ethanol and keeps it at one end of the test tube- stops ethanol from being directly heated.
State and explain three safety precautions in this experiment for ethene.
1. Ensure the test tube stopper on the test tube is airtight. 2. Ethene and ethanol are flammable- essential to keep them away from the Bunsen burner ...
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Why are the first few test tubes of gas collected discarded?
The first few test tubes consist mostly of displaced air and ethanol gas.
What is the ending for alkynes?
yne
Are alkynes saturated or unsaturated compounds?
Alkynes are unsaturated compounds containing one triple bond between two of the carbons.
Give an application of ethyne.
Ethyne gas is used in welding and cutting metals.
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| Term | Definition |
|---|---|
What is the function of the glass wool in this experiment? | To soak up the ethanol and keeps it at one end of the test tube- stops ethanol from being directly heated. |
State and explain three safety precautions in this experiment for ethene. | 1. Ensure the test tube stopper on the test tube is airtight. 2. Ethene and ethanol are flammable- essential to keep them away from the Bunsen burner flame to prevent a fire. 3. Wear gloves and use tongs; glass wool is irritant to skin- avoid touching. 4. Raise the apparatus from the water before turning the Bunsen burner off to avoid suck back of water up delivery tube-cold water being sucked back in the hot test tube could cause it to shatter. |
Why are the first few test tubes of gas collected discarded? | The first few test tubes consist mostly of displaced air and ethanol gas. |
What is the ending for alkynes? | yne |
Are alkynes saturated or unsaturated compounds? | Alkynes are unsaturated compounds containing one triple bond between two of the carbons. |
Give an application of ethyne. | Ethyne gas is used in welding and cutting metals. |
Describe the procedure to prepare ethyne. | Calcium carbide is placed in a reaction flask using a spatula, the dropping funnel is set above filled with water. The water is slowly added from the dropping funnel. Fizzing will occur in the reaction flask as ethyne is produced. The ethyne gas produced is passed through acidified copper sulfate to remove impurities. The pure ethyne gas is collected over water. |
Write a balanced equation to prepare ethyne. | CaC2 + 2H2O -> Ca(OH)2 + C2H2; calcium carbide + water -> calcium hydroxide + C2H2. |
Describe the physical properties of ethyne. | Ethyne is a colourless gas with a sweet smell. It's insoluble in water but dissolves in non-polar substances e.g., cyclohexane. |
Describe the combustion of ethyne and name its positive result for its test. | Ethyne burns with a very bright, very smoky yellow flame, with a lot of soot formed as a result of unburned carbon. Limewater turns milky white proving carbon dioxide was formed in the combustion. |
Compare the flame observed when observing ethyne and ethene. | The flame observed when burning ethyne is brighter and smokier than when burning ethene. |
How does the flame used in oxyacetylene welding, where ethyne is burned in air in a combustion test? | Ethyne will burn in pure oxygen with a hotter, cleaner flame with less smoke/soot. |
Write a balanced equation for the complete combustion of ethyne. | C2H2 + 2 1/2 O2 -> 2CO2 + H2O. |
What do ALL organic compounds produce when combusted completely? | Carbon dioxide and water vapour. |
Describe the test for unsaturation in ethyne using bromine water and its result. | Procedure- add red bromine water to a test tube of ethyne gas stopper and shake, result, red bromine water turns colourless - ethyne is unsaturated. |
Testing for unsaturation using acidified potassium manganate VII on ethyne and its result. | Add to a tube of ethyne, stopper and shake purple potassium manganate VII turns colourless- ethyne is unsaturated. |
Outline 2 safety precautions in production of ethyne. | Ethyne is explosive with air- keep any naked flame away from the apparatus. Use spatula to place calcium dicarbide into flask- it's an irritant to skin. |
Give three observations in the reaction flask as the reaction proceeds. | Fizzing is observed. A white substance formed. The reaction flask gets hot. |
Describe the appearance of calcium carbide. | Calcium carbide is a grey-black solid. |
Explain why fizzing occurs in the reaction flask. | Ethyne gas is produced. |
Explain the white substance that formed in the flask as the reaction proceeds. | The white substance formed as a result of the production of calcium hydroxide Ca(OH)2. |
Explain why the flask gets warm as the reaction proceeds. | The reaction between calcium carbide and water is exothermic (gives out heat). |
Why must the products of the reaction be passed through acidified copper sulfate? | The ethyne formed is not pure, passing it through acidified copper sulfate removes impurities. |
Name three impurities that could be present in the ethyne gas produced that are removed by the acidified copper sulfate. | Hydrogen sulfide, phosphine, ammonia. |
Why are the first few test tubes of gas collected and discarded? | They contain mostly of displaced air and not ethyne gas. |