Complete combustion:
any fuel + O2 --> CO2 + H2O
Balance the C, then H then Os.
Incomplete combustion
any fuel + O2 --> CO + H2O
Reaction of CO2 with limewater:
Ca(OH)2 + CO2 --> CaCO3 + H2O
-------> in excess CO2 if you keep bubbling CO2 through: CaCO3 + CO2 + H2O --> Ca(HCO3)2
Fermentation:
C6H12O6 --> C2H5OH + CO2
Production of CO2 in lab:
CaCO3 + HCl --> CaCl2 + CO2 + H2O
Thursday, August 19, 2010
Question 1 Combustion
Ethane and ethanol are organic compounds used as fuel.
Ethane burns with an orange flame and some soot forms.
Ethanol burns with an almost invisible flame with no soot forming.
By considering the products of these reactions, predict and justify which fuel will have the larger impact on people.
Include examples of how people would be affected, and an appropriate balanced equation for each fuel.
Ethane burns with incomplete combustion forming carbon monoxide and water. During this reaction soot is also formed.
The equation for this reaction is:
CH3CH3 + 3.5O2 --> 2CO + 3H2O
This fuel would have a greater impact on people because it produces soot, which leads to pollution and respiratory problems and CO which is a toxic gas because it can bind to the red blood cells better than oxygen preventing oxygen from getting around the body. This leads to asphyxiation.
Ethanol burns with complete combustion forming carbon dioxide and water.
The equation for this reaction is:
C2H5OH + 3O2 --> 2CO2 + 3H2O
This fuel would have a lesser impact on people because the products it produces do not have a direct impact in human health.
The CO2 produced does increase the greenhouse effect, which is the trapping of heat energy from the sun in the Earths atmoshpere causing temperatures to increase. This leads to changes in weather patterns and the melting of the polar ice caps. This leads to water levels increasing which will affect the enviroment in which humans live.
Question 2 Fermentation
Beer is brewed by placing sugar, hops and brewer’s yeast into a fermentation tank. The final product contains alcohol and bubbles of carbon dioxide.
Discuss with reference to the properties of carbon dioxide, how this simple process makes a carbonated (fizzy) drink
• An equation for the fermentation of the sugar is the brewer’s yeast.
• An explanation of the observations regarding the fizziness in terms of the properties of carbon dioxide.
• The tests you could carry out to identify the gas as carbon dioxide and the observation you would make carbon dioxide gas.
Fermentation is the process by which glucose is converted into ethanol and carbon dioxide. This process occurs in a fermentation vat. The brewers yeast is the catalyst for this reaction.
C6H12O6 --> 2C2H5OH + 2CO2
Because the CO2 prduced is a colourless gas which is slightly soluble in water and more dense that air, the carbon dioxide dissolves in the beer. When the cap is removed from the bottle some of the CO2 gas escapes causing the beer to fizz. This is caused by the change in pressure caused when the bottle is opened.
Question 3 Allotropes
Discuss why graphite can be used as an electrode in batteries
It may be useful to include a diagram showing the structure of graphite.
Include in your answer:
• What physical property of graphite allows it to be an electrode?
• A description of the structure of the shape and bonding in graphite.
• What is it about the structure that allows it to be an electrode?
Graphite can conduct electricity because it has free electrons between the graphite layers. This is because its structure consists of layers of C atoms that are each covalently bonded to 3 other C atoms. This leaves on of Carbons valence electrons free to move and carry electrical charge.
Question 4 Polymers
Polythene (polyethene) is a polymer that has many industrial and household uses ranging from buckets to plastic bags
(a) Name the monomer that polythene is produced from?
(b) Draw a short section of the polythene chain showing at least three repeating units.
A) ethene (CH2=CH2)
B) .......CH2-CH2-CH2-CH2.......
Question 5 fractional dist illation
Discuss how crude oil can be separated into its components using fractional distillation.
In your answer, outline what crude oil is and refer to the physical properties of hydrocarbons.
Crude oil is made up of hydrocarbons of differing chain lengths. Because the boiling point of hydrocarbons depends on chain length, the longer the chain the higher the boiling point, these hydrocarbons are able to be separated according to boiling point using a process called fractional distillation.
Question 6 Products of combustion
Discuss how you could conduct an experiment to prove that the products of complete combustion are carbon dioxde and water.
The products of complete combustion are carbon dioxide gas and water. By burning fuel and passing the gases produced through a tube in a beaker of ice water the water vapour produced in the reaction will condense on the side of the tube. This can be confirmed as water by using cobolt chloride paper which turns from pink to blue in the presence of water.
When the gases of the reaction are passed through a test tube containing limewater, the lime water will turn cloudy indicating the presence of carbon dioxide, This is because the carbon dioxide gas reacts with the limewater producing calcium carbonate which is insoluble
Ca(OH)2 + CO2 --> CaCO3 + H2O
limewater insoluble white ppt
Ethane and ethanol are organic compounds used as fuel.
Ethane burns with an orange flame and some soot forms.
Ethanol burns with an almost invisible flame with no soot forming.
By considering the products of these reactions, predict and justify which fuel will have the larger impact on people.
Include examples of how people would be affected, and an appropriate balanced equation for each fuel.
Ethane burns with incomplete combustion forming carbon monoxide and water. During this reaction soot is also formed.
The equation for this reaction is:
CH3CH3 + 3.5O2 --> 2CO + 3H2O
This fuel would have a greater impact on people because it produces soot, which leads to pollution and respiratory problems and CO which is a toxic gas because it can bind to the red blood cells better than oxygen preventing oxygen from getting around the body. This leads to asphyxiation.
Ethanol burns with complete combustion forming carbon dioxide and water.
The equation for this reaction is:
C2H5OH + 3O2 --> 2CO2 + 3H2O
This fuel would have a lesser impact on people because the products it produces do not have a direct impact in human health.
The CO2 produced does increase the greenhouse effect, which is the trapping of heat energy from the sun in the Earths atmoshpere causing temperatures to increase. This leads to changes in weather patterns and the melting of the polar ice caps. This leads to water levels increasing which will affect the enviroment in which humans live.
Question 2 Fermentation
Beer is brewed by placing sugar, hops and brewer’s yeast into a fermentation tank. The final product contains alcohol and bubbles of carbon dioxide.
Discuss with reference to the properties of carbon dioxide, how this simple process makes a carbonated (fizzy) drink
• An equation for the fermentation of the sugar is the brewer’s yeast.
• An explanation of the observations regarding the fizziness in terms of the properties of carbon dioxide.
• The tests you could carry out to identify the gas as carbon dioxide and the observation you would make carbon dioxide gas.
Fermentation is the process by which glucose is converted into ethanol and carbon dioxide. This process occurs in a fermentation vat. The brewers yeast is the catalyst for this reaction.
C6H12O6 --> 2C2H5OH + 2CO2
Because the CO2 prduced is a colourless gas which is slightly soluble in water and more dense that air, the carbon dioxide dissolves in the beer. When the cap is removed from the bottle some of the CO2 gas escapes causing the beer to fizz. This is caused by the change in pressure caused when the bottle is opened.
Question 3 Allotropes
Discuss why graphite can be used as an electrode in batteries
It may be useful to include a diagram showing the structure of graphite.
Include in your answer:
• What physical property of graphite allows it to be an electrode?
• A description of the structure of the shape and bonding in graphite.
• What is it about the structure that allows it to be an electrode?
Graphite can conduct electricity because it has free electrons between the graphite layers. This is because its structure consists of layers of C atoms that are each covalently bonded to 3 other C atoms. This leaves on of Carbons valence electrons free to move and carry electrical charge.
Question 4 Polymers
Polythene (polyethene) is a polymer that has many industrial and household uses ranging from buckets to plastic bags
(a) Name the monomer that polythene is produced from?
(b) Draw a short section of the polythene chain showing at least three repeating units.
A) ethene (CH2=CH2)
B) .......CH2-CH2-CH2-CH2.......
Question 5 fractional dist illation
Discuss how crude oil can be separated into its components using fractional distillation.
In your answer, outline what crude oil is and refer to the physical properties of hydrocarbons.
Crude oil is made up of hydrocarbons of differing chain lengths. Because the boiling point of hydrocarbons depends on chain length, the longer the chain the higher the boiling point, these hydrocarbons are able to be separated according to boiling point using a process called fractional distillation.
Question 6 Products of combustion
Discuss how you could conduct an experiment to prove that the products of complete combustion are carbon dioxde and water.
The products of complete combustion are carbon dioxide gas and water. By burning fuel and passing the gases produced through a tube in a beaker of ice water the water vapour produced in the reaction will condense on the side of the tube. This can be confirmed as water by using cobolt chloride paper which turns from pink to blue in the presence of water.
When the gases of the reaction are passed through a test tube containing limewater, the lime water will turn cloudy indicating the presence of carbon dioxide, This is because the carbon dioxide gas reacts with the limewater producing calcium carbonate which is insoluble
Ca(OH)2 + CO2 --> CaCO3 + H2O
limewater insoluble white ppt
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