Nature's chemistry- unit 2
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- Created by: chloeellis98
- Created on: 04-09-18 18:57
what is a homologous series?
a family of hydrocarbons with similar chemical properties who share the same general formula
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what is the general formula of alkanes?
CnH2n+2
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Alkanes have many uses, can you name some?
methane- (natural gas) used in cooking ; propane- used in gas cylinders for BBQ's ; octane- used in petrol for cars
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what is the name and formula of the first 8 alkanes?
methane- CH4 ; ethane- C2H6 ; propane- C3H8; butane- C4H10; pentane- C5H12; hexane- C6H14; heptane- C7H16; octane- C8H18
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what are the general rules you should remember when naming organic compunds?
1. The longest unbranched chain containing the functional group is the parent molecule 2. The position of the functional group should be indicated with a number, numbering from the end nearest the functional group 3. Name and no. the branches
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what is the general formula for the alkenes?
CnH2n
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Alkenes are unsaturated. What does "unsaturated" mean?
This means that they have a carbon to carbon double bond. Alkanes are labelled "saturated" as they only have single bonds.
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what is the test for an unsaturated hydrocarbon?
it decolourises bromine water quickly. Saturated hydrocarbons do this slowly so a distinction can be made.
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what can alkenes be used for?
fuels, solvents and starting materials for everyday products such as plastics and alcohol
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when naming an alkene, what differs from an alkane?
For an alkene you must identify the postion of the double bond
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what is the general formula of the cycloalkanes?
CnH2n (same as alkene however without a double bond)
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if the cycloalkanes dont have a double bond will they decolourise bromine water rapidly?
No, as they have single carbon to carbon bonds. They are isomers of alkenes.
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How are cycloalkanes used?
in motor fuel, natural gas, kerosene, diesel and other heavy oils
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what are isomers?
isomers are compounds with the same molecular formulae( same number of each type of atom) but a different structural formulae
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If a hydrocarbon reacts with oxygen in a combustion reaction, what will the two products be?
Hydrocarbon +oxygen = carbon dioxide + water
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what is the test for the presence of carbon dioxide gas?
carbon dioxide gas turns limewater from colourless to milky white.
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If water is produced in a combustion reaction, it will condense and can be indicated by what?
it will turn cobalt chloride paper from blue to pink
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what could incomplete combustion( an insufficient supply of oxygen) lead to?
toxic carbon monoxide being produced instead of carbon dioxide
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Why are alkenes more reactive than alkanes and cycloalkanes?
because they have a double bond
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what group are the only ones capable of undergoing an addition reaction?
Alkenes only can undergo addition reactions due to the double bond. Alkanes, alkenes and cycloalkanes can undergo combustion reactions with O2 however.
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Give an example of an addition reaction with ethene and bromine( i.e the test for alkenes with bromine water)
Ethene + Bromine = 1,2-dibromoethane ( the 2 bromine molecules add across the double bond, breaking it and attaching to the two carbon molecules- creating an alkane from an alkene)
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The addition of bromine to an alkene is called?
Bromination
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The additon of hydrogen to an alkene is called?
Hydrogenation (requires a nickel catalyst)
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The additon of water to an alkene is called?
Hydration (requires a phosphoric(v) acid catalyst) alkene + water = Alcohol
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what is the functional group for the alcohols( also known as alkanols)?
hydroxyl functional group (OH)
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what is the general formula for the alcohols?
CnH2n+1OH
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what are alcohols used for?
ethanol is used in alcoholic drinks, many other alcohols exist as fuels or solvents. propan-2-ol is used in hand sanitiser
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are small alcohols like methanol, ethanol miscible in water?
yes, the larger the alcohol the less miscible in water
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why do the melting and boiling point of alcohols increase with size?
because of the strong intermolecular forces
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carboxylic acids (also known as alkanoic acids) have what functional group?
carboxyl functional group -COOH
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what is the general formula for the carboxylic acids?
CnH2n+1COOH
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are the smallest carboxylic acids miscible in water?
yes, the larger the carboxylic acid the lower the miscibility
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why do the melting and boiling points of carboxylic acids increase with size?
due to the strong intermolecular forces
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what are carboxylic acids used for?
vinegar- ethanoic acid, this can be used in chemicals to treat limescale and also to preserve food
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what pH do carboxylic acids have and what do they form?
a pH of less than 7 and form salts on neutralisation with a base
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what salt will this reaction make? sodium hydroxide and ethanoic acid
sodium ethanoate and water
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what salt will this reaction make? lithium carbonate and propanoic acid
lithium propanoate and carbon dioxide and water
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what salt will this reaction make? magnesium and methanoic acid
magnesium methanoate and hydrogen
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what happens when fuels such as alkanes and alcohols burn?
they release heat and light energy to the surroundings in exothermic reactions
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what do endothermic reactions do?
take in heat energy
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what are these reactions known as?( exothermic and endothermic)
combustion reactions
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what is the word equations for propane gas burning in a plentiful supply of oxygen?
propane + oxygen = carbon dioxide + water
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what would the balanced formulae equation be for this?
C3H8 + 5O2 = 3CO2 + 4H2O
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what hydrocarbons can undergo combustion?
alkanes, alkenes and cycloalkanes
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what is the word equation for hydrocarbons burning in a plentiful supply of oxygen?
hydrocarbon + oxygen= carbon dioxide + water
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what is the test for the presence of carbon dioxide?
it turns limewater from clear to milky white
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what is the test for water produced from a combustion reaction?
it turns cobalt chloride paper from blue to pink
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what could incomplete combusiton( insufficient supply of oxygen) lead to?
toxic carbon monoxide being produced instead of carbon dioxide
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how is enthalpy (energy released) calculated?
through this equation; Eh=cm∆T
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what is "c" in the equation?
the specific heat capacity of water= 4.18KJ
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what is "m" in the equation?
the mass of water in Kg (100cm3= 0.1kg)
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what is "∆T" in the equation?
change in temperature from initial temp-final temp
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Other cards in this set
Card 2
Front
what is the general formula of alkanes?
Back
CnH2n+2
Card 3
Front
Alkanes have many uses, can you name some?
Back
Card 4
Front
what is the name and formula of the first 8 alkanes?
Back
Card 5
Front
what are the general rules you should remember when naming organic compunds?
Back
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