Unit 2 Flashcards
What is a homologous series?
A family of compounds with
same general formula
similar chemical properties
a trend in physical properties
Name 5 homologous series
Alkanes, Alkenes, cycloalkanes, alkanols and alkanoic acids
In a homologous series, what trend in physical properties is often seen?
Increasing number of carbon atoms leads to increasing melting and boiling points.
What is a hydrocarbon?
A compound containing only hydrogen and carbon atoms
Compare the chemical and physical properties of C6H14 and C12H26
Same homologous series so similar chemical properties. The C12H26 is likely to have higher melting and boiling points than C6H14. It will therefore be less flammable. The longer chain C12H26 will be more viscous (thick) and the shorter one C6H14 more runny.
What is saturated compound?
One containing only single carbon to carbon bonds.
What is an unsaturated compound?
A compound containing at least one carbon to carbon double bond.
How do you test for a double bond?
A compound with a double bond will rapidly decolourise bromine water.
What is the molecular formula of a compound?
Each element written with number of how many there are in the molecule.
What is the structural formula of a compound?
A formula showing all the covalent bonds as sticks.
What are isomers?
Molecules with the same molecular formulae but different structural formulae.
Do isomers have different physical properties?
Yes
Name a 6 carbon isomer of hexene in a different homologous
Cyclohexane
What are alkanes and what is their general formula?
Saturated hydrocarbons
general formula is CnH2n+2
What are cycloalkanes and what is their general formula?
Cyclic, saturated hydrocarbons
general formula is CnH2n
What are most alkanes used for?
Fuels
What are most cycloalkanes used for?
Fuels or solvents
What is a fuel?
Something you can burn to get energy
How are alkanes named?
Use the prefix to give the number of carbons.
use … ane at end to show it is saturated. Any branches are written at start with numbers to show which carbon they are on.
What are the prefixes for carbon chains 1 to 8
Meth = 1 eth = 2 prop = 3 but = 4 pent = 5 hex = 6 hept = 7 oct = 8
What is the name of an alkane containing three carbon atoms and no branches?
propane
What is the name of an alkane containing four carbon atoms and one branch?
methylbutane
Is there a chemical called 1-methylpropane?
NO. Branches can’t happen at the very end of a molecule. This substance would just be butane.
What are alkanes used for?
To make polymers(plastics) and alcohols.
What are alkenes and what is their general formula?
Unsaturated hydrocarbon containing the C=C double bond functional group. General formula is CnH2n
What is the name given to a reaction that gives out heat energy?
exothermic
Name the alkene with five carbon atoms and the double bond between the first and second carbon atoms.
pent-1-ene
What type of chemicals are in crude oil?
IT is a mixture of hydrocarbons-mainly alkanes.
What type of reactions do alkanes undergo?
Substitution reactions
What type of reactions do alkenes undergo?
Addition reactions
What happens to alkanes or alkenes as their carbon chain length increases?
Their boiling and melting points increase.
They become more viscous (thicker).
They become less flammable.
List three addition reactions that alkenes can undergo.
- Addition of hydrogen to make alkanes = hydrgenation.
- addition of halogens to make dihaloalkanes
- addition of water to make alkanols = hydration
What are saturated straight chain alcohols called and what is their general formula?
Alkanols
general formula CnH2n+1OH
What are alchohols used for?
Used as fuels - burn with clean flame or solvents
What is the name o the alcohol/alkanol with two carbon atoms?
Ethanol
Do alcohols dissolve in water?
Methanol, ethanol and propanol do but solubility deceases with increasing carbon chain length.
Why do alcohols decrease in solubility as the length of the carbon chain increases?
The hydrophobic hydrocarbon chain has increasing length and increasing overall effect.
What is vinegar?
CH3COOH
it is a solution of ethanoic acid
What are carboxylic acids?
Give their general formula.
Substances with the carboxyl functional group (-COOH)
general formula is CnH2n+1COOH
What are carboxylic acids used for?
Perservatives (eg pickling in vinegar)
Making soaps
Making medicines
Cleaning products
Do carboxylic acids dissolve in water?
methanoic acid, ethanoic acid, propanoic acid and butanoic acid do dissolve in water. BIgger molecules become increasingly insoluble.
What is the carboxylic/alkanoic acid with 4 carbon atoms called?
Butanoic acid
What pH do carboxylic acids have?
less than 7
List 4 substances that will react with carboxylic acids to make salts.
metals
metal oxides
metal hydroxides
metal carbonates
What salt is made when each of the following reacts with sodium hydroxide?
1) methanol acid
2) ethanoic acid
3) propanoic acid
1) sodium methanoate
2) sodium ethanoate
3) sodium propanoate
Which hydrocarbons are soluble in water?
None of them.
What is the name given to a reaction that takes in heat energy?
Endothermic
What is combustion?
When a substance burns and it combines with oxygen releasing heat energy.
What products are made when a hydrogen burns with lot of oxygen?
carbon dioxide and water
How do you measure how much energy a fuel can give out?
Burn a known mass of it and measure the temperature increase of a fixed volume of water.
Then use E=mcΔT to calculate the energy given out.
E = mcΔT
in the formula above what do each of the letters/symbols stand for?
E = energy given out m = mass of water heated c = specific heat capacity of water ΔT = change in temperature
Why are alcohols good fuels?
They are highly flammable and burn with very clean flames.
What is incomplete combustion?
When there s not enough oxygen so carbon (soot) and carbon monoxide are made instead of carbon dioxide.
What is a hydroxyl group and which homologous series has them?
-OH
found in alkanols/alcohols
What is a carboxyl group and which homologous has them?
-COOH
found in alkanoic acids/carboxylic acids
What would you call an alkanol with three carbon atoms?
propan-1-ol or propan-2-ol depending on were the -OH group is.
What type of reaction is the decolouristation of bromine water
addition
When bromine reacts with an alkene where do bromine atoms go?
One to each side of where the double bond was.
How can you make an alcohol?
React an alkene with water.
How can you seperate a mixture of compounds with different boiling points.
Distillation.
