mock revision Flashcards
what is an ionic bond?
an ionic bond is a strong electrostatic attraction between oppositely charged ions. they are formed between a metal and a non metal atom
what is the structure of an ionic bond and what are the patterns of behaviour?
ionic substances from giant ionic 3D lattices. they have high melting and boiling points. they tend to be soluble in water, crystalline and brittle. solid ionic substances do not conduct electricity, as the ions cannot freely move, but they are good conductors when they are molten in solution
what is a covalent bond?
a strong electrostatic attraction between two nuclei and a shared pair of electrons. a covalent bond is formed between two non-metal atoms
what is the structure of a covalent bond and what are the patterns of behaviour?
They can be simply molecules or giant structures. Simple covalent bonds don’t conduct electricity. Usually have high melting and boiling points.
what is a simple molecular substance?
Simple molecular structures have covalent bonds joining the atoms together, but intermolecular forces that act between neighbouring molecules are weak
what are the properties of a simple molecular substance?
simple molecular substances tend to be gases at room temperature (e.g. hydrogen, ammonia, methane) as they have low melting and boiling points. They don’t conduct electricity because the molecules don’t have a charge (they are neutral). the intermolecular forces between molecules are weak, but they get stronger with the size of the molecule.
what are the main allotropes of carbon?
diamond
what is an ionic bond?
an ionic bond is a strong electrostatic attraction between oppositely charged ions. Formed between a metal and a non metal.
how is an ionic substance structured?
ionic substances from giant ionic 3D lattices
what are the properties of ionic substances?
they have high melting and boiling points. they tend to be soluble in water, crystalline and brittle. solid ionic substances do not conduct electricity, as the ions cannot freely move, but they are good conductors when they are molten in solution.
what is a covalent bond?
a covalent bond is a strong electrostatic attraction between two nuclei and a shared pair of electrons. formed between non-metal atoms
what is the structure of covalent substances?
they can be simple molecules or giant structures.
what are the properties of covalent substances?
simple covalent bonds don’t conduct electricity
what is a simple molecular substance?
Simple molecular structures have covalent bonds joining the atoms together, but intermolecular forces that act between neighbouring molecules are weak
what are the properties of simple molecular substances?
simple molecular substances tend to be gases at room temperature (e.g. hydrogen, ammonia, methane), as they have low melting and boiling points. they don’t conduct electricity because the molecules don’t have a charge (they are neutral)
what are the main allotropes of carbon?
diamond, graphite, buckminsterfullerene, graphene
what is the structure of diamond?
giant covalent. each carbon atom forms 4 covalent bonds.
what are the properties of diamond?
very high melting and boiling points because the strong covalent bonds are difficult to break. it is an insulator because particles have no freedom to move. they are very strong and hard.
what is the structure of graphite?
giant covalent. each carbon atom forms 3 covalent bonds
what are the properties of graphite?
very high melting and boiling points because the strong covalent bonds are difficult to break. it is a conductor because it has delocalised electrons that can carry charge through the structure.
what is the structure of buckminsterfullerene?
simple molecular. each carbon forms 3 covalent bonds
what are the properties of buckminsterfullerene?
not very high melting and boiling points because you only need to overcome relatively weak forces between molecules (no covalent bonds broken). It is an insulator because although it has delocalised electrons, they cannot move from one molecule to another. soft and brittle.
what is the structure of graphene?
giant covalent. each carbon atom forms 3 covalent bonds.
what are the properties of graphene?
very high melting and boiling points because the strong covalent bonds are difficult to break. it is a conductor because it has delocalised electrons that can carry charge through the structure. very strong
what is an allotrope?
An allotrope is one or more forms of a chemical element that can exist in the same physical state. Allotropes have different chemical and physical properties due to the different ways in which the atoms bond together to create each allotrope.
what is metallic bonding?
metallic bonding is the strong electrostatic attraction between closely packed positive metal ions and a ‘sea’ of delocalised. formed between metal atoms
what are the properties of a metallic substance?
contain electrons that are free to move in the metal structure, carrying charge from place to place and allowing metals to conduct electricity. high melting and boiling points. free electrons allow metal atoms to slide over each other, so metals are malleable and ductile.
what is an alloy?
a mixture of a metal and another element, usually another metal or carbon. alloys have properties that are different to the metals they are made of. they are harder.
why are alloys harder?
alloys contain atoms of different sizes, which distorts the regular arrangements of atoms. This makes it more difficult for the layers to slide over each other, so alloys are harder than the pure metal.
how does reactivity change as you go down group 7?
as you go down group 7, reactivity increases. the distance to the nucleus increases - the atoms of each element get larger going down the group as we keep adding shells of electrons. this means that the outer shell gets further away from the nucleus and is shielded by more internal electron shells. the further the outer shell is from the positive attraction of the nucleus, the easier it is to remove the electron.
what are the appearances of the main halogens?
fluorine: pale yellow gas at room temp
chlorine: pale green gas at room temp
bromine: brown liquid at room temp (orange when gas)
iodine: grey solid at room temp
aluminium: grey solid at room temp
what names are given to horizontal rows and vertical columns in the periodic table?
row = period
columns = groups
what happens to the electronic configuration as you go down a group?
it increases by one shell
how is the modern periodic table arranged?
in order of number of protons
what happens in a reaction between chlorine and sodium bromide?
2NaBr (aq) + Cl2 (aq) –> 2NaCl (aq) + Br2 (aq)
The solution turns brown which is the displaced bromine in the solution. The Cl displaces the Br because chlorine is more reactive than bromine.
what happens in a reaction between bromine and sodium chloride?
COME BACK TO THESE
what is an isotope?
an isotope is an atom of an element with different numbers of neutrons but the same number of protons
how do you calculate the relative atomic mass?
weighted average mass of all the isotopes of an element relative to their abundance
RAM = (percentage of isotope A x mass of isotope A) + (percentage of isotope B x mass of isotope B) / 100
how do you calculate RFM
sum of all the RAMs of all the atoms in a formula (this is just the mass listed on the periodic table)
what is the value of one mole?
1 mole is equivalent to avigadro’s number. Avigadro’s number = 6.02 x 10^23
how do you calculate the number of moles in a substance
moles = mass/RFM
what is molecular formula?
molecular formula tells us the actual number of atoms of each element in a molecule
what is empirical formula?
empirical formula is the simplest whole number ration of elements in a compound
how do you calculate empirical formula?
Work out the moles of each element in the compound. Divide the moles by the smallest in moles. This gives you the empirical formula.
Example:
Find the empirical formula of a compound which contains 0.08g of hydrogen and 0.64g of oxygen.
Mr of hydrogen = 1
Mr of oxygen = 16
Moles of hydrogen = 0.08
Moles of oxygen = 0.04
Divide moles by 0.04…
Empirical formula = H2O
how to calculate molecular formula?
Find the empirical formula.
Calculate the mass of the empirical formula (e.g. if the empirical formula is CH2, the RFM of that will be 14)
Use the RFM of the entire compound to find the molecular formula by division
how to calculate percentage yield?
percentage yield = actual amount/theoretical amount (x100)
why does yield not get to 100%
- Reaction is incomplete/does not go to completion
- Possibility of unwanted side reactions (formation of bi-products)
- Product transfer losses
what is a hydrocarbon?
a substance made of carbon and hydrogen only
what is a saturated hydrocarbon?
a hydrocarbon that contains only single bonds
what is the functional group?
an atom or group of atoms that give a molecule its chemical properties. For example, in the alcohols series, the functional group is the -O-H group.
What is a homologous series?
A series (a ‘family’) of organic compounds with similar chemical properties because they have the same functional group. Each member differs from the next by a constant unit.
What is the general formula for an alkane?
C(n)H(2n+2)
what is an isomer?
compounds with the same molecular formula but with different structural formulae (different arrangement of atoms in space)
how do you name an isomer?
Find the longest change - will end in ane
Branch name will end in -yl
If there is more than one branch, we give the position of each. Eg.
C-C-C-C-C = pentane
C-C-C-C
l = 2-methyl butane
C
1 carbon = meth-
2 carbons = eth-
3 carbons = prop-
4 carbons = but-
5 carbons = pent-
6 carbons = hex-
7 carbons = hept-
8 carbons = oct-
9 carbons = non-
10 carbons = dec-
what is cracking?
process to trn long chain alkanes that we have little use for into shorter chain alkanes and alkanes that have more uses and are in higher demand
what are the potential uses of alkanes?
short chain alkanes –> fuels
alkenes –> to make plastics
what is an alkene?
like an alkane but there is a double bond between two carbons (saturated hydrocarbons)
what is an addition reaction?
when small molecules can be added across the double bond to make saturated compounds
what is bromination?
C2H4 + Br2 –> C2H4Br2
The double bond between the carbons is removed and the two bromine ions join the compound (like an alkane but instead of two of the hydrogens its two bromines)
What is hydrogenation?
C2H4 + H2 –(150 degrees + catalyst)–> C2H6
The alkene becomes an alkene when the double bond between the carbons is broken.
What is hydration?
C2H4 + H-OH –(300 degrees + phosphoric acid)–> CH3CH2OH
The OH replaces one of the hydrogens in an alkane. The double bond in the alkene is broken.
What happens when bromine reacts with an alkane?
SUBSTITUTION REACTION (happens under UV light)
One bromide ion replaces one of the hydrogens and the displaced hydrogen bonds with the other displaced bromine.
What happens when bromine reacts with an alkene?
ADDITION REACTION (bromination)
Creates an alkane but not quite because instead of two of the hydrogens there’s two bromide ions.
what are the products of complete combustion?
CO2 + H2O
what are the products of incomplete combustion?
(CO + C) + H2O
l
one, the other or a mix of the two
what happens when you add bromine water to an alkene?
the solution goes from orange to colourless
what are polymers?
very long molecules
covalent bonds within chains
chains not necessarily chemically bonded
LONG CHAIN MOLECULE MADE FROM LOTS OF SMALL MOLECULES JOINED TOGETHER
what is a monomer?
small molecules that join together to make polymers
what are the environmental issues with addition polymers?
at the end of life of plastic, either it is incinerated to produce energy and causes the emission of toxic gases, or it goes to landfill and takes up valuable land
monomers are derived from finite resources (crude oil)
The resulting polymer is saturated and therefore unreactive.
Product is hard to break down, lasts hundreds of years.
If a chloride is present when incinerated they emit HCl or Cl2, which is toxic
What is attracted to the cathode?
Cations are attracted to the cathode which is also known as the negative electrode
What is attracted to the anode?
Anions are attracted to the anode which is also known as the positive electrode
What is electrolysis?
spitting compounds using electricity
Describe the electrolysis of lead bromide. Include the half equations.
Anode: oxidation
2Br- –> Br2 + 2e-
Products: bromine as a brown liquid/orange gas
Cathode: reduction
Pb2+ + 2e- –> Pb
Products: lead as a pellet/lump of silvery metal
Does reduction take place in the anode or the cathode?
Reduction takes place at the cathode.
Does oxidation take place in the anode or the cathode?
Oxidation takes place at the anode.
How does reactivity differ between atoms and ions?
The more reactive as an atom, the less reactive as an ion.
How do you know what takes priority at the cathode during electrolysis in water/solution?
If metal above H in the reactivity series then H get electrolysed. If metal below H in the reactivity series then metal+ is electrolysed. (copper, silver, gold)
How do you know what takes priority at the anode during electrolysis in water/solution?
If a halogen is present (F-, Cl-, Br-, I-) it gets electrolysed. If a halogen is not present then OH- gets electrolysed.
What is the half equation for the electrolysis of OH-?
4OH- –> O2 + 2H2O + 4e-
What is the half equation for the electrolysis of H+?
2H+ + 2e- –> H2
What are the products of a reaction between an acid and a metal?
salt + hydrogen
What are the products of a reaction between an acid and a base?
salt + water
What are the products of a reaction between an acid and a carbonate?
salt + water + carbon dioxide
Describe a titration…
Attach a pipette filler carefully to a glass pipette, draw the air out. Draw up liquid to beyond the 25cm^3 line
Slowly release the liquid until the bottom of the miniscus just touches the line.
Transfer to the vonivsl glsdk snf sff 2-3 drops of indicator.
Run the sodium hydroxide into the acid quickly until ________cm^3. Then add the solution drop by drop, swirling the conical flask over the white tile at the same time.
When the indicator turns from colourless to pink.
Add these to the results table. Subtract the initial burette reading from the final burette reading to get your titre.
What is the solute?
The substance that gets dissolved.
What is the solvent?
The substance that does the dissolving.
What is the definition for ‘dissolve’?
When the solute is broken down by the solvent
What is the definition of ‘soluble’?
A substance that can be dissolved.
What is the definition of a ‘solution’?
A mixture of a dissolved solute in a solvent
What is the definition of a ‘saturated solution’?
Solution in which no more solute can dissolve in the solvent.
What is the definition of ‘solubility’?
Measure of how much of a solute can dissolve in a certain amount of solvent (usually water). It is measured in grams per 100g of water.
What is the equation for concentration? (mol/dm^3)
concentration = moles/volume
What is the equation for concentration? (g/dm^3)
concentration (g/dm^3) = concentration (mol/dm^3) x Mr
What is the display formula?
Shows us the arrangement of atoms and bonds in the molecule.
What is the structural formula?
Shows the arrangement of atoms in a molecule.
What is an alcohol?
An alcohol contains the functional group -O-H
What are the properties of alcohols?
Chemical:
- Liquids at room temperature
- Volatile
- Colourless
- Miscible with water
Physical:
- Flammable
What are the two methods of ethanol production?
Fermentation and hydration of ethene
Describe the fermentation method to make ethanol
starting materials:
renewable resources such as sugar beet, sugar cane or corn
catalyst:
enzymes in yeast (yeast is added to a sugar or starch solution)
method:
leave the solution at 30-40 degrees for several days in the absence of air. Enzymes in the yeast convert the sugar into ethanol and carbon dioxide. They require anaerobic conditions and get denatured if the temperature is too high. The sucrose reacts with water to be converted to glucose and fructose are converted into ethanol and carbon dioxide.
pros and cons:
+ much cheaper and easier
- only made in batches
- impure product (<15%)
- takes several days
equation:
C6H12O6 –> 2C2H5OH +2CO2
glucose –> ethanol + carbon dioxide
Describe the production of ethanol through the hydration of ethene…
starting materials:
non renewables (from crude oil)
catalyst:
phosphoric acid
method:
the reaction is carried out at 300 degrees and 60-70 atmospheres pressure with phosphoric acid. the reaction is a continuous flow process (very efficient). only a small proportion of ethene reacts at first, but the ethanol produced is condensed and the unreacted ethene is recycled so the product is very pure with a yield close to 100%
equation:
CH2=CH2 + H2O –> CH3CH2OH
ethene + steam –> ethanol
what is crude oil
crude oil is a mixture of hydrocarbons
how do you name alkenes
5 - methyl - 2 - hexene
5-methyl:
methyl - branch length
5 - location of branch
2-hexene:
hexene - longest chain length
2 - location of double bond
double bond takes priority when minimising number (eg. 5-methyl-2-hexene instead of 2-methyl-5-hexene)
how can bromine be used to distinguish between an alkane and an alkene?
bromine water will go colourless when mixed with an alkene
what is the difference with melting and boiling points between a pure substance and a mixture
a pure substance has a fixed melting and boiling point
a mixture may melt or boil over a range of temperatures
what is the industrial process used to separate crude oil into fractions and how?
it is called fractional distillation
During the fractional distillation of crude oil:
heated crude oil enters a tall
fractionating column
, which is hot at the bottom and gets cooler towards the top
vapours
from the oil rise through the column
vapours
condense
when they become cool enough
liquids are led out of the column at different heights
Small hydrocarbon molecules have weak
intermolecular forces
, so they have low boiling points. They do not condense, but leave the column as gases. Long hydrocarbon molecules have stronger intermolecular forces, so they have high boiling points.
what is a fuel
a substance that, when burned, releases energy
what happens in car engines to nitrogen and oxygen?
nitrogen and oxygen in the air react, forming oxides of nitrogen due to the high temperature reached
what can happen in the combustion of some impurities in hydrocarbon fuels
the formation of sulfur dioxide of nitrogen oxide. these contribute to acid rain
what is a hydrocarbon?
A hydrocarbon is a compound that is made out of only hydrogen atoms and carbon atoms.
