Unit 1 Questions Flashcards
Suggest why petrol should not contain a high proportion of heptane
- To prevent pre-ignition/knocking
- Burns less efficiently
- Does not combust efficiently
Write the equation for reforming heptane into cycloheptane
C7H16 —> C7H14 + H2
Explain how oxides of nitrogen can cause damage to trees
- Oxides of nitrogen react with water to form nitric acid
- Acid rain is produced
- Leeches into soils
Give a reason why the logarithm of ionisation energy rather than just ionisation energy is used to plot this graph
- Range of numbers are too large to fit on the axes
- Logarithms make it easier to plot numbers
Explain why the first ionisation energy of oxygen is lower than that of nitrogen
- Oxygen atom loses electron from 2p orbital
- Electron is paired
- Spin pair repulsion makes it easier for an electron to be removed
- Less energy required to remove an electron
- Nitrogen atom loses and electron from a singly occupied orbital
Explain why () does not show geometric isomerism
Two identical functional groups on each carbon
Or
there are not 2 different functional groups on each carbon
Reagent needed for oxidation of alkene into ketone
Acidified potassium manganate
Colour change when acidified potassium manganate is added to alkene
Purple to colourless
Explain why () is the major organic product
Tertiary carbocation is more stable than primary carbocation as it has more alkyl groups attached
Explain why aluminium chloride in the solid state has significant covalent character
- Aluminium ion is very small and highly charge, high charge density
- Polarises the chloride ion
Or
- Small difference in electronegativity between aluminium and chlorine
- So the electrons are partially shared
Describe how two AlCl3 molecules are joined together in the dimer
- Dative covalent bonding
- Two AlCl3 molecules joined together through two chlorine atoms
Explain what can be deduced from the graph about the electronic structure of nitrogen
- Large jump between ionisation energies 5 and 6 shows start of a new quantum shell
- Two electrons in the inner quantum shell as they are to remove and they are closer to the nucleus
- Five electrons in outer most shell as they are easier to remove and are further from the nucleus
Explain why () is considered as a carbon neutral fuel
- CO2 released is equal to CO2 absorbed
- CO2 released during combustion
- CO2 absorbed during photosynthesis
Explain how the use of fossil fuels cause climate change
- Combustion of fossil fuels produce carbon dioxide which is a greenhouse gas
- Increases greenhouse effect which leads to global warming
Name the process where long chain alkanes and converted into small more useful molecules including alkene s
Cracking
Give a test for alkenes, including the positive result
- Add bromine water
- Positive result: bromine water decolourises (brown to colourless)
Suggest how hydrogen chloride could be removed from the waste gases produced in an incinerator
- Use of basic/alkaline scrubbers to form a precipitate
- Injected of powdered activated carbon to the flue
- Pass through water/dissolve HCl in water
Explain two ways in which the physical properties of diamond and graphite differ, refer to their structure and bonding in your answer
- Diamond is hard, graphite is soft
- Diamond has a rigid lattice, graphite has weak forces between the layers in graphite
- Graphite conducts electricity, diamond does not
- Graphite has free delocalised electrons, diamond does not
State a use for graphene, identifying the property that makes it suitable for that use
- Oxidation resistance layer because it is unreactive
- Flexible electronics because it is one atom thick and conducts electricity
Give the reagents and conditions: CH2=CH2 —> CH3CH2OH
Stem and acid catalyst
Give the reagents and conditions: CH2=CH2 —> CH2OHCH2OH
Potassium manganate solution in sulphuric acid
Explain why the first ionisation energy of phosphorus is greater than that of sulfur
Phosphorus
1. Electron is removed from 3p orbital which is half filled, p orbitals are singly occupied
2. More energy is required to remove an unpaired electron than a paired electron
Sulfur
1. Electron is removed from 3p orbital where the outermost electron is paired
2. Less energy is required to remove a paired electron due to spin pair repulsion
Explain why the melting temperature of phosphorus is much lower than that of silicon
- Silicon has a giant covalent structure
- Strong covalent bonds between silicon atoms
- Phosphorous has a simple molecular structure
- Much more energy is needed to break the covalent bonds in silicon than to overcome the intermolecular forces in phosphorus
Explain the difference in first ionisation energies of chlorine and bromine
- Chlorine has a higher ionisation energy
- (Although) the nuclear charge is lower
- Outer electron is in a lower energy level
- Outer electron is closer to nucleus
- Outer electron experiences less shielding
Explain why chlorine has a low boiling temperature
- Simple molecular structures
- Weak forces between molecules
- Little energy required to overcome these forces
Explain, with reference to structure and bonding, why silicon has a very high melting temperature
- Giant molecular structure (macro molecular)
- Covalent bonds
- Many strong covalent bonds between silicon atoms
- Each silicon atom is bonded to four others
- Large amount of energy required to break
Describe how metals conduct electricity
- Metals contain delocalised electrons
- Which an move freely through the structure when a potential difference is applied
Give a possible reason why aluminium has a higher electrical conductivity than sodium
- More delocalised electrons
- Aluminium has three delocalised electrons
- Sodium has one ion
Give a reason why aluminium must be in the liquid state before electrolysis
Ions must be mobile to allow a current to flow
State what is meant by the term orbital
An region within an atom that can hold up to two electrons/where there is a high probability of finding an electron
Describe what can be deduced about the electronic structure of sodium from its successive ionisation energies
- Three quantum shells
- 2,8,1
- First electron is removed from the third shell
- Has one electron in its outermost shell
- 8 electrons in second quantum shell
Suggest why the fourth ionisation energies of neon and sodium are similar in magnitude even though the elements are in different periods o the periodic table
The fourth electron is removed from the same quantum shell
State the meaning of the term biodegradable
Can be broken down by organisms/decayed by bacteria/degraded
Give three advantages of biodegradable polymers
- Takes less time than most plastics to break down
- Reduces waste going to the landfill
- Reduces pollution
- Breakdown into non harmful products
- Can be used as fertiliser
- Help conserve crude oil reserves
- Come from a renewable resource
- More sustainable
State why () does not have geometric isomers
Two identical groups attached to one carbon of the double bond
Give a reason why a double bond may result in geometric isomerism
- Does not allow free rotation
- Restricted rotation around double bond
Explain why the first ionisation energy of sulfur is less than the first ionisation energies of both phosphorus and chlorine
- Outermost electrons in same subshell
- Similar shielding
- Chlorine has the higher nuclear barge
- Chlorine has more protons than sulfur
- Sulfur has a half filled 3p subshell
- Spin pair repulsion in p orbital
State what is meant by the term isotopes, in terms of subatomic particles
- Atoms of the same element that ave the same number of protons
- Different number of neutrons
Explain why PCl5 has a higher melting temperature than SbCl5
- Strong ionic bonds/lattice in PCl5
- Stronger electrostatic attraction
- SbCl5 simple molecular structure
- Weak intermolecular forces
State what is meant by the term dative covalent bond
Shared pair of electrons in which both atoms come from the same atom
State one similarity and one difference that would be seen when propane is mixed with separate samples of acidified potassium manganate solution and of bromine water
- Both solutions decolourise
- Potassium manganate= purple —> colourless
- Brome water= orange —> colourless
Explain why () exhibits geometric isomerism and has only two geometric isomers
- Restricted rotation around double bond
- Only central C=C bond has two different groups attached to each carbon of the C=C
State what is meant by the term structural isomers
Compounds with the same molecular formula and different structural formula
Give a reason why incomplete combustion sometimes occurs
Limited supply of air/insufficient oxygen available
Give a reason for adding cycloalkanes to petrol
- Prevents knocking/pre ignition
- Burns more efficiently
Suggest an explanation for the decrease in atomic radius as atomic number increases across a period
- As the atomic number increases, the nuclear charge increases
- Partially offset by the increased electron-electron repulsion as the number of electrons increases
- The electrons are all the same quantum shell experience similar shielding
- Increase in attractive force between nucleus and outer electrons
Describe how a covalent and dative covalent bond is formed
- A covalent bond is when electrons come from bot atoms
- A dative covalent bond is when a lone pair of electrons are donated from only one atom
Explain why gaseous beryllium chloride and solid calcium chloride have different types of bonding
- Beryllium is smaller as it has fewer electron shells
- Higher charge density than calcium
- More polarising than calcium
- Smaller difference in electronegativity
- Beryllium-chloride bond has a higher degree of covalency
Explain why aluminium is in group 3 by looking at its ionisation number and energy
- Significant jump between 3rd and 4th ionisation energies
- 4th electron is removed from a different quantum shell (closer to nucleus)
- 3 electrons in outer most shell
Explain the general increase in ionisation energy from sodium to argon (across period 3)
- Number of protons increases
- Nuclear charge increases
- Similar shielding
- Additional electrons are in the same energy level
Explain why the first ionisation energy of aluminium is less than the first ionisation energy of magnesium
- Aluminium- first electron is removed from the 3p orbital
- Magnesium- first electron is removed from the 3s subshell
- P electrons are shielding by the S electrons so requires less energy to be removed
Describe the bonding in aluminium metal
Strong electrostatic attraction between positively charged metal cations and a sea of delocalised electrons
Give two reasons why aluminium is used for overhead power cables
- Has free delocalised electrons which can carry charge
- Aluminium has a low density (light weight)
- Aluminium is ductile and can be drawn into wires
- Aluminium forms an inert layer
Give two possible reasons for producing hydrogen from aluminium rather than from fossil fuels
- Reduces green house gas emissions
- Reduces carbon dioxide emissions which affects climate change
- Production of hydrogen is portable
- Fossil fuels are non renewable
- Aluminium can be recycled
Describe how a sample of octadecane can be obtained from a mixture of alkanes
- Fractional distillation
- Mixture is vapourised
- Distillate condenses at suitable temperature range
Product of Alkene + steam
Alcohol
Product of Alkene + Cl2
Disubstituted halogenoalkane
Product of alkene + steam and nickel catalyst
Alkane
Product of alkene + acidified potassium magnate
Diol
State one advantage and one disadvantage of using incineration for the disposal of polymers, other than effect on climate
Advantages
1. Can be used to generate electricity
2. Prevents polymers from going to landfill
Disadvantages
1. Toxic, harmful, corrosive
2. Particulates may be produced
State how the graph confirms that barium is in group 2 of in the periodic table
- Large increase in ionisation energy
- Between 2nd and 3rd ionisations
Give a reason why solid barium chloride does not conduct electricity
Ions are not mobile so a charge cannot be carried
Name the industrial process used to covert octane into isooctane
Reforming
Give a reason why () is the major product
The tertiary carbocation is more stable than the primary carbocation
Explain what is meant by isotopes
Atoms of the same element with the same number of protons and different number of neutrons
Give two ways in which chemists can help minimise problems caused by the disposal of polymers
- Develop biodegradable polymers
- Remove toxic gases produced by incineration
- Develop processes to covert polymers back into feedstock
- Use IR spectroscopy to separate polymers for recycling
