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115 Cards in this Set
- Front
- Back
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What are the 5 gases are most prevalent in the air?
And what are there concentrations? |
Nitrogen- 78% Oxygen- 21% Argon- 1% Carbon dioxide- 399 ppm Neon- 18.2ppm |
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Where are the majority of the molecules in the atmosphere? |
• 90% of all molecules are in the troposphere |
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What happens to the atmosphere the higher you go? |
It becomes less dense |
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What are the 4 sections of the atmosphere and what distances in the air are they at? |
Troposphere: 0-15km Stratosphere: 15-50km Mesosphere: 50-80km Thermosphere: 80-100km |
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Where is the ionosphere? |
It starts in the mesosphere and extends 550km above the Thermosphere |
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How do we express the conc. of a gas if it's small |
Parts Per Million (PPM) by Volume |
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How do u calculate % composition of gases? |
Step 1: Divide the number of gas molecules by 1,000,000 Step 2: Multiply answer by 100 to get % |
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How do calculate concentration in PPM? |
Step 1: Multiply the % by 10,000 |
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What was the early atmosphere made up of? |
Mainly CO2, Methane, Ammonia |
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What converted the CO2 into O2 |
Plants |
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What happened when oxygen levels reached 10%
What are the oxygen levels steady at now? |
Animal life appeared 21% |
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What are the main human activities that cause... CO2 CH4 NOx CO |
CO2- Combustion of hydrocarbon fuels & deforestation CH4- Cattle Farming, landfill sites & natural gas leakage NOx- Fertilised soils CO- Incomplete Combustion of hydrocarbons |
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How is ozone created? |
• UV acts on O2 & H2O creating oxygen radicals O2 > O• + O• • O2 atoms then react with radicals to form ozone O2 + O• > O3 |
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What type of electromagnetic radiation can cause skin cancer and why? |
UV It's highly ionising as it can damage DNA. |
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Name the three types of UV Radiation, their frequency and how they affect the skin? |
•UV-A: Quick tan, 8-9x10^14 •UV-B: Tanning, 10x10^14 •UV-C: Burning, 11-12x10^14 |
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What do sunscreens contain to absorb high-energy UV radiation? |
•Benzene Rings or •Alternating double & single bonds |
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How does ozone in the stratosphere help humans? |
It absorbs and is broken down by UV, but stops UV reaching |
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What is the equation for light as a wave? What is the equation for light as a photon? |
• Speed of Light = Frequency x Wavelength • Energy of a Photon = hf |
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What are the 4 aspects of behaviour dependent on energy? |
1) Translational Energy (Molecule movement as a whole) 2) Rotational Energy (Molecule rotation as a whole) 3) Vibrational Energy (of individual bonds) 4) Electron Energy (changes when an electron moves from 1 level to another) |
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Vibrational Energy corresponds to what radiation? Size of Energy? What does it cause? |
Infrared radiation 1x10^-20 to 1x10^-19 J Makes molecules in the skin vibrate more energetically. |
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Rotational Energy corresponds to what part of the spectrum? What is the size of Energy? |
Microwave radiation 1x10^-22 to 1x10^-20 |
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What Energy requires the least Energy? |
Translational |
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Electron Energy needs enough energy to ........... Corresponds to what radiation? Size of Energy ? |
• Excite electrons to higher energy levels • Visible/ UV part of the spectrum • 1x10^-19 to 1x10^-16 |
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UV radiation incident on Cl2 can cause 3 processes based on the Energy absorbed & which requires the most energy |
1) Ionisation- most Energy Cl2 > Cl2+ + e- So that an electron is able to leave 2) Dissociation- Cl2 > Cl + Cl So that the bonding can no longer hold atoms together 3) Release of Energy |
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How thick is ozone? |
3mm, easily damaged. |
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What does bond-breaking involve? |
The redistribution of electrons in the bond |
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What happens in Heterolytic Fission? Why does occur? Give an example? |
•When the bond breaks the shared electrons go to one of the atoms •When a bond is polar • HCl > H+ & Cl- |
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What is Homolytic Fission? Give an example of this? When does a polar bond break like this? |
• When the bond breaks the electrons go one to each atom • Br-Br > Br• + Br• • A polar bond breaks like this in the gas phase in the presence of light |
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The amount of energy required to break a bond depends on |
Bond Enthalpy |
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How is ozone formed from human activity? |
Electric Motors, Photocopiers or UV lamps. |
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What is the reaction that initiates the creation of ozone? |
O2 > O• + O• |
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What reactions kept ozone in a steady state for years? |
O• + O2 > O3 O• + O• > O2 O• + O3 > O2 + O2 |
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O3 >UV> O2 + O• What happens in this reaction and why is it vital? |
• Ozone absorbs radiation & undergoes photodissociation • Reaction has vital screening effect of ozone as it absorbs radiation that would cause skin cancer. |
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What do radicals do? |
They are reactive and tend to fill their outer shell by grabbing an electron from another atom |
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An example of a radical reaction: Cl• + H2 > HCl + H• Explain what happens: What does the hydrogen radical do? |
• The Cl radical collides with the H2 and grabs an electron from the pair of electrons in the bond. • The H• radical will combine with another molecule resulting in another radical being formed. |
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What are the three stages of a radical chain reaction: What happens every stage- |
Initiation- Radicals formed Propagation- Radicals react to form radicals. Termination- Two radicals collide to form an atom |
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What is the overall effect of a chlorine radical chain reaction: |
H2 & Cl2 converted to HCl |
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What happens when alkanes are involved in chlorine radical reactions,Overall Effect? E.G: Methane and chlorine |
• HCl, Chloromethane & some ethane are produced • Some Dichloromethane & trichloromethane may also form. |
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Which reaction is initiation, propagation & Termination?
1) Cl• + Cl• > Cl2 2) CH3• + Cl2 > CH3Cl + Cl• 3) Cl2 >UV> Cl• + Cl• |
1) Termination 2) Propagation 3) Initiation |
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•What is Rate of Reaction? •2 examples of fast reactions •2 examples of slow reactions |
•The rate at which reactants are converted into products •Burning fuel in a car engine & Precipitating silver Chloride
•Souring of Milk & Rusting of iron |
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Equation for the rate of reaction- |
Rate of Reaction= Change in Property / Time taken |
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Equation for the rate of reaction- |
Rate of Reaction= Change in Property / Time taken |
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How can measuring the volume of gas be used to monitor reaction rate? Give example |
CaCO3 + HCl > CO2 •Bubble CO2 through water into a measuring cylinder |
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What is another way of measuring reaction rate? |
PH Measurement- As the above reaction happens the HCl conc. will fall as it reacts with CaCO3. So measuring the PH of the reaction is another way of monitoring it. |
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What is Calorimetry? |
Measures the change in colour of a reaction |
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What is Calorimetry? |
Measures the change in colour of a reaction |
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Name the 4 factors that affect Reaction Rate? |
Temperature Concentration/Pressure Particle Size/Surface Area Catalysts |
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What is Calorimetry? |
Measures the change in colour of a reaction |
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Name the 4 factors that affect Reaction Rate? |
Temperature Concentration/Pressure Particle Size/Surface Area Catalysts |
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How does Temp. affect reactions? |
• The Ek particles have • The speed of particles & how frequently they collide • The likelihood of the collisions having enough energy to react |
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What is Calorimetry? |
Measures the change in colour of a reaction |
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Name the 4 factors that affect Reaction Rate? |
Temperature Concentration/Pressure Particle Size/Surface Area Catalysts |
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How does Temp. affect reactions? |
• The Ek particles have • The speed of particles & how frequently they collide • The likelihood of the collisions having enough energy to react |
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How does Conc./Pressure affect Reactions? |
• The amount of particles in a set volume • Dictates how likely collisions are to occur |
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What is Calorimetry? |
Measures the change in colour of a reaction |
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Name the 4 factors that affect Reaction Rate? |
Temperature Concentration/Pressure Particle Size/Surface Area Catalysts |
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How does Temp. affect reactions? |
• The Ek particles have • The speed of particles & how frequently they collide • The likelihood of the collisions having enough energy to react |
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How does Conc./Pressure affect Reactions? |
• The amount of particles in a set volume • Dictates how likely collisions are to occur |
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How does particle size/ surface area affect reactions? What reacts faster powder or a lump? |
• The more surface area exposed the more places there are for collisions to occur • Powder reacts faster |
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How do Catalysts affect reactions? |
•They increase the rate of reaction without affecting the products • By offering an alternative route for the reaction that has a lower activation enthalpy |
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What does an enthalpy profile show? |
The reaction progress against enthalpy |
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What does an enthalpy profile show? |
The reaction progress against enthalpy |
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What is Transition State? |
Where old bonds stretch & new bonds start to form. This exists for a very short time |
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What does an enthalpy profile show? |
The reaction progress against enthalpy |
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What is Transition State? |
Where old bonds stretch & new bonds start to form. This exists for a very short time |
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What are the axis for a Maxwell-Boltzmann distribution? |
Y-Axis: Number of particles with kinetic energy X-Axis: Kinetic Energy |
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What is used to show the distribution of energies? |
Maxwell-Boltzmann Distribution |
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What is a Homogenous Catalyst? How does it work? An Example of Homogenous Catalysis? |
• Are in the same physical state as the reactants in the reaction. • It forms an intermediate compound with reactants (transition state) The intermediate compound then breaks down to give the product & reform the catalyst •Is the destruction of the ozone in the stratosphere by chlorine & bromine atoms |
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CFC's used for.... |
Refrigerants AC Units Aerosol Propellants Dry Cleaning solvents |
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How do we name Haloalkanes? |
• The Halogen is used as the prefix E.G: Chloro, Bromo, Fluoro
• The base of the name comes from the parent Alkane E.G: Ethane, Propane, Butane |
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What dictates the properties of Haloalkanes? |
The Carbon-Halogen bonds being polar. |
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How are partial charges caused? |
When there is a more neg. end of the bond & a more pos. end of a bond. Caused by electrons being unevenly distributed |
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What is electronegativity? What does the difference in it have to be for a bond tone polar? What is used to derive Electronegativity? |
•It is a measure of the ability of an atom in a molecule to attract electrons in a chemical bond to itself • A difference of 1 • The Pauling Scale |
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What is the electronegativity trend for the halogens? Which is the most electronegative element? |
• The electronegativity increases as you go up the group of Halogens • Fluorine is the most electronegative element |
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Properties of Haloalkanes: • How do they act with water • Boiling points? |
• Haloalkanes are all immiscible in water (Cannot be mixed) • B.P's depend on how big the halogen is, the larger it is the higher the B.P |
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What are intermolecular bonds? |
The bonds that cause molecules to be attracted to one another |
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Why does boiling point indicate the strength of the IM Bonds? |
When a solid melts or boils these bonds are broken. |
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In relation to IM, The longer the Hydrocarbon ..... • Do Straight chain alkanes or Branched isomers have stronger IM forces and why? |
•The Stronger the IM Forces • Straight chain alkanes have stronger IM forces because they can pack closer together than branched isomers |
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Explain How do Catalysts work? |
• They speed up reactions by providing an alternative reaction pathway with a lower activation enthalpy for breaking or remaking bonds. • They lower the energy barrier allowing more pairs of molecules to react when they collide so the reaction proceeds more quickly |
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When is there a dipole? |
An uneven balance of charge across a bond. Due to an uneven distribution of electrons |
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3 Different types of IM forces? And the strongest and weakest? |
1) Instantaneous dipole - Induced dipole/ id-id/ weakest 2) Permanent dipole - Permanent dipole/ Pd-Pd 3) Hydrogen Bonding/ Strongest |
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How is an Induced dipole caused? |
• Occurs when an unpolarised molecule is next to a dipole. • The dipole attracts or repels electrons in the unpolarised molecule inducing a dipole in it. |
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When do Permanent dipoles occur? Give an example? |
•Occurs when 2 atoms in a bond have clearly different electronegative's. • HCl has a P.d because Cl is much more electronegative than hydrogen, so attracts the shared electrons more. |
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How can a molecule with polar bonds have no overall dipole? Give an example: |
Bonds can be polar but have their charges cancel each other out through their structure E.G: CCl4; the Cl atoms are in a tetrahedral shape so even though the C-Cl bonds are polar they cancel out. |
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Id-Id forces can act between.... But Most noticeable in...... •What are the 2 main effects on the strength of id-Id forces |
All molecules In Non-Polar substances
The more electrons an atom has the stronger the id-id forces are Shape being straight chain molecules because Id-Id forces can be maximised unlike in branched isomers |
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Halogens are ............ molecules Halogens strongest IM bonds? What does this mean for their boiling points? |
Non-Polar/Diatomic molecules Id-Id forces This means the smaller the halogen the smaller the weaker the id-id forces, the lower the BP. |
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What molecule is important for removing Cl radicals from the atmosphere? |
Methane CH4 + Cl > CH3 + HCl |
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What does a chlorine reservoir molecule do and give an example. How are these molecules dealt with? |
• They store Cl in the stratosphere E.G: HCl & ClONO2 • These molecules can be rained out of the stratosphere Or • Just save Cl until hit with UV, resulting in consequences |
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What is hydrogen bonding a special case of? When does H.Bonding occur? Example of atoms that bond to Hydrogen in this way? |
•A special case of Pd-Pd Bonding • When a Hydrogen atom is bonded to atoms with high electronegativity • Fluorine, Oxygen, Nitrogen |
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How do chlorine and bromine radicals form in the stratosphere? |
Small amounts of Chloromethane & Bromomethane reach the stratosphere where they are split up by solar radiation to give Cl & Br radicals. |
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List the 3 things needed for H.Bonding? |
1) Large dipole between hydrogen atom and highly electronegative atom. 2) Small hydrogen atom to allow it to get very close to atoms such as oxygen in nearby molecules. 3) A lone pair of electrons on the oxygen, nitrogen or fluorine atom that the pos. charged hydrogen can line up with. |
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How can the strength of hydrogen Bonding be seen through the hydrogen halides? |
H-F has the strongest boiling point even though it has the lowest molecular mass. All hydrogen halides have dipole-dipole bonds but because electronegativity decreases down the group. |
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Why can Water form twice as many hydrogen bonds as HF? |
Because it's oxygen atom has two lone pairs of electrons and has twice as many hydrogen atoms as the oxygen atom.
•Whereas HF has 3 lone pairs but only 1 hydrogen so only one bond can be made. |
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What does hydrogen Bonding in liquids cause? And why is this caused? |
High Viscosity (Hard for the liquid to flow) This is because for liquid to flow the molecules must be able to move past each other this requires constant breaking and forming of IM Bonds. The stronger these bonds are the harder it becomes. |
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Are substances with Hydrogen Bonding soluble in water or not? And Reasoning for answer? |
Yes The dissolving process helped by Hydrogen bonds between the water & the substance |
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What happens when water freezes to the IM bonds? |
It has an open structure with 4 groups around the oxygen atom. Maximising the H.Bonding between them |
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What can be formed when a carbon-halogen polar bond is broken by heterolytic fission? |
A Neg. halide ion & a pos. Carbocation |
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Explain how another heterolytic fission can occur? And the following reaction? |
When a positively polarised carbon atom reacts with a neg. charged substance. This will cause a substitution reaction. |
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Define substitution? Define Nucleophile? |
A reaction where one atom or group in a molecule is replaced by another
Is a neg. charged molecule or ions with a lone pair of electrons that it can donate to a pos. charged atom to form a covalent bond |
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What are the steps for nucleophilic substitution- using 1-bromobutane & OH- ions |
Step 1) The nucleophile (OH) attacks the electron deficient carbon atom in the C-Br bond. Step 2) The (OH) donates 2 electrons to form a new dative covalent bond Step 3) The C-Br bond breaks heterolytically & the Br atom receives 2 electrons, producing a Br ion. Known as the leaving group. |
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What is the product of the Cl• & Br• reacting with ozone? |
Cl• + O3 > ClO• + O2 Br• + O3 > BrO• + O2 |
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Name 6 common Nucleophiles |
Hydroxide Ion (OH) 3 lone pairs Cyanide ion (CN) 2 lone pairs Ethanoate ion (CH3COO) 3 LP's Ethoxide ion (C2H5O) 3 LP's Water (H2O) 2 lone pairs Ammonia (NH3) 1 lone pair |
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When does water act as a nucleophile? What is the difference between water as nucleophile and OH ions? |
•When the two are heated together under reflux; the water attacks the Haloalkane • The reaction takes place slower than OH reactions |
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What is the first step of this reaction? What is the 2nd step of this reaction? Known as a ........ Reaction |
1) Halogen replaced by H2O 2) One of the hydrogens from the H2O is forced off the molecule leaving the Oxygen with two lone pairs and a H+ ion produced to join the Halogen ion. |
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When does Ammonia work as a nucleophile? What is the product of this reaction? |
When the Haloalkanes is heated in a sealed tube with conc. ammonia solution. The product is an Amine with an NH2 group. |
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What is the structure/ example of the amines? |
H3C-NH2 = Methylamine Also Ethylamine & propylamine They act similar to alcohols in structure |
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What happens if u reverse a hydrolysis reaction? What acts as the nucleophile? What condition is it done under? |
A Haloalkane can be produced from an alcohol Halide ion In the presence of a strong acid |
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What is the first step of this reaction? What does this cause Explain 2nd step: & what else is produced |
H+ ion joins with one of the lone pairs from the oxygen on the alcohol. This causes the carbon atom the oxygen is attached to, to have a higher partial pos. charge. 2nd step- the halide ion attacks the C-O bond and the H20 breaks off heterolytically. The Br ion joins the molecule and water is produced. |
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Strong bonds between carbon-halogens means ......... Bond polarity of C-F is ....... than C-I Therefore C-I is the easiest to .... Hence ...... & ....... compounds are used in synthesis |
High Bond Enthalpy Higher Hydrolyse Bromo & iodine |
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What reaction wouldn't matter if the reaction between O3 & O was faster than it? How much faster is the other reaction though? |
O3 & Cl 1500 times faster |
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What is the overall reaction of chlorine and ozone? |
Cl + O3 > ClO + O2 ClO + O > Cl + O2 Overall reaction: O + O3 > 2O2 |
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A single Cl atom can remove how many Ozone molecules? But how much more effective is bromine at destroying ozone? |
•1 Million Ozone molecules •Bromine is 100 times more effective at destroying ozone than Cl |
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How are Hydroxyl Radicals formed? How do they react with Ozone? |
• Formed by the reaction of O2 atoms with water
• HO• + O3 > HO2• + O2 HO2 + O• > HO• + O2 |
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What is odd about NO & NO2 Radicals? |
They are both relatively stable molecules |
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What does CFC stand for? |
Chlorofluorocarbon's |
