Ozone Story Flashcards
What are the units for electronegativity
Has no units
What scale is electronegativity measured on
Pauling scale as Linus Pauling suggested this method
What happens to electronegativity across a period
Increases
What happens to electronegativity down a group
Decreases
What two factors effect how strongly an atom attracts its shared electrons
Atom size and closeness to nucleus
Size of core charge
How does the atom size effect electronegativity
Smaller can get closer to electrons
Has a larger attraction
How does the size of core charge effect electronegativity
Higher nuclear charge has more attraction
How does a permanent dipole occur
When two atoms in a bond have very different electronegativities
What happens if two atoms do not have a very big electronegativity difference
No overall dipole even though bonds can still be polar
Why does CCl4 have no overall dipole due to its shape
Is tetrahedral
Chlorine carries small negative charge, central car in positive
Centre of negative charge midway between all chlorines
Centre molecule, positive charge put on carbon
Dipoles cancel due to molecule symmetry, no overall dipole so is non-polar
How is a permanent dipole-permanent dipole bond made
Not made it is molecule attraction e.g hydrogen chloride attract each other quite strong
Can a dipole form without a permanent droplets
Yes from electronegativity similarities
How is a permanent dipole - induced dipole bond made
If add a molecule with a permanent dipole next to a non-polar molecule the permanent dipole induces a dipole.
How does an instantaneous dipole - induced dipole bond form
Instantaneous dipole forms due to an unequal distribution of electrons in induced dipole molecule, has a temporary dipole (lasts short time)
Can effect molecule with no dipole
What must molecules have for hydrogen bonding
Large dipole between hydrogen atom and highly electronegative atom
Small hydrogen atom that can get very close to atoms in nearby molecules
Lone pair of electrons that positive hydrogen can line up with
Dipole-dipole bonds in all hydrogen halides, which has the highest boiling point and why
Hydrogen fluoride highest as has hydrogen bonding
What happens to electronegativity of halogens down group
Decreases as get bigger down group as more electrons
What is different about waters structure of bonding
Oxygen has two lone pairs for can form twice as many hydrogen bonds
why do liquids with hydrogen bonding have a higher viscosity
To flow past each other need to break binds, stronger the bond - hydrogen bonding, more difficult
Why are substances with hydrogen bonds often more soluble in water
Hydrogen bonds form between water and substance
How does ice have an open structure
Has four groups round each oxygen atom, maximises hydrogen bonds between them
What is viscosity
How easily liquid flows
What is collision theory
Reactions occur when particles react with minimum kinetic energy
Not all collisions cause reaction
Existing bonds stretch, new bonds form
Only pairs with enough energy to overcome activation energy react
What is an enthalpy profile
Shows the energy of reacting particles before, during and after reaction
What is activation enthalpy
Minimum kinetic energy of particles need to react
What methods are there if measuring rate of reaction
Collecting gas - use volume of gas made
Mass change - lose mass, gas made
Colour - colorimeter, light percentage pass through substance
pH - titration/neutralisation
Chemical analysis- sample reaction moisture at regular intervals, stop reaction (quench) before analysis
How does temperature effect rate of a reaction
Increase temperature on average particles have more kinetic energy so move faster
More molecules will have activation energy, reaction faster
What happens to Boltzmann distribution curve when increase temperature
Pushes it to right
What happens to the total number of molecules in area under curve when increase temperature
Stays same
Why are not all collisions successful
Particles must have activation energy of more to react
Particles must approach in correct orientation for reaction to take place on collision - steric factor
How does a catalyst effect a reaction
Spreads yo reaction, provides alternative route from reactants to products with lower activation energy
Chemically unchanged at end of reaction
What is homogenous catalysis
Catalyst and other reactants all in gaseous state in atmosphere
How does homogenous catalysis work
Form an intermediate in first step, changed back to catalyst in second step
How is percentage changed into parts per million (ppm)
x 10000
How is parts per million changed into percentage
Divide by 10000
How are haloalkanes named
Start from end of chain that will give smallest numbers
Alphabetical order if more than one halogen
Use e.g ‘di-‘ if two
What is a primary haloalkane
Halogen on end of chain
What is a secondary haloalkane
Halogen atom attached to carbon atom in middle of hydrocarbon chain
What is a tertiary haloalkane
Halogen attached to carbon on atom which carry no hydrogen atoms
What is electronegativity
Ability of an atom in a covalent bond to attract shared electrons to itself
