Unit 1 - chemical changes and structure Flashcards
How does particle size affect the rate of reaction
- smaller particle size
- larger surface area
- increased successful collisions
- faster rate
How does concentration affect reaction rate
- higher concentration
- more particles present in given volume
- more successful collisions
- faster rate
What causes particles to have an kinetic energy greater than or equal to the activation energy
Increase in temperature
How can a reaction be made more economical
Lower temperature and add a catalyst
Will adding a catalyst raise or lower the activation energy
Lower activation energy
How is the activation energy found from a potential energy diagram
From the reactant (R) to the peak of the graph
When calculating the potential energy of a reaction from a potential energy diagram how can you tell if reaction is exothermic or endothermic
Exothermic - negative value for H, R higher than P
Endothermic - positive value for H, P higher than R
How could the reverse reaction be found
By switching R and P around
What is the covalent radius
Measure of the size of an atom
What is ionisation energy
Energy required to remove one mole of electrons from one mole of gaseous atoms
What is electronegativity
The attraction an atom of an element has for bonding electrons
As you go across the periodic table why does covalent radius decrease
- increased nuclear charge
- pulls electrons closer
Why does first ionisation energy increase as you go across the periodic table
- increased nuclear charge
- smaller radius
- outer electrons more tightly held
Why does electronegativity increase as you go across the periodic table
- increased nuclear charge
- smaller radius
- outer electrons more tightly held
As you go down the periodic table why does covalent radius increase
Increased number of electron shells
Why does first ionisation energy decrease as you go down the periodic table
- increased number of shells
- atom bigger
- electrons further from nucleus
- increased shielding effect by inner electrons
- outer electrons less strongly held
Why does electronegativity decrease as you go down the periodic table
- increased number of shells
- atom bigger
- electrons further from nucleus
- increased shielding effect by inner electrons
- outer electrons less strongly held
What is ionic bonding between
Metal + non-metal
Will ionic compounds conduct
Yes when in liquid or molten
What elements form a covalent network
Si, B, C
What type of bonding and structure forms between two non-metals
Covalent molecular
What are the boiling points of a metallic lattice like
Fairly high
What are the elements that form a monatomic structure
He, Ne, Ar
Will monatomic compounds conduct
No
What type of bonding stairs electrons
Covalent bond
What type of bonding transfers electrons
Ionic bond
If the electronegativity difference is zero what kind of bonding occurs
Pure covalent bonding or non-polar bonding
What difference of electronegativity what cause polar covalent bonding
> 0<=2
If a compound has an electronegativity greater than 2 what type of bond would be present
Iconic bonding
Does the element with the higher or lower electronegativity pull the electron closer
Higher electronegativity
What type of bonds are C-H always
Non-polar covalent
What type of molecules are deflected by a charged rod
Polar molecules
If all the bonds in a molecule are non-polar what type of molecule is it
Non-polar molecule
What type of molecule is formed when there are polar bonds present and the molecule is symmetrical
Non-polar molecule
What type of molecule is formed when there are polar bonds present and the molecule is non-symmetrical
Polar molecule
Do polar molecules have high or low melting/boiling points
High
What type of intermolecular forces are present in polar molecules
Permanent dipole to permanent dipole interactions
Do non-polar molecules have high pr low melting/boiling points
Low
What type of intermolecular forces do non-polar molecules have
London dispersion forces
How do Vander Waal forces occur
When electrons in atoms move randomly around forming slight temporary dipoles
When noble gases are in gas form is there an attraction between atoms
No, Van der Waal forces only from when gas is turned into a liquid
Why does the boiling point increase as you go down the noble gas group
- mass increases (atom gets bigger)
- boiling point increases
- due to stronger Van der Waal forces
Intermolecular forces are the attraction between what
Attraction between molecules
What are intramolecular forces
Holds atom together
Eg - polar covalent bonds
What are the 3 types of intermolecular forces
- london dispersion forces (LDF)
- permanent dipole to permanent dipole interactions
- hydrogen bonding
What type of intermolecular force has the strongest strength
Hydrogen bonding
What type of intermolecular force is the attraction between temporary dipoles
London dispersion forces
What elements does hydrogen bond to for hydrogen bonding
N, O or F (Nandos On Friday)
What causes more LDFs to be present
- bigger molecule
- more electrons
- higher melting/boiling points
- more LDF present
What effect does hydrogen bonding have on a molecule
- increased b.p/m.p
- increased viscosity
- increased solubility
Why is ice less dense than water
- hydrogen bonding
- causes ice to have an open/ expanded structure
What forces are broken when a covalent molecule melts
Van der Waal forces
What are ionic or polar molecules soluble in
Polar solvents (water)
What are non-polar or covalent molecular molecules soluble in
Non-polar solvents (pentane)
Are metals an covalent networks soluble or insoluble
Insoluble
