1) Chemical Changes and Structures Flashcards
Ways of speeding up rate of reaction (4)
using a catalyst
decreasing particle size // increasing surface area
increasing temperature
increasing concentration / pressure
Ways of measuring rate of reaction (3)
water displacement (vol gas produced) gas syringe (vol gas produced) difference in mass (vol mass change)
Why is it important that chemists can control rate of reaction? (2)
- to ensure that processes are both economically viable (they will result in a good yield of products and profits for the company)
- to ensure it is safe (the reaction does not progress too quickly potentially causing explosions).
The rate of a chemical reaction is proportional to the
concentration of reactants present. As reactants are used up during the process, the rate will decrease, and the reaction slows down.
ΔQ can be a: (3)
volume
mass
concentration / pressure
For a successful collision you need: (2)
activation energy
correct geometry
What does a catalyst do when added to a chemical reaction?
It lowers the activation energy, allowing more reactions to occur.
ΔH = ?
ΔH = Hproducts - Hreactants
What is the activated complex?
The unstable arrangement of atoms which is very high in energy.
What is ΔH?
enthlapy change
In an exothermic reaction is ΔH positive or negative?
negative
In an endothermic reaction is ΔH positive or negative?
positive
Why does increasing temperature increase rate of reaction?
Because more particles now have energy greater than or equal to the activation energy
Why does increasing concentration or pressure increase rate of reaction?
More of these reactant particles are moving in the same space making it more likely than before that they will collide and cause a successful collision
Collision theory states that
reactants must collide with the correct geometry and possess a minimum energy before a successful collision occurs
Characteristics of metallic lattice: (3)
strong bond, high melting point, good conductors
as we look from the _________ to the _________ of the periodic table we see COVALENT RADIUS increasing
top right to bottom left
as we look from the _________ to the _________ of the periodic table we see 1ST IONISATION ENERGY increasing
bottom left to top right
as we look from the _________ to the _________ of the periodic table we see ELECTRONEGATIVITY increasing
bottom left to top right
hydration is an example of a _____ reaction
addition
what is the activated complex
a high-energy unstable arrangement of atoms
the more level the potential energy diagram
the more stable the activated complex
Reminder: the greatest enthalpy change doesn’t have to be positive
the greatest enthalpy change doesn’t have to be positive
when liquid oxygen evaporates what forces are broken
London dispersion forces
what is the ionisation energy
the energy required to remove one more of electrons form one mole of gaseous atoms
an increase in ___________ causes the electrons to be more attracted to the nucleus
nuclear charge
an increase in __________ causes the outer electrons to be screened for the nucleus
electron shells
ionic vs covalent: how can you tell (3)
ionic compounds conduct when molten/ in liquid while covalent do not
ionic compounds tend to have high melting points as a lot of energy is required to break their strong ionic bonds in the lattice.
ionic compounds are usually water soluble
what is a type of bonding that is never found in elements
polar covalent
three types of bonding found in elements are
metallic
ldf
non polar covalent
is covalent bonding a van der waals force?
no
three types of van der waal forces
hydrogen bonding
ldf
pdpd interactions
does a catalyst provide energy
no
what three things does a catalyst do
lowers the activation energy that molecules need for successful collisions
provides an alternative route to the products
forms bonds with reacting molecules
Reminder: when Q asks for arrangement of amino acids in a peptide - the set does not have to be in order
when Q asks for arrangement of amino acids in a peptide - the set does not have to be in order
Reminder: when Q asks for a good solvent look for polar functional groups in given molecule. if it has any then look for most polar choice. if it doesn’t then look for least polar choice
when Q asks for a good solvent look for polar functional groups in given molecule. if it has any then look for most polar choice. if it doesn’t then look for least polar choice
For Q where substance A burnt to produce x energy + calc volume substance B to produce same x amount of energy. What is equation GIVEN: substance A: volume (burnt) energy (produced) substance B: volume (of 1g) energy (of 1g)
(A energy prod/ B energy of 1g) x B volume of 1g
