Hard Content Flashcards
What is an exothermic reaction?
One that gives off heat energy into the surrounding
What is an endothermic reaction?
One that takes in heat energy from the surroundings
What is the enthalpy change?
the overall energy change in a reaction?
What is the enthalpy change in an exothermic reaction?
negative because energy is given out
What is the enthalpy change in an endothermic reaction?
positive because energy is taken in
How can you calculate heat energy transferred?
mass of liquid being heated x shc x change in temp
how do you calculate molar enthalpy change?
molar enthalpy change = -energy transferred / moles
Why is bond breaking endothermic?
the energy used to break the bonds is greater that the energy released forming them
Why is making bonds exothermic?
the energy released making the bonds is greater than the energy used to make them
how can you calculate bond energies?
total energy absorbed to break bonds - total energy released to make bonds
what are two examples of reversible reactions?
copper sulfate + water -> hydrated copper sulfate
ammonia + hydrogen chloride -> ammonium chloride
what is equilibrium
the state of a chemical reaction in which the forward and reverse reactions are occurring at the same rate, but the concentrations of the reactants and products remain the same
If the equilibrium lies to the left?
mainly reactants, little products
if the equilibrium lies to the right?
mainly products, little reactants
reactant concentration is increased:
reaction forming products is favoured and equilibrium shifts
product concentration is favoured:
reaction forming reactants favoured and equilibrium shifts
temperature of reaction is increased (equilibrium):
endothermic reaction will be favoured
temperature of reaction is decreased (equilibrium):
exothermic reaction will be favoured
pressure of reaction is increased (equilibrium):
side of reaction with fewer gas moles favoured
pressure of reaction is decreased (equilibrium):
side of reaction with more gas moles faovured
what is ionic bonding?
the strong electrostatic attraction between positive an negative ions (metal and non metal)
When an ionic compound is formed….
electrons are transferred from a metal to the non metal to form positive and negative ions
carbonate:
Co3 2-
nitrate:
NO3 -
ammonium:
NH4 +
hydroxide:
OH-
sulphate:
SO4 2-
what is the boiling and melting point of ionic compounds and why?
high, giant ionic lattice, strong ionic bonding, lots of energy to overcome
do ionic compounds conduct electricity?
Yes molten or dissolved as there are mobile delocalised electrons, no as a solid.
why are ionic compounds brittle
when a lattice layer is hit, a layer of ions is shifted so that ions with the same charge are lined up together and they then repel eachother
what are covalent bonds?
the strong electrostatic connection between nuclei and a shared pair of electrons
what is the boiling point of simple covalent molecules?
low because they have strong covalent bonds but weak IMF which require little energy to overcome
do simple covalent structures conduct electricity?
no because the molecules are neutral and carry no charge
what is the boiling point of giant covalent substances?
high, giant covalent lattice, strong covalent bonds, lots of energy to break
what is the conductivity of graphite?
can conduct as it has mobile delocalised electrons
how can you calculate percentage yield?
(actual/calculated) x 100
what are three possible reasons for percentage yield being less than 100%
- reaction may be reversible
- side reactions may have occured
- products may be lost (i.e., time taken putting on bung)
what equation links gas moles, moles and volume?
moles = volume/24 dm3
what equation links moles, volume and concentration?
moles = conc x vol
electrode:
terminal at which electricity enters of leaves the electrode
anion:
a negatively charged particle
cation:
positively charged particle
cathode:
the negative electrode
anode:
positively charged electrode