A level OCR A chemistry Questions &
Correct Answers- Latest updated
Graded A+ Passed
rate of reaction
֎ -:- the change in concentration of a reactant or product per unit time
rate constant (k)
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֎ -:- The constant that links the rate of reaction with the concentrations of the
reactants raised to the powers of their orders in the rate equation.
half-life
֎ -:- The time taken for the concentration of the reactant to reduce by half
Benzene
֎ -:- a naturally occurring aromatic compound, which is a very stable planar ring
structure with delocalised electrons
Model
֎ -:- a simplified version that allows us to make predictions and understand
observations more easily
Lattice enthalpy
֎ -:- The enthalpy change that accompanies the formation of one mole of an
ionic lattice from its gaseous ions under standard conditions
e.g. K+(g) + Cl-(g) -> KCl(s)
- enthalpy change
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,standard enthalpy change of formation
֎ -:- The enthalpy change that takes place when one mole of a compound is
formed from its constituent elements in their standard states under standard
conditions.
e.g. K(s) + 1/2Cl2(g) -> KCl(s)
- enthalpy change
standard enthalpy change of atomisation
֎ -:- The enthalpy change that takes place when one mole of gaseous atoms
forms from the element in its standard state.
e.g. K(s) -> K(g)
+ enthalpy change
First electron affinity (opposite of first ionisation energy!)
֎ -:- The enthalpy change that takes place when one electron is added to each
atom in one mole of gaseous atoms to form one mole of gaseous 1- ions e.g. Cl(g) + e- ->
Cl-(g)
- 1st enthalpy change
+ 2nd enthalpy change as electron is repelled by 1- ion
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standard enthalpy change of solution
֎ -:- The enthalpy change that takes place when one mole of a solute is
completely dissolved in water under standard conditions
e.g. KCl(s) -> K+(aq) + Cl-(aq)
+ enthalpy change
standard enthalpy change of hydration
֎ -:- The enthalpy change that takes place when one mole of gaseous ions is
dissolved in water forming one mole of aqueous ions under standard
conditions
e.g. K+(g) -> K+(aq)
- enthalpy change
Entropy
֎ -:- a measure of the dispersal of energy in a system which is greater, the more
disordered a system
standard entropy
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Correct Answers- Latest updated
Graded A+ Passed
rate of reaction
֎ -:- the change in concentration of a reactant or product per unit time
rate constant (k)
26/08/2024 | © Copyright- This work may not be copied for profit.
, Excellenceiskey|2024/2025~Page|2
֎ -:- The constant that links the rate of reaction with the concentrations of the
reactants raised to the powers of their orders in the rate equation.
half-life
֎ -:- The time taken for the concentration of the reactant to reduce by half
Benzene
֎ -:- a naturally occurring aromatic compound, which is a very stable planar ring
structure with delocalised electrons
Model
֎ -:- a simplified version that allows us to make predictions and understand
observations more easily
Lattice enthalpy
֎ -:- The enthalpy change that accompanies the formation of one mole of an
ionic lattice from its gaseous ions under standard conditions
e.g. K+(g) + Cl-(g) -> KCl(s)
- enthalpy change
26/08/2024 | © Copyright- This work may not be copied for profit.
,standard enthalpy change of formation
֎ -:- The enthalpy change that takes place when one mole of a compound is
formed from its constituent elements in their standard states under standard
conditions.
e.g. K(s) + 1/2Cl2(g) -> KCl(s)
- enthalpy change
standard enthalpy change of atomisation
֎ -:- The enthalpy change that takes place when one mole of gaseous atoms
forms from the element in its standard state.
e.g. K(s) -> K(g)
+ enthalpy change
First electron affinity (opposite of first ionisation energy!)
֎ -:- The enthalpy change that takes place when one electron is added to each
atom in one mole of gaseous atoms to form one mole of gaseous 1- ions e.g. Cl(g) + e- ->
Cl-(g)
- 1st enthalpy change
+ 2nd enthalpy change as electron is repelled by 1- ion
26/08/2024 | © Copyright- This work may not be copied for profit.
, Excellenceiskey|2024/2025~Page|4
standard enthalpy change of solution
֎ -:- The enthalpy change that takes place when one mole of a solute is
completely dissolved in water under standard conditions
e.g. KCl(s) -> K+(aq) + Cl-(aq)
+ enthalpy change
standard enthalpy change of hydration
֎ -:- The enthalpy change that takes place when one mole of gaseous ions is
dissolved in water forming one mole of aqueous ions under standard
conditions
e.g. K+(g) -> K+(aq)
- enthalpy change
Entropy
֎ -:- a measure of the dispersal of energy in a system which is greater, the more
disordered a system
standard entropy
26/08/2024 | © Copyright- This work may not be copied for profit.
