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This module extends the study of energy, reaction rates and equilibria, and the periodic table. The main areas of physical chemistry studied include: • rate equations, orders of reaction, the rate determining step • equilibrium constants, Kc and Kp • acid–base equilibria including pH, Ka and buffer solutions • lattice enthalpy and Born–Haber cycles • entropy and free energy • electrochemical cells. The main areas of inorganic chemistry studied include: • redox chemistry • transition elements.
Zero Order Reactions
What is the shape of the concentration-time graph?
What is the shape of the rate-concentration graph?
negative straight line / horizontal line
First Order Reactions
What is the shape of the concentration-time graph?
What is the shape of the rate-concentration graph?
negative curve with decreasing gradient / positive straight line through origin
Second Order Reactions
What is the shape of the concentration-time graph?
What is the shape of the rate-concentration graph?
negative curve with decreasing gradient / positive curve with increasing gradient
What are the 2 methods for determining the rate constant from a concentration-time graph for a first order reaction?
tangent gradient / half life
In the Arrhenius equation, what does the exponential factor represent?
proportion of molecules that exceed Ea
The Arrhenius Equation - A: _______________________ (Frequency Factor)
Takes into account _________________________________.
This term does increase slightly with __________________ as the frequency of collisions increases but it is essentially _______________ over a small range of this.
Essentially gives the rate if _________________________.
pre-exponential term / frequency of collisions with correct orientation / temperature / constant / no Ea
What is the Arrhenius plot equation? (1→6)
ln K / - Ea / R / 1 / T / ln A
How do you determine Ea from the Arrhenius plot?
- R X gradient
How do you determine A (pre-exponential / frequency factor) from the Arrhenius plot?
find ln A from intercept then use exp
How do you work out partial pressure of A?
mole fraction of A X total pressure
How do you work out mole fraction of A?
number of moles of A / total number of moles in gas mixture
Equilibrium Constants
What does K < 1 indicate about the position of equilibrium?
What does K = 1 indicate about the position of equilibrium?
What does K > 1 indicate about the position of equilibrium?
favours reactants / halfway / favours products
What does a conjugate acid-base pair contain?
2 species that can be interconverted by proton transfer
What do the terms monobasic, dibasic & tribasic acids refer to?
total number of H+ in acid that can be replaced per molecule in acid-base reactions
The Stronger the Acid…
The ______________ the Ka value.
The ______________ the pKa value.
larger / smaller
The Weaker the Acid…
The ______________ the Ka value.
The ______________ the pKa value.
smaller / larger
How do you work out the concentration of H+ of weak acids?
root (Ka X [HA])
What is Kw called?
ionic product of water
What is lattice enthalpy?
1 mole ionic compound formed from gaseous ions
In Born-Haber cycles, what processes does route 1 require?
gaseous atom formation / gaseous ion formation / lattice formation
In Born-Haber cycles, what happens in route 2? What enthalpy change occurs?
elements converted in standard states directly to ionic lattice / formation
Born-Haber Cycles - Route 1
Formation of gaseous atoms - changing the elements in their standard states into gaseous atoms. Endothermic as it involves __________________.
Formation of gaseous ions - changing the gaseous atoms into positive and negative gaseous ions. Overall, this change is _______________.
Lattice formation - changing the gaseous ions into the solid ionic lattice. This is the lattice enthalpy and is ______________.
bond breaking / endothermic / exothermic
What is the enthalpy change of solution?
1 mole solute dissolves in solvent
The Dissolving Process
When a solid ionic compound dissolves in water, two processes take place: ________________________ & ____________________________.
Two types of energy change are involved.
The ionic lattice is broken up forming separate gaseous ions.
This is the opposite energy change from lattice energy, which forms the ___________________ from gaseous ions.
Enthalpy change of __________________: the separate gaseous ions interact with polar water molecules to form ______________________.
ionic lattice breaks up / water molecules attracted to & surround ions / ionic lattice / hydration / hydrated aqueous ions
How does increased cation size affect lattice enthalpy?
ionic radius increases / attraction between ions decreases / lattice energy less negative / mp decreases
How does increased ionic charge affect lattice enthalpy?
attraction between ions increases / lattice energy more negative / mp increases
How does increased cation size affect hydration enthalpy?
ionic radius increases / ion-water attraction decreases / hydration energy less negative
How does increased ionic charge affect hydration enthalpy?
attraction with water increases / hydration energy more negative
How can the entropy change of a reaction be calculated?
products’ standard entropy - reactants’ standard entropy
What is the Gibbs’ equation?
free energy change = enthalpy change with surroundings - (temperature in K X system entropy change)
When is thermodynamic feasibiity supported?
enthalpy change with surroundings negative / system entropy change positive
In an Operating Cell…
What occurs to the electrode with the more reactive metal? Which electrode is this?
What occurs to the electrode with the less reactive metal? Which electrode is this?
oxidised / negative / reduced / positive
What Tendency is Increased by a Standard Electrode Potential that is…
More negative?
Which reactivity is greater in transferring electrons?
More positive?
Which reactivity is greater in transferring electrons?
oxidation / metal / reduction / non-metal
How are standard cell potentials calculated?
positive electrode standard cell potential - negative electrode standard cell potential
Note
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