# CH0002 - Lecture 3

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1. Another Gibbs free energy equation using the Equilibrium constant
ΔGo = -RT lnK
2. Thermodynamics tell us whether or not a reaction is ... and ... but it cannot tell us ...
• ...spontaneous
• ...how far the reaction will go
• ...how fast it will be
3. What does Kinetics tell us?
• How quickly a reaction will take place.
• i.e. the rate of reaction.
4. What is the rate?
Rate = Change in concentration / Time
5. What can you use to measure the concentration?
• Volumetric methods - Change in volume of gas or increase in pressure
• Gravimetric methods - Change in mass (if a gas is consumed or evolved by the reaction)
• Instrumental methods -  Change in physical property which correlates with concentration. e.g colour, electrical conductivity, pH
6. For a reaction
aA + bB --> cC + eE
What is the rate?
• rate =
• -1/d[A]/dt   =
• -1/b x d[B]/dt   =
• +1/c x d[C]/dt   =
• +1/e x d[E]/dt

• Where t = time
• Where d = change in
7. The rate quation for a chemical reaction shows...
...how the rate depends on the concentrations of the various reactants and products
8. What is the rate equation?
rate = d[A]/dt = -k[A]n

Where is the rate constant and n is the reaction order.

The minus sign indicates that the concentration of A falls with time. i.e. it is a reactant not a product
9. In the rate equation, what do the powers to which the concentrations are raised indicate?
The individual orders of reaction.
10. Rate = (with powers)
Rate = k[A]x[B]y[C]z
11. Total order of reaction is given by...
sum of the individual orders.

Total order = x+y+z
12. First order Units
• Rate = k[A]1
• Mol dm-3s-1 = k(mol dm-3)1
• s-1 = k
13. Second order units
• Rate = k[A]2
• Mol dm-3s-1 = k(mol dm-3)2
• dm3mol-1s-1 = k

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 Author: james14hunter ID: 260335 Filename: CH0002 - Lecture 3 Updated: 2014-02-05 10:45:39 Tags: CH0002 Lecture Folders: CH0002 - Lecture 3 Description: CH0002 - Lecture 3 Show Answers:

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