Chemistry Study Guide
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Practice calculating Activation Energy
The following table gives the variation of the rate constant with temperature for the first-order reaction: 2N2O5 (g) 2N2O4 + O2 (g).
T (K)
|
k (s-1)
|
273
|
9.89x103
|
298
|
2.20x105
|
318
|
6.58x106
|
338
|
3.98x107
|
Determine graphically the activation energy (Ea) for the reaction.
Practice with Half life
A solution that is 5.2x10-8 M in 32P is stored in a metal container for 100 days.
1. Plot the decay in the concentration of 32P as a function of time. The half life of
32P is 14.3 days.
2. Plot ln[32P] as a function of time.
3. Show on both plots when the [32P] is 50%, 75% and 90% of its original value.
4. Show how you could use the plot of the natural log to obtain the rate constant
and the half life of the radioisotope if you measured the concentration of the
isotope as a function of time.
Practice determining half reactions
Write out the redox half reactions for the following:
- Sn (s) + Ag(NO3) (aq) Sn(NO3)2 (aq) + Ag (s)
- Cu(SO4) (aq) + Zn (S) Cu (s) + Zn(SO4) (aq)
Balance the following redox reactions:
- Cl- (aq) + Cr2O72- (aq) → Cl2 (g) + Cr3+ (aq)
- Fe3+ (aq) + Cr2O72- (aq) → Fe2+ (aq) + Cr2+ (aq)
Practice determining the rate Law
The reaction 2NO + O2 → 2NO2 is believed to occur by the following mechanism:
2NO N2O2 FAST (rate constants k1 and k2)
N2O2 + O2 → 2NO SLOW ( rate constant, k2)
What is the rate law for this reaction? Use the steady state approximation.
Practicing Electrochemistry
Voltaic Cell (Galvanic or Electrochemical Cell)
A voltaic cell is assembled with Sn(s) and Sn(NO3)2 (aq) in one compartment and Ag(s) and AgNO3 (aq) in the other. An external wire connects the two electrodes and a salt bridge containing KNO3 connects the two solutions.
- In the product favored reaction, Ag+ is reduced to silver metal. Write out the balance net ionic equation for this reaction.
- Which half reaction occurs at the anode?
- Which half reaction occurs at the cathode?
- Write the balanced cell reaction and calculate the standard cell potential.
- Draw a diagram of the cell, indicating the direction of electron flow outside the cell and the direction of ion flow within the cell (across the salt bridge).
Practicing Electrochemistry Again
A battery can be made from aluminum metal and chlorine gas.
- Write a balanced equation for the reaction that would occur in a battery using the following half reactions:
Al3+ (aq)/ Al (s)
Cl2 (g)/ Cl- (aq)
- Which half reaction occurs at the anode and which occurs at the cathode?
- Calculate the standard potential (Eº cell) for the battery.
- Calculate Gº for this reaction.
Practicing Electroplating
How many grams of Iron metal are produced when a current of 10A is passed through a solution of Iron (III) Nitrate for 45 minutes?
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