. Which phase changes result in ΔS < 0? 2. Which selection of coefficients properly balances the redox equation in an acidic solution: ____H+(aq) + ____ ClO2-(aq) → ___ Cl2(g) + ___ H2O (l)? 3. Determine the number of water molecules necessary to balance the following chemical equation before the H’s would be balanced. Cr2O72-(aq) + 2Cl-(aq) → 2Cr3+(aq) + Cl2(g) + ________ H2O(l)
Science behind corrosion-test
Corrosion is defined as an activity that transforms refined metals into more chemically stable forms such as oxide, hydroxide, carbonate, or sulfide. It refers to the slow decomposition of things (typically metals); thanks to chemical and/or electrochemical reactions with their surroundings. Corrosion engineering is the science of preventing and controlling corrosion.
Corrosion
Corrosion is defined as an activity that transforms refined metals into more chemically stable forms such as oxide, hydroxide, carbonate, or sulfide. It refers to the slow decomposition of things (typically metals); thanks to chemical and/or electrochemical reactions with their surroundings. Corrosion engineering is the science of preventing and controlling corrosion.
1. Which phase changes result in ΔS < 0?
2. Which selection of coefficients properly balances the redox equation in an acidic solution:
____H+(aq) + ____ ClO2-(aq) → ___ Cl2(g) + ___ H2O (l)?
3. Determine the number of water molecules necessary to balance the following chemical equation before the H’s would be balanced.
Cr2O72-(aq) + 2Cl-(aq) → 2Cr3+(aq) + Cl2(g) + ________ H2O(l)
4.For a galvanic cell, the cathode has a ________ sign and is the site of ________.
5.During an
6.Sodium reacts violently with water according to the equation:
2 Na(s) + 2 H2O(l) → 2 NaOH(aq) + H2(g)
The resulting solution has a higher temperature than the water prior to the addition of sodium. What are the signs of ΔH° and ΔS° for this reaction?
7.Calculate ΔS° for the following reaction.
N2(g) + 2 O2(g) → 2 NO2(g)
|
Species |
So, J/(K mol) |
|
N2 (g) |
191.5 |
|
O2 (g) |
205.0 |
|
NO2 (g) |
240.0 |
8.Using the following standard reduction potentials:
|
Fe3+(aq) + e- → Fe2+(aq) E° = +0.77 V |
|
Pb2+(aq) + 2 e- → Pb(s) E° = -0.13 V |
calculate the standard cell potential for the galvanic cell reaction given below, and determine whether or not this reaction is spontaneous under standard conditions.
Pb2+(aq) + 2 Fe2+(aq) → 2 Fe3+(aq) + Pb(s)
9.
Consider the reaction:
N2(g) + 3 F2(g) → 2 NF3(g) ΔH° = -249 kJ and ΔS° = -278 J/K at 25°C
Calculate ΔG° and state whether the equilibrium composition should favor reactants or products at standard conditions.
10.
Calculate the standard free energy for the reaction given.
2 CH3OH(l) + 3 O2(g) → 2 CO2(g) + 4 H2O(l)
|
Species |
ΔGof (kJ/mol) |
|
CH3OH (l) |
-166.4 |
|
O2 (g) |
0.0 |
|
CO2 (g) |
-394.4 |
|
H2O (l) |
-237.3 |
11.If ΔG° is positive (+) for a reaction, then
12.
Which of the following terms can be used to describe an
I. an electrolytic cell
II. a galvanic cell
III. a voltaic cell
13.Which cell involves a non-spontaneous
14.
The nickel-cadmium battery cell has a standard potential of +1.20 V. The cell reaction is
2 NiO(OH)(s) + Cd(s) + 2 H2O(l) → 2 Ni(OH)2(s) + Cd(OH)2(s).
|
Half reactions: |
|
Cd(s) ------> Cd2+ (aq) + 2 e- |
|
2Ni3+ (aq) + 2e- -----> 2Ni2+ (aq)
|
What is the standard free energy change for this reaction? [ΔGo = -nFEocell]
15.During an electrochemical reaction, electrons move through the external circuit toward the ________ and positive ions in the cell move toward the ________.
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