[ Visit http://www.wewwchemistry.com ] This example uses the Nernst equation to illustrate how changes in reactant or product concentration (effected by dilution) affect cell potentials.
DETERMINATION OF THE EQUILIBRIUM CONSTANT FOR THE FORMATION OF TRI-IODIDE IONAugustine Adu
A LABORATORY WORK THAT WILL HELP ANYONE TO DETERMINE EQUILIBRIUM CONSTANT OF TRI-IODIDE ION.
THE EQUILIBRIUM CONSTANT IS NOT DIRECTLY DETERMINED, THIS PIECE WILL GIVE A WAY TO HOW IT IS DONE.
Reference,
https://en.wikipedia.org/wiki/Term_symbol
James E. Huheey, Ellen A. Keiter, Richard L.Keiter and Okhil K. Medhi, Inorganic Chemistry, Principles of Structure and Reactivity. 4th Edn. Pearsons
DETERMINATION OF THE EQUILIBRIUM CONSTANT FOR THE FORMATION OF TRI-IODIDE IONAugustine Adu
A LABORATORY WORK THAT WILL HELP ANYONE TO DETERMINE EQUILIBRIUM CONSTANT OF TRI-IODIDE ION.
THE EQUILIBRIUM CONSTANT IS NOT DIRECTLY DETERMINED, THIS PIECE WILL GIVE A WAY TO HOW IT IS DONE.
Reference,
https://en.wikipedia.org/wiki/Term_symbol
James E. Huheey, Ellen A. Keiter, Richard L.Keiter and Okhil K. Medhi, Inorganic Chemistry, Principles of Structure and Reactivity. 4th Edn. Pearsons
I Hope You all like it very much. I wish it is beneficial for all of you and you can get enough knowledge from it. Clear and appropriate objectives, in terms of what the audience ought to feel, think, and do as a result of seeing the presentation. Objectives are realistic – and may be intermediate parts of a wider plan.
Nickel(II) reacts with dimethylglyoxime [C4H6(NOH)2] to form a coordination complex. The formation of the red chelate occurs quantitatively in an aqueous solution at pH 5 to 9. Usually, citric acid is added to lower the interference of iron
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I Hope You all like it very much. I wish it is beneficial for all of you and you can get enough knowledge from it. Clear and appropriate objectives, in terms of what the audience ought to feel, think, and do as a result of seeing the presentation. Objectives are realistic – and may be intermediate parts of a wider plan.
Nickel(II) reacts with dimethylglyoxime [C4H6(NOH)2] to form a coordination complex. The formation of the red chelate occurs quantitatively in an aqueous solution at pH 5 to 9. Usually, citric acid is added to lower the interference of iron
Solventless reaction in green chemistryAfrin Nirfa
Solventless reactions or solid state reactions are one of the principles involved in green chemistry. these reactions are more useful because the toxicity of solvents are reduced, easy to handle, cheaper and makes environment friendly.
ELECTROCHEMISTRY
Important Formula For 1 year B.E students and also using for the first year PG student using this Formulas we can able to Find the Emf of the solution
Like galvanized corrosion as well in physics we dont know to represent the chemical Cell
Summary of Content Changes to A Level H2 Chemistrywewwchemistry
[ www.wewwchemistry.com ]
This mind map is a summary of content changes made to the Advanced Level Chemistry syllabus jointly offered by the Singapore Examinations and Assessment Board (SEAB) and Cambridge International Examinations (CIE). It also compares the new Syllabus 9729 with the outgoing Syllabus 9647.
[ Related blog post: http://www.wewwchemistry.com/2014/06/chemistry-of-chromium ]
These slides briefly describe the chemistry of chromium within the scope of the Singapore-Cambridge GCE A Level 9647 H2 Chemistry syllabus. Topics include the unusual electronic configuration of chromium, the various oxidation states of chromium and the reactions of common chromium compounds like chromium(III) chloride, chromium(III) nitrate, chromium(III) hydroxide,potassium chromate(VI) and potassium dichromate(VI).
[ Related blog post: http://www.wewwchemistry.com/2013/08/graphs-showing-effect-of-changing-conditions-on-equilibrium ] This file was updated on 15 Aug 2013. Minor changes were made to Slides 12 and 15. More substantial changes were made to Slides 26 to 45, primarily to modify the concentration-time graphs so that these were consistent with those I used in my detailed explanation on the effect of changing conditions on an equilibrium system.
~~~~~~~~~~~~~~~~~~~~
This is a summary of Chemical Equilibria, prepared according to the Singapore-Cambridge GCE A Level 9647 H2 Chemistry syllabus. It covers the differences between reversible and irreversible reactions, and explains the equilibrium state. Factors affecting equilibrium system, as applied to the Haber process, are also included.
Reactions Involving Alkanes, Alkenes and Areneswewwchemistry
[ Visit http://www.wewwchemistry.com ] This is a summary of reactions involving hydrocarbons, prepared according to the Singapore-Cambridge GCE A Level 9647 H2 Chemistry syllabus. Free-radical substitution mechanism of alkanes, electrophilic addition of alkenes and electrophilic (aromatic) substitution of arenes are covered. A brief discussion on the aromaticity of the benzene ring, and examples of activating and deactivating substituent groups are also included.
Hybridisation of Carbon Atomic Orbitalswewwchemistry
[ Visit http://www.wewwchemistry.com ] This set of Powerpoint slides introduces students to the basic concepts of Hybridisation Theory as applied to the atomic orbitals of carbon. sp3 hybridisation as in methane, sp2 hybridisation as in ethene, and sp hybridisation as in ethyne, are illustrated.
[ Visit http://www.wewwchemistry.com ] This is a summary presentation of the introductory topics in Organic Chemistry, prepared according to the Singapore-Cambridge GCE A Level 9647 H2 Chemistry syllabus.
[ Visit http://www.wewwchemistry.com ] This example shows how the pH of a buffer may be calculated. An acidic buffer containing ethanoic acid and ethanoate ions is used. Two methods are shown: the first requires the construction of the ICE table, while the second involves direct substitution of given data into the Henderson-Hasselbalch equation.
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1. I The Nernst Equation
Reported cell potentials are typically measured under standard conditions:
Solutes in aqueous solutions have a concentration of 1.0 mol dm–3
Gaseous reactants or products have a pressure of 1 atm
Measurements are taken at 298 K
Galvanic cells seldom operate under standard conditions. Ecell measured under non-
standard conditions is not equal to (E— )cell, the cell potential measured under
o
standard conditions.
http://www.wewwchemistry.com Page 1
2. It has been determined that cell potentials are related to concentrations of reactants
and products, and to temperature via the Nernst equation, as follows:
Ecell = (E— )cell – ⎜ RT ⎟ ln Q
o ⎛ ⎞
⎜ nF ⎟
⎝ ⎠
where R is the gas constant (8.31 J K–1 mol–1)
T is the temperature (K)
€
n is the number of moles of electrons
transferred between oxidising and reducing
agents
F is the Faraday’s constant (96500 C mol–1)
Q is the reaction quotient, which is based on
the cell reaction
This equation gives the Ecell measured under non-standard conditions.
The Nernst equation is sometimes expressed in terms of base 10 logarithm. For a
cell at 298 K, the above equation becomes:
Ecell = (E— )cell – ⎜ 0.0592 ⎟ log10 Q
o ⎛ ⎞
⎜
⎝ n ⎟⎠
http://www.wewwchemistry.com Page 2
€
3. II Using the Nernst Equation to Illustrate the Effect of Dilution on (E— )cell
o
Consider the following galvanic cell set up at 298 K:
Al(s) | Al3+(aq) || Ni2+(aq) | Ni(s)
Anode : Al(s) → Al3+(aq) + 3e–
Cathode : Ni2+(aq) + 2e– → Ni(s)
Overall cell reaction : 2Al(s) + 3Ni2+(aq) → 2Al3+(aq) + 3Ni(s)
Under standard conditions, [Al3+] and [Ni2+] are both 1.00 mol dm–3,
(E— )cell = (E— )reduction – (E— )oxidation
o o o
= –0.25 – (–1.66)
= +1.41 V
http://www.wewwchemistry.com Page 3
4. Scenario 1:
How does (E— )cell change when water is added to the Ni2+/Ni half cell such that [Ni2+]
o
is decreased ten times? (All measurements are taken at 298 K.)
— )cell – ⎛ 0.0592 ⎞ log10 Q
o
Ecell = (E ⎜
⎜ n ⎟
⎟
⎝ ⎠
3+ 2
+1.41 – ⎜ 0.0592 ⎟ log10 [Al ]
⎛ ⎞
= 6 ⎟
€
⎜
⎝ ⎠ [Ni2+ ]3
+1.41 – ⎜ 0.0592 ⎟ log10 1
⎛ ⎞
=
⎜ 6 ⎟ ⎞3
⎜ 1 ⎟
⎝ ⎠ ⎛
€ €
⎜ 10 ⎟
⎝ ⎠
= +1.41 – 0.0296
€
= +1.38 V €
Note:
Six electrons are tranferred during the oxidation of Al and the reduction Ni2+.
Thus, n = 6.
(Q > 1) Ecell decreases.
http://www.wewwchemistry.com Page 4
5. Scenario 2:
How does (E— )cell change when water is added to the Al3+/Al half cell such that [Al3+]
o
is decreased ten times? (All measurements are taken at 298 K.)
— )cell – ⎛ 0.0592 ⎞ log10 Q
o
Ecell = (E ⎜
⎜ n ⎟
⎟
⎝ ⎠
3+ 2
+1.41 – ⎜ 0.0592 ⎟ log10 [Al ]
⎛ ⎞
= 6 ⎟
€
⎜
⎝ ⎠ [Ni2+ ]3
2
⎛
⎜ 1 ⎞
⎟
= € 0.0592 ⎞ €
⎛ ⎜ 10 ⎟
+1.41 – ⎜ ⎟ log10 ⎝ ⎠
⎜
⎝6 ⎟⎠ 1
= +1.41 – (–0.0197)
= +1.43 V
€ €
(Q < 1) Ecell increases.
http://www.wewwchemistry.com Page 5
6. Scenario 3:
How does (E— )cell change when water is added to both half cells such that [Al3+] and
o
[Ni2+] are each decreased by ten times? (All measurements are taken at 298 K.)
— )cell – ⎛ 0.0592 ⎞ log10 Q
o
Ecell = (E ⎜
⎜ n ⎟
⎟
⎝ ⎠
3+ 2
+1.41 – ⎜ 0.0592 ⎟ log10 [Al ]
⎛ ⎞
= 6 ⎟
€
⎜
⎝ ⎠ [Ni2+ ]3
2
⎛
⎜ 1 ⎞
⎟
€ 0.0592 ⎞ €
⎛ ⎜ 10 ⎟
= +1.41 – ⎟ log10
⎜ ⎝ ⎠
6 ⎟
⎜
⎝ ⎠ ⎛
1 ⎞
3
⎜ ⎟
⎜ 10 ⎟
⎝ ⎠
= +1.41 – 0.00987
€
= +1.40 V €
(Resulting Q > 1) Ecell decreases, albeit slightly.
http://www.wewwchemistry.com Page 6
7. Conclusion
In general, any change to the cell that increases Q decreases Ecell, while any change
that decreases Q will increase Ecell. Thus, adding reactant or removing product
increases Ecell. while removing reactant or adding product decreases Ecell.
In the above example,
when reactant concentration ([Ni2+]) is smaller than 1 mol dm–3, Ecell is less than
(E— )cell (Scenario 1).
o
when product concentration ([Al3+]) is smaller than 1 mol dm–3, Ecell is more than
(E— )cell (Scenario 2).
o
If concentrations of both products and reactants are decreased in the cell, whether
Ecell is more or less than (E— )cell depends on the resulting Q:
o
Q > 1, Ecell is less than (E— )cell (Scenario 3)
o
Q = 1, there is no change to (E— )cell, i.e. Ecell = (E— )cell
o o
Q < 1, Ecell is more than (E— )cell
o
http://www.wewwchemistry.com Page 7