From: Andrew Lorimer <andrew@lorimer.id.au>
Date: Sun, 3 Mar 2019 08:21:40 +0000 (+1100)
Subject: electrochemical series and galvanic cells
X-Git-Tag: yr12~228
X-Git-Url: https://git.lorimer.id.au/notes.git/diff_plain/c78bf500ad582fe6b02a531f9df7090e86fe89ee?ds=inline;hp=62aa2fae7b0fd1d5f01ddcd813caec3a018b38de

electrochemical series and galvanic cells
---

diff --git a/chem/electrochemistry.md b/chem/electrochemistry.md
index 2d465e2..20de01e 100644
--- a/chem/electrochemistry.md
+++ b/chem/electrochemistry.md
@@ -1,16 +1,11 @@
----
-header-includes:
-- \usepackage[version=4]{mhchem}
----
-
 # Electrochemistry
 
 ## Oxidation states
 
 Indicates charge (ionisation) of an element
 
-**Oxidation** - loss of e-  
-**Reduction** - gain of e-
+**Oxidation** - loss of e- (at anode)  
+**Reduction** - gain of e- (at cathode)
 
 Main group elements (i.e. group 2) - generally one oxidation state:
 
@@ -26,15 +21,14 @@ Main group elements (i.e. group 2) - generally one oxidation state:
 
 Transition metals (d shell) may have several oxidation states.
 
-$$\ce{H_2}$$
-
 Common oxidation numbers:
 
-| elements          | common ox. no. in compounds | exceptions          |
-| ----------------- | --------------------------- | ------------------- |
-| main group metals | valency                     | no                  |
-| hydrogen          | +1                          | metal hydrides (-1) |
-| oxygen            | -2                          |
+| elements          | common ox. state | exceptions          |
+| ----------------- | ---------------- | ------------------- |
+| main group metals | valency          |                     |
+| hydrogen          | +1               | metal hydrides (-1) |
+| oxygen            | -2               | ce{H2O2} (-1)       |
+| halogens          | -1               |                     |
 
 
 ### Rules for oxidation states
@@ -44,3 +38,29 @@ Common oxidation numbers:
 - oxidation number of simple ion is the charge of the ion
 - sum of oxidation numbers in polyatomic ion is the charge of the ion
 - sum of oxidation numbers of a neutral compound is zero
+
+## Electrochemical series
+
+- Top is most likely to be reduced
+- Strongest reductants are bottom right
+- Strongest oxidants are top left
+- Strong oxidants have weak conjugate reductants
+- $E^0$ values are measured relative to ce{H2} / ce{H^+} = 0V
+
+## Conjugate redox pairs
+
+Oxidant and conjugate *reduced form*  
+e.g. ce{Cu^2+} / ce{Cu}, $\quad$ ce{Zn^2+} / ce{Zn}
+
+Usually one member of pair is used as electrode (except for *inert electrodes*, e.g. platinum)
+
+## Electrochemical/galvanic cells
+
+1. Find two half reactions involved (between electrode and solution)
+2. Higher equation will proceed left to right
+3. Lower equation will proceed right to left
+
+emf for each cell is calculated as $E^0(\text{red}) - E^0(\text{ox})$  
+Then total emf is $\sum_{i=1}^2 \Sigma E^0({i})$
+
+For a spontaneous reaction to occur, species on left must be in electrical contact with species on lower right
\ No newline at end of file