How to know what species will spontaneously react in redox reactions

A redox reaction is spontaneous if the standard electrode potential is positive,
that is,
if E^o_(reaction) > 0

Find out more, and look at a worked example, at: https://www.ausetute.com.au/redoxspon.html

Gibbs Free Energy of Formation

You can use standard enthalpy change (ΔH°) and standard absolute entropy (S°) data to calculate the change in Gibbs free energy (ΔG°) for a chemical reaction or physical change using the equation:

 ΔG° = ΔH° - TΔS°

... OR ....
you can use tables of values for the standard Gibbs free energy of formation of compounds (ΔG_ƒ°).
For a chemical reaction or physical change:

reactants → products 

ΔG° = ΣΔG_ƒ°(products) - ΣΔG_ƒ°(reactants)

If you would like to understand where this comes from and how it can be applied solve problems in chemistry, visit our new tutorial Standard Gibbs Free Energy of Formation Calculations

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Effect of Temperature on GIbbs Free Energy

Imagine a reaction in which you decompose liquid water to produce oxygen gas and hydrogen gas:

H₂O_(l) → H_2(g) + ½O_2(g)

The reaction is endothermic, ΔH > 0, and the change in entropy is also positive, ΔS > 0
At room temperature and pressure this reaction is not spontaneous ( ΔG > 0).
But could I heat, or cool, the reaction sufficiently to make the reaction spontaneous?
Can I turn a nonspontaneous reaction into a spontaneous reaction by changing the temperature?
Want to know?
Go to https://www.ausetute.com.au/gibbstemp.html

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Gibbs Free Energy and Spontaneity of Reactions

Whether or not a chemical reaction proceeds in a particular direction depends on a balance between the enthalpy of the system and its entropy.
Gibbs Free Energy allows us to quantify this relationship, and determine whether a particular reaction will be spontaneous.
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There is a "free-to-view" tutorial currently available at http://www.ausetute.com.au/freeenergy.html

Spontaneous Chemical Reactions

What makes a chemical reaction spontaneous?
If I add hydrochloric acid (HCl_(aq)) to metallic magnesium (Mg_(s)), bubbles of hydrogen gas (H_2(g)) are given off and the remaining solution contains chloride ions and magnesium ions (MgCl_2(aq)):

Mg_(s) + 2HCl_(aq) → H_2(g) + MgCl_2(aq)

But if I try to bubble hydrogen gas through an aqueous solution of magnesium chloride, nothing happens. No solid magnesium forms! Why?
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A "free-to-view" spontaneous reactions tutorial is currently available for evaluation purposes at:
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