Calculating Entropy Changes

If you stick some clean reactive metal, like magnesium, into an aqueous solution of hydrochloric acid... Hey presto! Bubbles of hydrogen gas! This gas production is a dead giveaway that the entropy of the system has increased.
But what if all the reactants and products are soluble in water and the entire chemical process occurs in aqueous solution. Has the entropy of the system increased or decreased?
Thankfully, chemists have a tool they can use to make quantitative predictions about the changes in entropy of a chemical system (ΔS). This tool is called the Standard Absolute Entropy (S°), and we have just added a new tutorial, game, test and exam to help you understand what this is and how it can be used.
AUS-e-TUTE Members should log-in to access the new resources under the heading "Thermodynamics".
If you are not already an AUS-e-TUTE there is a "free-to-view" tutorial currently available at https://www.ausetute.com.au/entropychange.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?
AUS-e-TUTE has just added a new tutorial, game, test and exam to help you understand what makes a reaction spontaneous, nonspontaneous, reversible or irreversible.
AUS-e-TUTE Members should log-in to use these new resources (listed under Thermodynamics in the Physical Chemistry section).

Not an AUS-e-TUTE Member?
A "free-to-view" spontaneous reactions tutorial is currently available for evaluation purposes at:
http://www.ausetute.com.au/spontaneous.html

Introduction to Entropy

What is entropy?
What is meant by a chemical system having low entropy or high entropy?
What is the relationship between disorder, energy and entropy?

If you are asking these questions, then you will find AUS-e-TUTE's new entropy introductory tutorial, game and test very helpful! AUS-e-TUTE Members should log in to use these new resources (under the topic heading Thermodynamics in the Test Centre).

Not an AUS-e-TUTE Member?
A "free-to-view" tutorial is currently available at http://www.ausetute.com.au/entropy.html