enthalpy and entropy
暂无描述。系统推荐的高质量记忆内容，适合每天坚持背诵学习。
卡片预览 (8 张)
What is entropy?
A measure of the dispersal of energy in a system OR how disordered something is.
What is a spontaneous process?
A process that proceeds on its own without external influence (so no continuous energy supply). Eg, diffusion.
Why can some endothermic reactions still be feasible?
As these substances become more energetically stable when there is disorder.
When is a substance thermodynamically stable?
When it reaches its maximum entropy state (lowest energy state).
How is entropy change (ΔS⦵) calculated? What is it measured in? And what does it being +ve and -ve mean?
● ΔS⦵ = ΣS⦵products - ΣS⦵reactants ● Measured in JK-1mol-1 ● +ve means increase in disorder/entropy. ● -ve means decrease in disorder/entropy. S⦵ alone is the entropy per molecule which is always positive.
What is the Gibbs free energy equation? What are the outcomes
ΔG = ΔH - TΔS ΔG < 0 ⇒ feasible (more negative ⇒ more feasible). ● ΔG = 0 ⇒ equilibrium (this is similar for a puddle in equilibrium). ● ΔG > 0 ⇒ not feasible. Note that ΔS can be in JK-1mol-1 rather than kJK-1mol-1.
When is Gibbs free energy not useful
While a reaction may be feasible, it can still… ● Have a very high activation energy. ● Be incredibly slow that you won’t it happening at all.
How can Gibbs free energy be plotted? What does the gradient tell you?
● Plot the ΔG v T of ΔG = ΔH - TΔS as y = mx + c. ● The gradient tells you the entropy change. You can see when a reaction becomes feasible under this.