Work through the list without notes. If you cannot do a statement, follow its link, then come back. Guide = study guide; Practice = practice questions.
Understanding
- I can explain what a standard molar entropy is and state its unit, J K⁻¹ mol⁻¹. (Guide: “Absolute entropy and standard molar entropy”)
- I can explain why entropy is called absolute and why every substance has a positive S° at 298 K. (Guide: “Absolute entropy and standard molar entropy”; Practice Q7(c))
- I can explain why elements in their standard states have S° above zero, unlike their ΔH°f values. (Practice Q6(d), Q7(c))
- I can describe how S° compares for the solid, liquid and gas of one substance, and why gases have the largest values. (Guide: Figure 1; Practice Q7(b))
Calculation
- I can calculate ΔS° for a reaction as products minus reactants, multiplying each S° by its coefficient. (Guide: Worked example 1; Practice Q1, Q2, Q6(b))
- I can choose the correct S° for each state, such as H₂O(l) rather than H₂O(g). (Practice Q3, Q4(b))
- I can calculate ΔS° for a physical change such as vaporisation. (Guide: Worked example 2; Practice Q7(a))
- I can convert ΔS° from J K⁻¹ mol⁻¹ to kJ K⁻¹ mol⁻¹. (Guide: Worked example 1(b); Practice Q3)
- I can scale ΔS° to a given mass by finding moles of reaction first. (Guide: Worked example 1(c); Practice Q4(c), Q6(c))
- I can work backwards from ΔS° to find an unknown S°. (Guide: Worked example 3; Practice Q5)
- I can write the new ΔS° when an equation is reversed or multiplied by a factor. (Revision notes: quick self-check)
Reasoning
- I can predict the sign of ΔS° from moles of gas and use it to check a calculated value. (Practice Q4(a), Q6(a))
- I can find the error in a calculation that gives a sign that contradicts the prediction, or a negative S°. (Practice Q5, Q6(d))
- I can explain a calculated ΔS° at the particle level. (Practice Q7(b))
All ticked? Move on to Topic 9.3, Gibbs Free Energy and Thermodynamic Favorability, or return to the course roadmap.