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 define the standard enthalpy of formation, including “1 mol” and “elements in their standard states”. (Guide: “What a standard enthalpy of formation is”)
- I can write the formation equation for a compound, using fractions where needed. (Practice Q2)
- I can explain why an element in its standard state has ΔH°f = 0, and name forms of elements that are not zero. (Guide; Practice Q1, Q6)
- I can explain why the formula works, using a detour through the elements. (Guide: Figure 1)
Calculation
- I can calculate ΔH° as ΣnΔH°f(products) − ΣnΔH°f(reactants), with every coefficient applied. (Guide: Worked examples 1 and 2; Practice Q3, Q4)
- I can choose the right value for the state shown, such as H₂O(l) or H₂O(g). (Guide: Worked example 2; Practice Q5)
- I can scale ΔH° to a given mass or amount of one substance. (Practice Q5)
- I can calculate ΔH° for a physical change, such as vaporising water or methanol. (Guide: “Physical processes too”; Practice Q6)
- I can work backwards from a known ΔH° to find one unknown ΔH°f. (Guide: Worked example 3; Practice Q6)
Reasoning
- I can use the sign of ΔH° to say whether a process is exothermic or endothermic. (Guide: Worked example 1; Practice Q4)
- I can describe an energy diagram with the elements at 0 and explain why a reaction between substances with positive ΔH°f can still be exothermic. (Practice Q7)
- I can explain why formation enthalpies give more accurate reaction enthalpies than bond enthalpies. (Guide: “Why we need a table of formation enthalpies”)
All ticked? Move on to Topic 6.9, Hess’s Law, or return to the course roadmap.