IB›IB Chemistry HL›Mind mapsR2.1 How much? The amount of chemical changeIB Chemistry HL: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsMole method1. Convert to moles2. Use the mole ratio3. Convert to the quantity askedn=m÷Mn = m \div Mn=m÷MGases: n=V÷Vmn = V \div V_mn=V÷Vm, Vm=22.7 dm3 mol−1V_m = \mathbf{22.7}\,\text{dm}^3\text{ mol}^{-1}Vm=22.7dm3 mol−1 at STPSolutionsc=n÷Vc = n \div Vc=n÷V, with V in dm³cm³ ÷ 1000 gives dm³Titration: moles of known → ratio → unknown25.0 cm³ of 250.0 cm³ is one-tenthLimiting reactantCompletely used up, fixes the product amountMoles ÷ coefficient: smallest is limitingExtra excess reactant adds no productAmount of changemoles and yieldmolMMMcccdm³Percentage yieldexperimentaltheoretical×100\frac{\text{experimental}}{\text{theoretical}} \times 100theoreticalexperimental×100Below 100%: reversible, side reactions, lossesAbove 100% means impure or wet productAtom economyM(desired)M(all reactants)×100\frac{M(\text{desired})}{M(\text{all reactants})} \times 100M(all reactants)M(desired)×100Key idea in green chemistryAddition reactions: 100% atom economyComes from the equation; yield from the experimentExam tipsKeep unrounded values, round only the final answerGive sig figs matching the dataForgetting the scale-up from titrated portionWater of crystallisation: x=(M−Manhyd)÷18.02x = (M - M_{\text{anhyd}}) \div 18.02x=(M−Manhyd)÷18.02