IB›IB Chemistry SL›Mind mapsR2.1 How much? The amount of chemical changeIB Chemistry SL: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsMoles methodEquation coefficients give the mole ratio1. Convert to moles2. Use the mole ratio3. Convert to the quantity askedn=m÷Mn = m \div Mn=m÷Mn=V÷Vmn = V \div V_mn=V÷Vm, with Vm=22.7 dm3 mol−1V_m = 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 dm³Divide cm³ by 1000Titration: moles of known, ratio, unknown concentration25.0 cm³ of 250.0 cm³ is one-tenthHydrate: x=(M−Manhydrous)÷18.02x = (M - M_{anhydrous}) \div 18.02x=(M−Manhydrous)÷18.02Limiting reactantCompletely used up, fixes the product amountOther reactant is in excessMoles ÷ coefficient: smallest is limitingMore excess does not raise theoretical yieldAmountmoles and yieldnMcVPercentage yieldyield=experimentaltheoretical×100\text{yield} = \frac{\text{experimental}}{\text{theoretical}} \times 100yield=theoreticalexperimental×100Below 100%: incomplete or reversible reactionsSide reactions and transfer losses lower itAbove 100%: product impure or wetAtom economyM(desired product)M(all reactants)×100\frac{M(\text{desired product})}{M(\text{all reactants})} \times 100M(all reactants)M(desired product)×100Key idea in green chemistryAddition reactions: 100%Glucose to ethanol: 51.2% as CO₂ formsEconomy from equation; yield from experimentExam tipsRound only the final answerKeep unrounded values in your calculatorDo not forget the scale-up from the titrated portion