IGCSE›Oxford AQA IGCSE Chemistry›Mind mapsCalculating Rates of ReactionsOxford AQA IGCSE Chemistry: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsWhat is rate?How quickly reactants are used upOr how quickly products formFast reaction means a high rateCalculating rateRate = amount of reactant used ÷ timeRate = amount of product formed ÷ timeAmount in g, cm³ or mol/dm³Time usually in secondsWorked example12 cm³ of gas in 60 sMean rate = 12 ÷ 60Answer: 0.2 cm³/sRate of reactioncalculating ratesg/scm³/sReading graphsProduct or reactant on y-axis, time on xSteeper gradient means faster rateLine becomes less steep as reactants run outGraph goes flat when reaction finishesGradientsChord between two points gives mean rateTangent at a point gives instant rateGradient = change in y ÷ change in xExam tipsSteeper start means faster initial rateSame reactant amounts give the same final amountDraw a tangent for the rate at one instant