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R2.2.10 HL

Rate-Concentration Graphs

How reaction rate varies with concentration for each order of reaction.

📘 IB Understanding

Sketch, identify and analyse graphical representations of zero, first and second order reactions from rate-concentration graphs.

Rate vs [A] for Different Orders

Rate-concentration graphs for zero, first, and second order reactions Zero Order [A] Rate Horizontal line Rate = k First Order [A] Rate Through origin Rate = k[A] Second Order [A] Rate Upward curve Rate = k[A]²

How to Read These Graphs

OrderGraph ShapeWhat It Means
ZeroHorizontal straight lineRate is constant regardless of [A]. The reactant is not in the RDS.
FirstStraight line through originRate is directly proportional to [A]. Gradient = k.
SecondUpward curve (parabola)Rate increases as the square of [A]. Doubling [A] quadruples the rate.

⚠️ Common Mistake

Students often confuse the zero-order concentration-time graph (a straight diagonal line going down) with the first-order rate-concentration graph (a straight diagonal line going up). Always check the axis labels before interpreting a graph!

← R2.2.9 [A]-Time GraphsR2.2.11 Half-Life →