Covers the various sections relating to Rates of Reactions, as per the IEB Physical Sciences SAG.
Includes notes from the textbook, as well as additional class, video and research information, diagrams and practice questions.
Applicable to all IEB Grade 12s.
Written by a 95% < student.
Collisions:
When 2 reactance particles collide a reaction does not always occur
Ek1 Ek2
Collision
Kinetic energy:
If Ek1 + Ek2 ≥ Ea than a successful collision, a reaction takes place, could occur.
If Ek1 + Ek2 < Ea than a successful collision, no reaction, will occur.
Orientation:
Must collide so that the functional group, or centres of chemical activity, are in contact.
Collision theory
= Colliding molecules must have, apart from the correct orientation, a kinetic energy equal to or
bigger than the activation energy of a reaction before the reaction can take place.
,Rate of reaction
The change in concentration per unit time of either a reactant or a product.
𝐶ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 ∆𝑐
Rate = 𝑇𝑜𝑡𝑎𝑙 𝑡𝑖𝑚𝑒 𝑡𝑎𝑘𝑒𝑛
= ∆𝑡
Factors that affect reaction rate:
Nature of the reacting substances, but we cannot alter this, so rarely asked.
To increase reaction rate:
1. Increase the temperature
2. Add a catalyst at the start
3. Gas: Increase the pressure
4. Liquid or solution: Increase the concentration
5. Solid: Increase the surface area, by breaking into smaller pieces
, Measuring rates and graphs
The gradient of the tangent to the curve is used to determine rate.
∆𝑉 𝑜𝑟 ∆𝑐 𝑜𝑟 ∆𝑚
Gradient = ∆𝑡
= rate of reaction
Graphs:
Graph 1: Using products
e.g. Volume of gas formed (ml)
Time (s)
Graph 2: Using reactants
e.g. Mass of flask (g)
Time (s)
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