Reaction Progress and Rate
Measure and interpret reaction progress, calculate average rates with units, and explain the effects of temperature, concentration, particle size and catalysts.
How to study National 5 Chemistry
Move between particle explanations, formulae, calculations, experimental evidence and justified conclusions, while using official materials for exact written-paper and assignment practice.
Core concepts
Concept 1
Reaction progress can be followed through a measurable change such as mass, gas volume or another relevant quantity.
Exam cue: State exactly which quantity changes and include both quantity and time units in a rate.
Concept 2
A progress graph can show the end-point, quantity of product, quantity of reactant used and effects of changing conditions.
Exam cue: Read a graph interval before calculating rather than using the whole reaction automatically.
Concept 3
Average rate is change in quantity divided by change in time; increasing temperature, concentration or surface area and adding a catalyst can increase rate.
Exam cue: Separate a faster rate from a larger final yield; the graph evidence may show one without the other.
Risk pitfalls and guardrails
Treating the steepest graph as proof that it produces more product.
Guardrail: Check formulae, charges, units, state or experimental conditions before committing to the final conclusion.
Forgetting to convert the chosen graph interval into a change in quantity.
Guardrail: Check formulae, charges, units, state or experimental conditions before committing to the final conclusion.
Saying that a catalyst is used up or changes the final quantity of product.
Guardrail: Check formulae, charges, units, state or experimental conditions before committing to the final conclusion.
Memory anchors
Average rate
Average rate equals change in a measured quantity divided by change in time.
Graph gradient
A steeper progress graph represents a faster rate over that interval.
Reaction end-point
The reaction has reached its end-point when the measured quantity stops changing.
Surface area
Smaller particles expose a greater total surface area and usually react faster.
Concentration
A higher reactant concentration can increase the frequency of successful collisions.
Catalyst
A catalyst speeds a reaction and can be recovered chemically unchanged.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
A reaction produces 48 cm³ of gas in 60 s. What is its average rate of gas production?
During a reaction, the mass of a flask falls from 126.8 g to 124.4 g in 80 s. What is the average rate of mass loss?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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