Rate of reaction Flashcards
How can we interpret graphs?
End point of a reaction
Quantity of product
Quantity of reactant used
Effect of changing conditions
How can we follow the progress of chemical reactions?
Changes in mass, volume and other quantities
How can ROR be increased?
Increasing temp
Increasing concentration of a reactant
Increasing surface area/decreasing particle size
Use of a catalyst
What are catalysts?
Substances used to speed up chemical reactions but can be recovered chemically unchanged at the end of the reaction
How can ROR be shown to decrease over time?
Calculating the average rate at different stages of the reaction
What are the four signs of a chemical reaction?
Colour change
Effervescence
Precipitation
Energy change
What is reaction rate?
It describes how quickly a reaction progresses
What effect does large particles have on reaction rate?
Small surface area
Fewer collisions
Slower reaction
What effect does small particles have on reaction rate?
Large surface area
More collisions
Faster reaction
What effect does low temp have on reaction rate?
Less energy
Fewer collisions
Slower reaction
What effect does high temp have on reaction rate?
More energy
More collisions
Faster reaction
What effect does low concentration have on reaction rate?
Less particles
Fewer collisions
Slower reaction
What effect does high concentration have on reaction rate?
More particles
More collisions
Faster reaction
What does higher rate equal?
Faster reaction
Why is it useful to know the rate of reaction?
Safety (eg. Medicines, preventing explosions)
Economy (how quickly can a product be made and sold)
How can we measure how much gas is being produced?
Inverted measuring cylinder filled with water
Gas syringe
Balance (used to measure mass loss)
When is it not appropriate to use an inverted measuring cylinder?
Gas is water soluble
How is ROR defined?
A change in some measurable quantity (mass, concentration, volume etc) over a period of time
What can average rate be used to describe?
How quickly a reaction happens in a specific interval of time
How can we complete a good experiment?
Repeat measurements
Calculate an average for repeat measurements
Measure accurately
Compare your results with literature data
When is measuring mass loss a suitable method of measuring reaction rate?
For reactions which produce a gas less dense that air
What does the slope of the graph correspond with?
Reaction rate
What does steeper slope mean?
Higher rate
Why does steeper slope mean higher rate?
Indicates the quantity of product formed is increasing more rapidly
What does the height of the graph correspond with?
Quantity (volume or mass) of gas produced.
Taller = more produce
What are excess reagents?
Reactants that are not used up when the reaction is finished
What happens when we add more of an excess reagent?
Will it produce more product
Can changing concentration affect height?
Yes but only if the reactant is not in excess
What is crucial when predicting rate graph shapes?
Take into account which reactants in excess, as adding ore of it will not affect the shape of the graph
