The Rate & Extent of Chemical Change Flashcards
What are the two equations to calculate the rate of reaction?
Rate = Quantity of Reactants Used ÷ Time
Rate = Quantity of Products Formed ÷ Time
What units are used to measure rate of reaction?
Quantity: grams (g), cm³, moles (mol)
Time: seconds (s), minutes (min)
Give examples of reactions with slow, medium, and fast rates
- Slow: Rusting of iron (years/decades)
- Medium: Reaction of magnesium with acid (gentle bubbling)
- Fast: Explosions like fireworks (fractions of a second)
What is the difference between the average and instantaneous rate of reaction?
- Average rate: Calculated over the whole reaction time.
- Instantaneous rate: Calculated at a specific point in time.
How do graphs for reactants and products look during a reaction?
- Reactants: Starts high and slopes down as reactants are used up
- Products: Starts at zero and slopes up as products are formed
What does collision theory state about reactions?
- Particles must collide with sufficient energy (activation energy) to react
- If they collide with less energy, no reaction occurs—they bounce apart
What are the four main factors that affect the rate of reaction?
- Temperature
- Concentration/Pressure
- Surface Area
- Presence of a Catalyst
How does increasing temperature affect the rate of reaction?
- Particles gain more energy and move faster.
- Collisions are more frequent and energetic.
- More collisions exceed the activation energy, increasing the reaction rate.
How does increasing concentration or pressure affect the rate of reaction?
- More particles per unit volume
- Increases collision frequency
- Increases the rate of reaction
Why does powdered magnesium react faster than a solid block of magnesium?
- Powder has a higher surface area to volume ratio
- More collisions can occur
- Higher frequency of collisions increases the reaction rate.
What is a catalyst?
A substance that increases the rate of a reaction without being chemically changed, or used up
How do Catalyst affect a reaction?
- Lowers activation energy by providing an alternative pathway
- Increases the proportion of successful collisions
Give examples of catalysts?
- Transition metals (e.g., cobalt, nickel)
- Enzymes in biological reactions
What is activation energy?
The minimum energy particles need to collide and react successfully
How does a catalyst change a reaction profile?
It lowers the activation energy, making it easier for particles to react
