Rate Of Reactions Flashcards
What is the rate of reaction?
Speed at which reactants are turned into products
How does the slope/gradient on a graph indicate rate of reaction?
Steeper the line, faster the rate of reaction
Why are rate of reactions usually fastest at the beginning of experiment?
The concentration of reactants is the highest
What is activation energy?
The minimum amount of energy needed for a reaction to take place
What does this energy do during successful collisions?
The energy helps to breaks bonds so atoms can be arranged to make new substances
What is the collision theory?
Reactions occur when particles of the reactants collide
More collisions occur when the particles are closer together or moving faster
Only those with enough activation energy required can react and be more successful or efficient
How does concentration affect rate of reaction?
Increasing the concentration of solutions, increases the rate of reaction
This is because there are more particles reacting in the same volume so collisions occurs more often
How does surface area affect reaction rates?
Increasing the surface area to volume ratio (decreasing the size of solid pieces but keeping total volume same) increases rate of reaction
Therefore there is more surface for collisions to occur on, so collisions occur more often
How does pressure affect reaction rate?
Increasing the pressure increase the rate of reaction
So, the particles are squashed into a smaller space/closer together so collisions occurs more often
How does temperature affect the rate of reaction?
Increasing the temperature increases the rate of reaction
The reactant particles speed up and have more energy. They therefore collide more often and causes more particles to have enough energy to react when collide - more effective collisions
What is the Core Practical with Marble chips to determine how surface area affect reaction rates?
1) Set up a conical flask with a delivery tube connected to a inverted measuring cylinder in water
2) Measure 40cm cubed of dilute hydrochloric acid into the comical flask
3) Add 5g Of small marble chips to the flask
4) Stopper the flask and start the stop clock
5) Note down the total volume of gas produced after every 30 seconds until reaction is finished
6) Repeat using marble chips which increase by 5g each time
What is the Core Practical for seeing how temperature affects reaction rates?
1) Place 50cm cubed of sodium thiosulfate solution into a 300cm cubed conical flask
2) Measure out 5cm cubed of dilute hydrochloric acid in a test tube
3) Clamp the conical flask in a water bath at a certain temperature and Place the test tube in a rack in the same water bath and record the temperature.
4) After 5mins, remove the flask and place it on a piece of white paper marked with a cross
5) Add the acid to the thiosulfate and start the stop clock
6) Stop the clock when the solution isn’t colourless and you cant see the cross
7) Note this time and take the final temperature
8) Repeat with 3 or 4 other temperatures between 20 - 50 degrees.
What is a catalyst?
A substance that increase the rate of reaction without being changed or used up in the reaction
How do catalysts work?
Decrease the activation energy
How are enzymes biological catalysts?
Catalyse reactions in cells for respiration, photosynthesis e.t.c
Substrate fits the active site but at a low temp or high temp it denature it
Enzymes can only catalyse one specific reaction or fit in one specific substrate
