Chapter 10 - Reaction rates and equilibrium Flashcards
What is reaction rate ?
The change in concentration of a reactant or product in a given time
What makes an effective collision?
- Particles must have sufficient energy
- Particles must collide in correct orientation
Which factors can change the rate of a chemical reaction?
- Concentration and pressure
- Temperature
- Use of a catalyst
- Surface area
What effect does increasing temperature have on reaction rate?
Reaction rate increases
Explain why increasing temperature has its effect on reaction rate
- Particles have more kinetic energy
- They move at higher speeds
- Collide more frequently
- More successful collisions
- Rate increases
What is the rule of thumb for reaction rate and temperature?
A 10C increase in temperature doubles the rate.
What effect does increasing concentration/pressure have on reaction rate?
Reaction rate increases
Explain why increasing concentration/pressure has its effect on reaction rate
- Concentration increases
- More particles in the same volume
- More frequent collisions
- More successful collisions
- Rate increases
How can progress of a chemical reaction be followed ?
- Monitoring the removal of a reactant
- Following the formation of a product
What are the two methods of determining reaction rate, when a gas is produced?
- Monitoring the volume of gas produced
- Monitoring the loss of mass of reactants
What are the main features of Boltzmann distribution ?
- No molecules have zero energy
- Area under the curve is equal to the number of molecules
- No maximum energy
How does a Boltzmann distribution curve change when temperature is increased?
- The peak is lower and shifted to the right
- A greater proportion of molecules can overcome the activation energy
How does a Boltzmann distribution show the effect of a catalyst?
- Activation energy with a catalyst is lower than the normal activation energy
- Therefore a greater proportion of molecules exceed the new lower activation energy
What is a dynamic equilibrium?
The equilibrium that exists in a closed system when the rate of the forward reaction is equal to the rate of the reverse reaction and concentrations do not change.
What is Le chateliers principle ?
When a system in dynamic equilibrium is subjected to an external change, the system readjusts itself to minimise the effect of that change.
What is said to happen if equilibrium shifts to the right ?
More products are formed
What is said to happen if equilibrium shifts to the left ?
More reactants are formed
Where does the equilibrium shift if the concentration of the reactants increases ?
Equilibrium shifts to the right
Where does the equilibrium shift if the concentration of the products decreases ?
Equilibrium shifts to the right
Where does the equilibrium shift if the concentration of the reactants decreases ?
Equilibrium shifts to the left
Where does the equilibrium shift if the concentration of the products increases ?
Equilibrium shifts to the left
Which reaction investigates the change of position of equilibrium with concentration ?
Chromate ions to dichromate ions
What is the colour change from chromate ions to dichromate ions ?
Yellow to orange
When the forward reaction is exothermic, what does an increase in temperature do ?
- Position of equilibrium shifts to the left
- More reactants are made
When the forward reaction is exothermic, what does a decrease in temperature do ?
- Position of equilibrium shifts to the right
- More products are made
When the forward reaction is endothermic, what does an increase in temperature do ?
- Position of equilibrium moves to the right
- More products are made
When the forward reaction is endothermic, what does a decrease in temperature do ?
- Position of equilibrium moves to the left
- More reactants are made
Which reaction investigates the change of position of equilibrium with concentration ?
Cobalt chloride dissolving in water
What is the colour change in the cobalt chloride in water reaction ?
Pink to blue
Where does the equilibrium shift if the pressure in the system is increased ?
The equilibrium shifts to the side that has fewer gaseous moles, reducing the pressure of the system
Where does the equilibrium shift if the pressure in the system is decreased ?
The equilibrium shifts to the side that has more gaseous moles, increasing the pressure of the system
Which reaction investigates the change of position of equilibrium with concentration ?
Nitrogen oxide to nitrogen tetroxide
What is the colour change from nitrogen oxide to nitrogen tetroxide ?
Brown to colourless
What is the effect of a catalyst on equilibrium?
- Does not change the position
- Speeds up the rates of forward and reverse reactions equally
What is different about the equilibrium constant to regular constants ?
- Only constant at a given temperature
- Units change depending on the reaction
