Chemistry C6 Flashcards
How do you find the rate of reaction from a particular point on a graph?
Use a tangent,
- follow from the point you want to measure
- draw a dot on the line
- use ruler to draw tangent
- draw a triangle to the tangent(bigger=better)
- then use equation for the gradient
What’s the equation for the gradient of a graph?
Gradient= change in y over change in x
or
Gradient= up over across
How can you follow a reaction?
- loss of mass
- production of gas
- colour change
How do you measure the gas coming off of an experiment?
- measuring syringe
- inverted measuring cylinder
Problems with using a inverted measuring cylinder?
- gas is already present
- gas is lost before the bung is placed
Which have faster reaction times?
1) a)low temp
b) high temp
2) a)lump
b) powder
3) a) low concentration
b) high concentration
1) B
2) B
3) B
Collision theory- temperature
Whats’s the difference between Low temp and High temp?
Low temp
-slow movement, not much energy
-when they collide some react and some don’t
High temp
-high speed, lots of energy
-when they collide there are lots of reactions
Collision theory- temperature
Conclusion…
The higher the temperature the higher the rate of reaction will be. This is because the particles have more energy, so they can move around faster. Leading to more successful collisions.
Collision theory- surface area
Lump vs Powder
In the lump there is less surface area so less space to react.
In the powder they are more spread out so there is more available space to react.
Collision theory- surface area
Conclusion…
The larger the surface area, the faster the rate of reaction, this is because there are more particles available to react, leading to more successful collisions.
Collision theory- pressure/concentration
Low vs high concentration
High concentration menas particles are more likely to bump into each other.
Collision theory- pressure/concentration
Conclusion…
The higher the pressure/concentration, the aster the rate of reaction will be, this is because there are more particles in a fixed volume so there is a higher chance of a successful collision.
Collision theory- catalyst
none vs catalyst
Faster with catalyst as particles attach to the catalyst so that the other particles can react with them easier
Le chatelier’s principle
if you change the conditions of a reversible reaction at equilibrium the system will try counteract the change
Equilibrium
A state in which opposing forces are balanced
What is the formula for rate of reaction?
Rate of reaction= amount of reactant used or amount of product formed ÷ time
What is the formula for a mean rate of reaction in terms of reactants?
quantity of reactant used/time taken
What is the formula for a mean rate of reaction in terms of products?
quantity of reactant product formed/time taken
What is “collision theory”?
The theory that chemical reactions only occur when particles collide with enough energy
What factors can affect the rate of a reaction?
Temperature, surface area of a solid, concentration or reactants in solution, pressure of gases
State the effect of increasing the surface area on the rate of a reaction
Increases the rate
How can you increase the surface area of a solid?
Break it into smaller pieces.
Explain why increasing the surface area increases the rate of a reaction
More particles are available to collide, there are therefore more frequent collisions between reactants.
State the effect of increasing the concentration on the rate of reaction
Increases
Explain why increasing the concentration increases the rate of reaction
More particles in the same volume, therefore more frequent collisions between reactants.
State the effect on increasing the pressure of a gas on the rate of reaction
Increases
Explain why increasing the pressure of a gas increases the rate of a reaction
More particles in the same volume, therefore more frequent collisions between reactants.
State the effect of increasing the temperature on the rate of reaction
Increases
What is the activation energy?
The energy needed to break bonds to start a reaction
Explain why increasing the temperature increases the rate of reaction
Increases the kinetic energy of the particles so more frequent collisions, it also increases the number of particles which have the activation energy therefore more collisions result in a reaction.
What is a catalyst?
Something which changes the rate of a reaction but is not used up in that reaction
How do catalysts speed up reactions?
They provide another route for the reaction with a lower activation energy.
What is a reversible reaction?
A reaction which can go from reactants to products but also from products to reactants
What chemical symbol represents a reversible reaction?
⇌
If a reaction is exothermic in the forward direction what will it be in the reverse direction?
Endothermic
Two reactants require 30kJ to turn into products. What energy transfer is involved when the products turn into reactants?
30kJ is released
What is equilibrium?
When the forward and backwards reactions are occurring at the same rate in a closed system
How is the amount of reactant changing at equilibrium?
It is not changing
How is the amount of product changing at equilibrium?
It is not changing
