Rates of Reaction Flashcards
What is a rate of reaction?
a measure of how quickly a reactant is used up
What is needed for a chemical reaction?
- reactants must collide
- must have enough energy to react
What is activation energy?
the minimum amount of energy that particles need for a reaction
what is a catalyst?
a substance that changes the rate of a chemical reaction
How do catalysts work?
providing alternative reaction pathways
What is an endothermic reaction?
takes in the energy from the surroundings so temperature decreases
What are 3 examples of exothermic reactions
Combustion
Neutralisation
Oxidation
What are two endothermic reactions?
Citric acid + sodium hydrogen carbonate
Thermal decomposition
what is a reaction profile diagram?
a diagram that shows the energy change in a chemical reaction
What is the formula for calculating the rate of a reaction
mass of product made or lost / time taken
What are ways of measuring the rate of reaction
change in mass
precipitation or colour change
volume of gas gained or lost
What is an exothermic reaction?
transfers energy to the reaction increasing the temperature
How can you measure precipitation?
measure the time it takes for a mark to disappear
How do you measure colour change?
the time it takes for the colour to change
What are issues with measuring the rate of reaction by observing colour change and precipitation?
It is subjective
you can’t use your results to plot a graph
How can you calculate the Rate of Reacting by measuring change in mass?
Use a balance
Take measurements regularly
Plot your results on a graph
Draw and tangent and calculate its gradient to find rate
What is the most accurate way to measure rate of reaction?
Change in mass
How can you use a gas syringe to measure the rate of a chemical reaction?
Use a gas syringe to monitor how the volume of gas changes over time
What are factors that affect the rate of a chemical reaction?
Temperature
Concentration of solution or gas
Surface area
presence of a catalyst
Why how does increasing the temperature increase rate of reaction?
Particles move faster
They will collide frequently
will have more kinetic energy
How does creating the concentration or pressure increase rate of reaction?
the number of particles per unit will increase
increase collisions
How does increasing the surface area of a solid affects rate of reaction?
more frequent collisions in a greater number of reactions
What is collision theory?
for particles to react they have to collide with sufficient energy in the right direction
How does a catalyst increase rate of reaction?
speed up reactions by lowering activation energy
by giving them a different reaction oathway
What is activation energy?
the minimum amount of energy that particles require to react together.
Why do particles need activation energy?
They need energy to break bonds of reactants so reaction can start
On a time graph of a chemical reaction what does a steep gradient of the line tell us?
reaction was fast
Why do concentration/time graphs plateau?
the reactants are used up
What is the formula to find the gradient of a line?
Gradient = change in y / change in x
What can be used for empirical formula?
Mass
Ram
Divide
Dsmall
F
