4.3 Rates Flashcards
How does increasing temperature increase rate of reaction?
particles gain more kinetic energy
How does increasing concentration increase rate of reaction?
more particles in the same volume
How does reducing particle size increase the rate of reaction?
increases surface area
more contact between reactants
How does using a catalyst increase the rate of reaction?
reduces activation energy, provides alternative path
How does changing pressure increase rate of reaction?
same particles in smaller volume
What is collision theory?
particles must collide with required energy (activation energy) for the reaction
What is activation energy?
amount of energy particles need to react
What is collision frequency?
how often particles collide with each other
What is percentage success?
what percentage of collisions have enough energy
What factors affect rate of reaction?
pressure
concentration
surface area
catalyst
temperature
What factors affect collision frequency?
concentration
pressure
surface area
What factors affect percentage success?
temperature
catalyst
Name an experiment to measure the effect of surface area on rate
marble chip experiment
Name an experiment to measure the effect of temperature on rate
magnesium and acid experiment
Name an experiment to measure the effect of catalyst on rate
hydrogen peroxide experiment
Why are catalysts not included in the equation?
because they are unchanged in the reaction
Which catalyst is used in the hydrogen peroxide experiment?
manganese oxide
How is the scientist able to retrieve the catalyst?
it is not used up in the reaction
What is a catalyst?
substance that increases rate of reaction but remains chemically unchanged
How do catalysts work?
provide an alternative pathway
percentage of collisions with enough energy is higher
more successful collisions
Name an experiment that can demonstrate the effect of concentration on rate
disappearing cross experiment
What is the disappearing cross experiment?
react sodium thiosulphate
solution with hydrochloric acid
In the disappearing cross experiment, which solid is produced?
sulphur
What is the equation for the disappearing cross experiment?
sodium thiosulphate + hydrochloric acid -> sulphur + water + sulphur dioxide
In the disappearing cross experiment, what is the independent variable?
concentration of sodium thiosulphate
In the disappearing cross experiment, what is the dependent variable?
time taken for cross to disappear
In the disappearing cross experiment, what are the control variables?
volume of solution
concentration of HCl
temperature
What does the disappearing cross experiment prove?
rate is proportional to concentration
What is the magnesium and acid experiment?
reacting magnesium with hydrochloric acid
Why does the cross disappear in the disappearing cross experiment?
sulphur is produced
in suspension - makes solution cloudy so cross is not visible under breaker anymore
In the magnesium and acid experiment, what is the independent variable?
temperature of HCl
In the magnesium and acid experiment, what is the dependent variable?
time take for Mg to disappear
In the magnesium and acid experiment, what are the control variables?
mass and surface area of Mg
volume and concentration of HCl
What is the equation for the magnesium and acid experiment?
magnesium + hydrochloric acid -> magnesium chloride + hydrogen
What does the magnesium and acid experiment prove?
temperature is not proportional to rate
What is the equation for rate of a reaction?
rate = collision frequency x percentage success
What is the hydrogen peroxide experiment?
hydrogen peroxide broken down into water and oxygen
What is the equation for the hydrogen peroxide experiment?
hydrogen peroxide -> water + oxygen
catalysed by manganese oxide
In the hydrogen peroxide experiment what is the independent variable?
catalyst being used
In the hydrogen peroxide experiment what is the dependent variable?
volume of oxygen produced
What are the control variables in the hydrogen peroxide experiment?
volume and concentration of hydrogen peroxide
temperature
mass and surface area of catalyst
What does the hydrogen peroxide experiment prove about rate?
catalyst increases rate
