How Far and How Fast Flashcards
Define rate of reaction.
Change in concentration of a reactant or a product per unit time.
If the order is 0 with respect to a reactant, what does that mean?
Changing concentration of the reactant has no effect on the rate.
What is the effect on rate in a first order reaction?
Rate is directly proportional to the concentration.
What is the effect on rate in a second order reaction?
Change in rate = change in concentration squared
How is the overall order of a reaction calculated?
Sum of individual orders
How could you measure the rate of reaction experimentally (different methods)?
Use a colorimeter at suitable intervals if there is a colour change.
If gas is evolved, use a gas syringe to collect volume of gas evolved, or measure the change in mass of the reaction mixture.
What does half life mean?
The time taken for the concentration of a reactant to decrease by half.
What is the relationship between first order reactions and half life?
First order reactants have constant half lifes.
How would you draw a rate concentration graph?
Plot [A] against time, draw tangents at different values —> draw a secondary graph of rate against [A]
What is the relationship between rate and time?
Rate is proportional to 1/t
How do you determine the rate constant from a rate concentration graph of first order?
k = rate/concentration
What is the rate determining step?
The slowest step in a reaction with multiple steps.
How does the rate determining step link to the species involved in the rate equation?
Any species involved in the rate determining step appear in the rate equation. Species only involved after the rate determining step do not appear in the rate equation.
For a reactant in the rate equation, what indicates how many molecules of that reactant are involved in the rate determining step?
The order of the reactant
What affects the value of the rate constant for a given reaction?
Temperature, nothing else
What does it mean when a reaction is at equilibrium?
The rate of forward and reverse reactions are equal.
What are the methods that can be used to measure equilibrium?
- measure change in colour or colour intensity using colorimeter
- use pH probe
- measure electrical conductivity
- titration — used when equilibrium is slow so that titration can be completed before there is much change in equilibrium mixture
What does mole fraction mean?
The amount of a given component in a given reaction mixture.
Write the equation used to calculate mole fraction.
mole fraction = no. moles of substance A/ total no. moles of all substances
What does partial pressure mean?
The pressure exerted by a single species in a reaction vessel.
Write the equation used to calculate partial pressure.
Partial pressure = mole fraction x total pressure
What is the relationship between concentration of a substance and its partial pressure?
Concentration of a substance is proportional to its partial pressure
What does it mean when k is greater than 1?
Reaction favours the product
What does it mean when k is lesser than 1?
The reaction favours reactants
What is the effect of increasing temperature on k?
Equilibrium shifts to the direction of the endothermic reaction.
What is the effect of decreasing temperature on k?
Equilibrium shifts to the direction of the exothermic reaction
What effect does a catalyst have on k?
catalysts does not affect the position of equilibrium, they only have an effect on the rate of reaction.
