Block 3 Exam Questions Flashcards
What is the rate of a chemical reaction?
The change in concentration per unit time (mol L-1)
What is the instantaneous rate?
The rate at a particular time during the course of the reaction (and is the same as the slope of conc vs time)
What is the average rate?
- 1/a (delta A/ delta time)
What is the initial rate?
The instantaneous rate at the start of the reaction
Factors that affect rate of reaction?
- The nature of the reaction (eg metallic sodium with oxygen vs iron)
- Concentration of reactants
- Temperature
- Physical state of reactants
- Presence of catalysts
- Action of light
What is a rate law?
The relationship between the rate of a chemical reaction and the concentration of reactant(s)
What is a first order reaction?
The rate is proportional to the concentration of the reactant
Rate equal [A]
What is a second order reaction?
Where the rate is proportional to the square if the concentration
Rate equivalent to A^2
What are zero order reactions?
Where the rate is independent of concentration
What is a third order reaction ?
Where the rate is proportional to the cube of concentration
What is the rate constant?
The proportionality constant between rate and concentration (given by the symbol k)
Rate law for a first order reaction?
R= Ro e^(-kxt)
Which plots give a straight and curved line?
1st order = straight
2nd order = curved
Integrated rate law for a second order reaction?
1/R = 1/Ro + kt
What’s the half life and equation?
The time (in seconds) for the concentration of the reactant to fall to half its initial value (denoted by t1/2)
