Chemistry Topic 6 - The Rate And Extent Of Chemical Change Flashcards
What are the various units for rate of reaction?
Can include g/s or cm^3/s or mol/s
Name three common ways of measuring rate of reaction
-loss in mass of reactants
-volume of gas produced
-time for a solution to become opaque
Describe measuring the rate by monitoring mass loss
Place the reaction flask on a balance. In these reactions a gas is given off, so record the decrease in mass in time intervals
Describe measuring the rate by monitoring the volume of a gas
Connect a gas syringe to a reaction flask and measure the volume of a gas formed in time intervals. Plot a graph of volume vs. Time
Describe measuring the rate by monitoring the disappearance of a cross
Take a piece of paper and mark a cross on it. Put the reaction flask on this cross. Mix the reagents, and measure how long it takes for a cloudy mixture to conceal a cross
State five factors affecting the rate of a chemical reaction
-concentration of reactants
-pressure of gases (volume)
-surface area
-temperature
-catalysts
What is the collision theory?
Chemical reactions can occur only when reacting particles collide with each other with sufficient energy (more than or equal to activation energy)
Describe and explain the effect of increasing concentration on the rate of reaction
Conc. increase = faster reaction
More reactants = more frequent collisions
Describe and explain the effect of increasing the surface area
If solid reactants are in smaller pieces, they have a greater surface area
Increasing the surface area of solid reactants increases the frequency of collisions. And so increases the rate of reaction
What is a catalyst and how does it work?
A catalyst changes the rate of reaction but is not used up. It increases rate of reaction by providing a different pathway for the reaction that has a lower activation energy.
What is an enzyme?
An enzyme is a molecule that acts as a catalyst in a biological system
What is a reversible reaction?
A reversible reaction occurs when the products of a reaction can react backwards to produce the original reactants
When is dynamic equilibrium reached?
In a closed system, when the forward and reverse reactions occur at the same rate an fate concentrations of reactants and products remain constant
Describe Le Chatelier’s principle
If a system is at equilibrium and a change is made to any of the conditions, then the system responds to counteract change and restores the equilibrium
Describe the effect of a catalyst on the position of the equilibrium
No effect
It just speeds up both forward and backward reactions equally
I.e. equilibrium is achieved faster
