C8 - Rates & Equilibrium Flashcards
How is rate of reaction calculated?
Rate of reaction = amount (e.g. grams, cm3) of reactant used or product formed / time
Rate of reaction (mol/s) = Moles of reactant used or product formed / time
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
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. increases = faster reaction
More reactants = more frequent collisions
Describe and explain the effect of increasing
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, e.g. block of magnesium reacts slower with acid then magnesium powder.
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 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 and the concentrations of reactants and products remain constant.
Describe measuring the rate by monitoring the
volume of a gas.
Connect a gas syringe to a reaction flask and measure the volume of gas formed in time intervals. Plot a graph of volume vs time.
