C3 Quantitative Chemistry Flashcards
(38 cards)
What is activation energy?
The minimum amount of energy required for a reaction to happen
What is a catalyst?
A chemical which speeds up the rate of a chemical reaction without being used up. They lower the amount of activation energy needed. They provide an alternate energetic pathway.
What is equilibrium?
The balance of the forward and backward reaction
What is equilibrium to the left?
The backward direction is favoured. The backward direction has a faster rate.
What is equilibrium in the middle?
Forward and backward reactions are happening at the same rate.
What is equilibrium to the right?
The forward reaction is favoured. The forward reaction has a faster rate.
What is the Haber process?
200 atmospheres pressure
200 - 250 degrees
Uses iron as a catalyst
What is Le Chatelier’s principle?
Different conditions will affect the equilibrium point.
Temperature - higher temperature favours endothermic reaction
Concentration- higher reactant concentration favours forward direction
Pressure - higher pressure favours side that makes fewer molecules
What is RAM?
The mass of one atom of an element
What is RFM?
Relative formula mass - mass of a molecule
How do you work out percentage composition by mass?
We can work out what percentage of a compound is a certain element using % mass = RFM of an element/ RFM of the molecule x100
When would it appear that a reaction loses mass?
When a gas is produced
When would it appear that a reaction gains mass?
When oxygen in the air is involved
What is percentage yield?
Mass produced x 100/ expected mass
How much do you make compared to how much you predicted
How can yield be reduced?
Product escapes
Product is left behind
Practical losses from pouring etc
Reaction is incomplete
What is a mole?
6.02 x 10^23 particles
What is Avogadro’s constant?
1 mole = 6.02 x 10^23 particles
What is the reacting masses calculation?
Mass = Mr x moles
What do you write down the side of a reacting masses calculation?
Mass
Mr
Moles
Ratio
What are molar ratios?
Balancing equations tells you how many moles there are of a substance. Balancing number = number of moles.
How can we use moles to balance equations?
Equation
Mass
Mr
Mole
Ratio
Simplify - divide by smallest number of
What is excess?
When any chemical reaction occurs, we will tend to have more of one of the reactants than we need.
What is limiting?
One reactant will be completely used up.
What do we write down the side of a limiting reactants question?
Mass
Mr
Moles
Ratio
I have
I need
I have
So
