Topic 3 - Quantative Chemistry Flashcards
What does the relative atomic mass show
The mass of the element
How do you find the relative formula mass ( mr) of a compound
Add together the relative atomic masses of all the atoms in its formula
The total mass of the products in a reaction is equal to…
… the total mass of the reactants
Atoms cannot be _______ or _________
Created or destroyed
How can the princible of conservation of mass help you solve a chemical reaction
If you know 2 of the reactant + reactant = product, you can work out the other part because the reactants and product should be the same mass
What’s the difference between reactions in a closed and non enclosed system?
No substances can enter or leave a closed system but can in an non enclosed system
What is a solution
Mixture of a solvent and a solute
What is a solute
The dissolved substance in a solution
What is a solvent
The liquid in which the solute dissolves to form a solution
Concentration g/dm cubed =
Mass of solute in g ÷ volume in dm cubed
How can concentration be increased (2)
1.Dissolving more solute into solution
2.allowing some of the solvent to evaporate
Percentage atom economy =
Total Mr of desired product ÷ total Mr of all reactants ×100
What is the theoretical yield?
The maximum possible mass of a product that can be made in a chemical reaction
Reasons why the mass of a product might be less than the maximum theoretical mass (3)
- The reaction is reversible
- Some if the product may be lost during the process
- Some of the reactants may react in ways different to the expected reaction
Percentage yield =
Mass of product actually made ÷ maximum theoretical mass of product × 100
What are the 4 key features of a chemical reaction
- compounds are broken up or formed
- adleast 1 new substance is created
- Measurable energy change
- No atoms are created or destroyed
Percentage mass of an element in a compound=
(Reletive atomic mass × number of atoms of that element ÷ Mr of the compound) × 100
What is Avogadro constant?
6.02 × 10 ²³
What is the mole and how many particles are in one mole?
The mole is the name given to the amount of a substance.
In one mole there’s 6.02 ×10 ²³ particles
The number of moles in a mass =
Mass in g ÷ reletive formula mass
How do you show that mass is conserved in a reaction?
Add up the reletive formula masses on each side and they should be the same number
How can you balance equations using reacting masses? (4)
1)divide mass of each substance by its Mr to find number of moles
2)divide number of moles by smallest number of moles in reaction
3)if any numbers aren’t whole multiply all by the same number
4)write the balanced symbol equations by putting the numbers in front
How to calculate theoretical yield (5)
1)write out balanced equation
2)calculate Mr
3)calculate number of moles
4) look at the ratio of moles in equation
5)calculate mass
Volume of gass =
Mass of gas ÷ Mr of gas ×24
