Topic 3 - Quantitative Chemistry Flashcards
How do you calculate the percentage by mass of an element in a compound?
(Ar X number of atoms of element/Mr of the compound) X 100
What is the RFM of a compound?
The RAM of all atoms added together in that compound
What is a mole?
The name given to an amount of a substance
What is the Avogadro constant?
6.02 X 10^23
How do you calculate the number of moles?
Mr (of an element or compound)
What does the conservation of mass law mean in a chemical reaction?
No atoms are created or destroyed so the Mr of the reactants must equal the Mr of the products
What is the limiting reactant?
The reactant that will be used up first and stop the reaction from occurring
What does it mean if a reactant is excess?
It will not be used up completely in a reaction
How do you calculate the volume of a gas?
Mass of gas
—————— X 24
Mr of gas
How much room does one mole of a gas take up at 20 degrees?
24 dm^3
How do you calculate the concentration?
Mass of solute or number of moles/Volume of solvent
How do you calculate atom economy?
Relative formula mass of desired product
————————————————————- X 100
Relative formula mass of all reactants
How do you calculate percentage yield?
Mass of product actually made
——————————————————— X 100
Maximum theoretical mass of product
How can you tell if the percentage yield is incorrect?
It is over 100
