QUANTATIVE CHEMISTRY Flashcards
What is relative formula mass?
The relative atomic masses of all the atoms in the molecular formula added together
How do you calculate the percentage mass of an element in a compound?
(relative atomic mass x number of atoms of that element / relative formula mass) x 100
What is avogadros constant?
A mole - 6.02 x 10^23
How do relative atomic mass and mass of one mole relate?
The relative atomic mass of an element is equal to the mass in g of one mole of that element
What is the formula for number of moles?
mass / relative formula mass
How is mass conserved in a reaction?
No atoms can be destroyed or created
Why might the mass change in a reaction?
Not a closed system
A gas is produced into the air
When does a reaction stop?
When all of one reactant is used up so any other reactant is in excess
What is the reactant that is used up in a reaction called?
The limiting reactant
What is the relationship between the product formed and the limiting reactant?
They are directly proportional
How do you find out the volume of a gas at room temperature ?
Volume of gas = moles × 24
How can you calculate concentration?
mass of solute / volume of solvent
Moles of solute / volume of solvent
How do you calculate atom economy?
(RFM of desired product / RFM of all reactants) x 100
How do you calculate the percentage yield?
mass of product made / maximum theoretical mass of product
What can cause a percentage yield to not be 100%?
- In reversible reactions some of the product can be turned back into a reactant
- Could be a side reaction with a gas in the air
- You can lose some liquid/solid/gas when separating from reaction mixture
