Calculations with mass Flashcards
What is the conservation of mass
Atoms cannot be created or destroyed in a chemical reaction
Why in some reactions does mass decrease
Gas is produced in the reaction and lost to the surroundings
Why in some reaction does mass increase
A reactant is a gas
How to work out Mr (formula mass)
Relative atomic masses of all atoms in formula
What is the avogadro constant
One mole of a substance contains 6.02 x 10 to power of 23 of atoms, ions
Use for liquids and gases usually
How to calculate mass of unknown when given mass (4)
Balance symbol equation
Calculate moles (do not use big number when calculating Mr) using moles = mass/Mr
Put into ratio to work out moles of unknown substance (use big numbers in front of symbol)
Calculate mass of unknown using mass = moles x Mr
What does it mean if a reactant is in excess
It is left over at the end
What is a limiting reactant
The reactant that runs out
How to work out limiting reactant (3)
Balance equation
Work out moles using mass
Take one and use ratio to
Equation to work out concentration if unit is g/cm cubed
Concentration = mass x 1000/volume
Equation to work out concentration is unit is g/dm cubed
Concentration = mass/volume
