Quantitative chemistry Flashcards
What is the small number on top of an element symbol? What is the one under?
On top= mass number
Under= atomic number
What is the law of conservation of mass?
No atoms are lost during chemical reactions so the mass of the products equal the mass of the reactants.
How do you find out the number of neutrons an element has?
Mass number- atomic number
What is Ar?
Ar= relative atomic mass
Define relative atomic mass
The average mass of an atom taking into account the masses of isotopes that make up the element.
Why might some reactions in a non-closed system appeared to have had a change in mass?
A reactant or product is gas and it’s mass has not been taken into account
How do you work out the relative formula mass?
Add together the relative atomic masses of all the atoms in that compound molecular formula
Define relative formula mass
Mass of a molecule or compound
What is the relative formular mass of:
Sulphur
Sodium chloride
Water
sulphur= 32
sodium chloride= 58.5
water= 18
What is the equation to find percentage mass of an element in a compound?
percentage mass of an element in a compound= (Ar x number of atoms of that element/ Mr of the compound) x 100
What is Avogadro’s constant?
6.02 x10^23
In one mole of carbon how many particles are there?
6.02 x 10^23
In one mole of oxygen how many particles are there?
6.02 x 10^23
What is 1 mole of a substance the same as?
It’s Ar (If as atoms) or Mr (if as molecules )
What is the equation for moles?
moles= mass/ Mr or Ar
