Unit 3 - Stoichiometry Flashcards
Molecular formula
The number and type of different atoms in a molecule e.g. CO2
Empirical formula
Simplest whole number ratio for different atoms e.g. H2O2 = OH
Valency
Number of electrons gained or lost
Valency of all groups
- Group I = 1
- Group II = 2
- Group III = 3
- Group IV = 4
- Group V = 3
- Group VI = 2
- Group VII = 1
- group VIII = 0
Ionic compound features
- Ions are charged to get full outer shells
- Compounds final charge must be neutral e.g. k+ + F- = KF
Word equation
Chemical names of all reactants and products
Symbol equation
Names of substances are replaced by element symbols
Polyatomic ions
Ions that have more than one element, e.g. SO4, covalently bonded but unequal protons and electrons
Charges of polyatomic ions
- Hydroxide/OH = 1-
- Carbonate/CO3 = 2-
- Chlorate/ClO4 = 1-
- Nitrate/NO3 = 1-
- Sulfate/SO4 = 2-
Law of conservation of mass
In a reaction the mass of the reactants will equal the mass of the products - mass is conserved
State symbols
- Solid = (s)
- Liquid = (l)
- Gas = (g)
- Aqueous = (aq)
Notation for multiple molecular ions
Brackets around ion with amount e.g. Al(NO3)3
Ammonium
NH4 = 1+
Ammonia
NH3
Relative atomic mass
Every atom’s mass is relative to 1/12th of carbon - 12
Symbol for relative atomic mass
Ar
Relative molecular mass
The mass of all atoms in a compound or molecule - can be used for ionic compounds
Symbol for relative molecular mass
Mr
Avogadro’s constant
1 mole of a substance has 6.02 x 10^23 atoms in it
Relationship with moles and Ar or Mr
1 mole of a substance is weighs its Ar or Mr in grams e.g. 1 mole of H20 = 18g
Mole, mass and Mr equation
- Mass = Moles x Mr
- Moles = Mass ÷ Mr
- Mr = Mass ÷ Moles
Molar gas volume law
Under same temperature and pressure conditions, equal volumes of different gasses contain an equal number of molecules
Molar gas volume constant
1 mole of a gas = 24dm^3 = 24000cm^3 = 0.024m^3
Room temperature and pressure conditions
25˚C and 1 atmospheric pressure
