Stoichiometry Flashcards
Definition of a substance
matter with constant composition. All particles have the same properties.
Definition of a mixture
Matter with variable composition. Made from two or more substances that are not chemically bonded and so retain their original properties.
Definition of a homogenous mixture
a mixture made up of particles that are uniformly distributed
Definition of a heterogenous mixture
a mixture made up of particles that are not uniformly distributed
Common Polyatomic ions
Ammonium - NH4+
Carbonate - CO3 2-
Hydrogen Carbonate - HCO3-
Hydroxide - OH-
Nitrate - NO3-
Nitrite - NO2-
Phosphate - PO4 3-
Phosphite - PO3 3-
Sulfate - SO4 2-
Sulfite - SO3 2-
Oxalic Acid - (COOH)2 2-
Peroxide - O2 2-
Naming anions
-ate = max number of O
-ite = less O
Common Acids
Phosphoric acid - H3PO4
Ethanoic acid - CH3COOH
Properties of solids
particles closely packed
inter-particle forces are strong
particles vibrate in position
fixed shape
fixed volume
Properties of liquids
particles more spaced
inter-particle forces weaker
particles can slide over each other
no fixed shape
fixed volume
Properties of gas
particles spread out
inter-particle forces negligible
particles move freely
no fixed shape
no fixed volume
What is the kinetic theory?
average kinetic energy of the particles is directly related to the temperature of the system
When does a substance melt?
a substance melts at the temperature at which the disruptive effect of the vibrations just overcomes the ordering effect of the forces of attraction
When does boiling occur?
at a specific temperature, determined by when the vapour pressure reaches the external pressure
What is the mole?
it is a fixed number of particles and refers to the amount, n, of substance
Avogadro’s constant
defines the mole as the unit of amount in chemistry
6.02 x 10^23
Formula containing n, N and NA
moles = (no. of particles) / (Avogadro’s constant)
n=N/NA
Relative Atomic Mass definition
Ar of an element is the weighted average of the masses of its isotopes relative to 1/12 of the mass of a C12 atom.
Ar = (weighted average of one atom of the element)/(1/12 mass of one atom of C12)
*values do not have units
Relative Molecular Mass definition
Mr of a substance is the weighted average of the masses of the molecules relative to 1/12 of the mass of a C12 atom.
What is the Molar Mass?
the mass of one mole of a substance
Formula containing n, m and M
moles = mass/molar mass
n=m/M
what is the Molecular formula
it gives the total number of atoms of each type in a molecule
* to calculate need the molar mass
What is the Empirical Formula?
is a formula which gives the lowest whole number ratio of atoms in a molecule
*assume 100g sample for calculations
Limiting Reagent
is the reactant that determines the quantity of product
% yield calculation
% yield = ((mass of experimental yield)/(mass of theoretical yield)) x 100
