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
Avogadro’s Law - gases
Equal volumes of all gases, when measured at the same temperature and pressure, contain an equal number of particles.
Formula containing amount of gas (n), volume of gas (Vstp) and Molar Volume
amount of gas = (volume of gas stp)/(molar volume)
n=V/22.7
Standar Conditions for gases
T=273K
P=100kPa
Vm= 22.7 dm^-3
Kinetic Molecular Theory
- particles are in constant motion
- that motion depends upon the absolute temperature measured in Kelvin
Absolute Zero
means that there is no particle motion
Temperature definition
is a measure of the kinetic energy or motion of particles
Pressure definition
the force the particles’ collisions on the walls of the container
Boyle’s Law
Pressure and volume are inversely proportional , as the volume increases the pressure decreases
PV = constant
Pressure Law
temperature and pressure are directly proportional if the volume is kept constant
P/T = constant
Charles’s Law
volume and temperature are directly proportional if pressure is constant
V/T = constant
Formula for when one of the conditions is changed to a fixed amount of gas
P1V1/T1 = P2V2/T2
Ideal Gas
the particles have negligible volume
there are no attractive forces between the particles
the kinetic energy of the particles is directly proportional to the absolute temperature
- this model tends to break down at low temps and high pressures
Formula containing n, c, V
concentration = moles/volume
c=n/V
Formula for the diluting of a solution
c1V1=c2V2
as the number of moles of solute remains constant
