1. stoichemetric relationships! Flashcards
what is a homogenous mixture
uniform composition AND properties
heterogenous do NOT
given differing boiling points in a mixture, how would they be seperated?
fractional distillation
eg air
how to determine ionic equation
- write full chem eqn
- break down compounds into ions
- cancel repeated ions on each side
boiling vs evaporation?
boiling at specific temp – vapour pressure reaches external atmospheric pressure
evaporation only at surface + at temps BELOW boiling point
when given a graph of state change hwo to explain the flat parts (no change in temp)
no increase in kinetic energy or temp bc ALL THE ENERGY GOES INTO BREAKING BONDS
define the avogadro constant!
the number of particles equivalent to the RELATIVE ATOMIC MASS / MOLECULAR MASS of a substance in grams
what is the value of the avogardo constant
6.02 x 10^23 g/mol
what is avogadros constant used for
number of atoms / particles
define molar mass
one mole of a substance = same number of atoms in 12g of 12C
define relative atomic mass
weighted average mass of one atom compared to one twelfth of the mass of a carbon-12 atom
define relative isotopic mass
mass of a particular atom of an isotope compared to 1/12th the mass of a 12C atom
define isotopes
atoms of the same element with different number of neutrons
define relative atomic mass
weighted average mass of a molecule compared to 1/12th the mass of a 12C atom
define empirical formula
the simplest whole number ratio of the atoms of each element present in one molecule/formula unit of the compound
define percentage yield
how much of a particular product you get from reactants compared to max theoretical amt
actual vs theoretical yield
actual: mol/mass obtained experimentally
theoretical: mol/mass obtained thru mass creation
what is avogardos law used for
determining mole ratio of reacting gases to be determined from volumes of the gases
what is avogardos law
equal volumes of gases must contain the same number of molecules
(At standard temp and pressure. 1 mol)
value for avogardos law
standard temp + pressure
1 mole of gas = vol of 22.7dm3
conditions of STP (standard temp and pressure)
0C / 273K
100kPa
define the kinetic theory of gases
states that molecules in gases are constantly moving
5 assumptions of the kinetic theory of gases
- gas molecules move very fast and randomly
- molecules hardly have any volume
- no intermolecular forces = gas molecules do not attract or repel each other
- elastic collisions: no kinetic energy lost when gas molecules collide
- temperature of gas directly proportional to average kinetic energy of molecules
volume of a gas depends on 2
temperature
pressure
ideal gas equation
PV = nRT
pressure x volume = moles x gas constant (8.31) x temp
what is the gas constant?
8.31 J/K/mol
what unit is volume in in the ideal gas equation
m3
(1 m3 = 1000dm3)
what unit is pressure in the ideal gas equation
Pa
1 kPa = 1000 Pa
what unit is temperature in the ideal gas equation
K
C + 273 = K
conversion from m3 to cm3
multiply by 10^6
vice versa
what is Boyle’s law
(in gases) pressure is invesely proportional to the volume (at a constant temperature)
PV is a constant
pressure against volume graph gives? vs pressure against 1/vol
curved inwards, down (like and L)
gives a straight directly increasing line
at what conditions do real gases deviate from ideal gas equation 2 + why?
high pressures
low temperatures
assumes tiny volume of molecules vs container BUT at these conditions = closer tgt = takes up larger vol of space
pressure less than expected bc itnernolecular forces exist when molc close tgt
what is a standard solution
concentrations known precisely
(use volumetric flask!)
what is the concentration of a solution?
amount of solute dissolved in a solvent to make 1dm3 of solution
cm3 to dm3
divide by 1000
define ppm
parts per million
mass of 1 mg dissolved in 1 dm3 of water (or 1kg of water)
1 dm3 = how many litres ?
1 litre / kg
parts (in ppm) to kg
parts is in mg
x 10^-6 (aka 1 mil)
charge of CO3 ion?
2-
uncertainty of burette
+- 0.05
