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Topic 1 - Stoichiometric Relations (Calculations (Gases …
Topic 1 - Stoichiometric Relations
Things to remember
Polyatomic Ions
Ammonium - NH4^+
Carbonate - CO3^2 -
Hydroxide - OH ^ -
Nitrite - NO2 ^ -
Nitrate - NO3 ^ -
Sulphite - SO3^2-
Sulphate - SO4^ 2-
Phosphite - PO3^3-
Phosphate - PO4^3-
Nitrous Acid - HNO2
Nitric acid - HNO3
Sulphurous Acid - H2SO3
Sulphuric Acid - H2SO4
Phosphorous Acid - H3PO3
Phosphoric Acid - H3PO4
Hi Chloe and DJ, welcome to the calculations topic. It sucks a little, but practise makes perfect. Or so I hear. WE GOT THIS. :<3:
Calculations
Conversions Between Units
Mega (m) - 1 000 000
Kilo (k) - 1000
Deci (d) - 1/10
Centi (c) - 1/100
Milli (m) - 1/1000
Micro (mu symbol) - 1/1 000 000
Nano (n) - 1 / 1 000 000 000
N = n x 6.02 x 10 ^23
where N is the number of particles (ions, atoms, electrons, molecules, formula units)
Solids
n = m/M
Gases
Avogadro's Law: at the same temperature and pressure, equal volumes of different gases have the same number of particles
n = v / 22.7 dm^3
Ideal Gases
An ideal gas has particles which are in random motion and collide with each other and the walls of the container.
The forces of attraction between the particles are negligible
No energy is lost due to collisions,
Average kinetic energy of particles is directly proportional to the temperature in Kelvin of the gas
Boyles Law
P1V1 = P2V2
The pressure exerted by a gas at constant temperature is inversely proportional to the volume occupied by the gas.
Charles Law
V1/ T1 = V2/ T2
At constant mass and pressure, the volume of a gas is directly proportional to the temperature
Gay - Lussac's Law
P1/T1 = P2/T2
At constant mass and volume, pressure is directly proportional to temperature
Ideal Gas Law
PV = nRT
P = Pressure in
Pa
(N/m^2) (1 atm = 101.3 kPa / 760 mm of mercury)
V = volume in
m^3
n = number of moles
T = temperature in
K
R = 8.314 J/K/mol Universal Gas Constant
:warning: units in bold are important for this equation. Convert dm^3 to m^3 by dividing by 1000
Exceptions
- At low temperatures, gas particles can stick together. At high pressures, distances between gas particles are fairly small, and attractive forces between them becomes significant. Neighbouring molecules exert an attractive force, which reduces the interaction of molecules with the container walls. The apparent pressure will be less than ideal (PV/RT will consequently be less than ideal).
Liquids
Concentrations and Titrations
n = c x v
Parts per million : 1mg/ L or 1 mg/ kg of substance
Titration : method used to find the concentration of a unknown solution using the known concentration of a standard solution/ titrant.
Equivalence point / end point: titration has stopped, within one drop
Indicator: Chemical that changes colour to indicate equivalence point
Analyte/ titrate - solution being tested/ measured
https://classroom.google.com/u/0/c/MTQzNDk5MzkwNzVa/t/MjY5NTQ4MjQ4NjNa
List of apparatus needed to conduct titrations
Finding the Limiting and Excess Reactants
1) Balance the chemical equation.
2) Find the number of mols of each reactant.
3) Divide the no. of mols by coefficients found in reactants
4) Reagent with the smaller value is the limiting reagent.
Theoretical and Percentage Yield
1) %Yield = Actual Yield / Theoretical Yield x 100
2) % error = (actual yield - theoretical yield)/ theoretical yield x 100
Definitions
Relative atomic mass: the average mass of all the atoms of an element, taking into consideration the relative abundance of each isotope as compared to 1/12 of C-12 isotope.
Empirical formula: simplest whole number ratio of atoms of different elements in a compound.
Molecular formula: actual number of atoms of different elements in a compound.
Limiting reagent: determines amount of product formed. It is the product that is limited in quantity.
Excess reagent: more mols, or higher/excess amount of reagent than the reaction requires. (See calculations)