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a base is a substance that has
a pH greater than 7

an alkali is a
 base that dissolves in water
 it forms OH ions in water

acid + metal oxide
salt + water

acid + metal hydroxide
salt + water

acid + metal carbonate
salt + carbon dioxide + water

acid + metal
salt + hydrogen

acid + metal hydrogen carbonate
salt + carbon dioxide + water

acid + metal sulphite
salt + sulphur dioxide + water

a fully balanced equation or stoichiometric equation is one that shows
the formulae of reactants and products and the relative number of particles reacting

find the compound formula of Al^3+ and S2O3^2
 Al2(S2O3)3
 notice how the charges have been switched round

an ionic equation is one where
the ions are represented separately

only ..... compounds can be represented as ions . ............................................................................................................................................................................
 ionic
 covalent substances and elements cannot be represented as ions . Also ionic solids cannot be represented as free ions because they are not free to move

how to form a ionic equation
 split all the ionic compounds into their free ions where possible
 cancel spectator ions in the equation (if the same ion appears in the reactants and products the ions cancel)

percentage of an element =
 Ar of an element x number of atoms of that element in the compound
  x100
 Mr of compound

how many particles does a mole contain
6.023 x 10^23

what is the definition of the avogadro constant or avogadro number
 the number of atoms in 12g of carbon12
 avogadro constant  the total number of particles in a mole of substance also called the avogadro number it is numerically equal to 6.023 x 10^23

mole
a quantity of a substance that contains the avogadro number of particles (e.g. atoms , molecules , ions)


one mole of entity has a mass in grams equal to its Ar or Mr and contains 6.023 x 10^23 . this mass is known as
molar mass

how to calculate the number of atoms in an entity
 1) Ar or Mr
 2) number of moles (mass/Mr or Ar)
 3) number of moles x avogadros constant (we get number of molecules which is equal to molar mass)
 4) number of molecules x number of atoms

one atom of hydrogen 1 weighs 1.673 x 10^24 what's the molar mass
 stage 2
 number of moles = mass/mr
 number of moles = 1.673 x 10^24/1
 number of moles = 1.673 x 10^24
 stage 3
 1.673 x 10^24 x 6.023 x 10^23 = 0.986 g (3sf)

how many atoms of carbon are there in 1 mole of bunchy balls . each ball has 60 atoms
 stage 3
 number of moles x avogadros constant
 1 x 6.023 x 10^23 = 6.023 x 10^23
 stage 4
 molecules x number of atoms
 6.023 x 10^23 x 60 = 3.61 g (3sf)

calculate the number of nitrate ions in 20g of alumiunium nitrate
 determine formula
 Al(NO3)3.9H2O
 stage 1
 Mr = 27+ (14 x 3) +(16 x 9) + 9((2 x 1) + 16) = 375
 stage 2
 number of moles = mass/mr
 number of moles = 20/375
 stage 3
 number of moles x avogadros number = number of molecules
 20/375 x 6.023 x 10^23
 stage 4
 number of molecules x number of nitarte ions
 20/375 x 6.023 x 10^23 x 3 = 9.64 x 10^24 (3sf)

how to calculate the number of ions in an entity
 1) Ar or Mr
 2) number of moles (mass/Mr or Ar)
 3) number of moles x avogadros constant (we get number of molecules)
 4) number of molecules x number of ions

molar mass in g
(will just be asked the mass of one mole of ......)
Ar or Mr x avogadros constant

an accurate value for the mass of one mole of hydrogen atoms is 1.0080 g give a reason why this value is different from your calculated answer
the accurate value may be an average value calculated using values of data from all isotopes

molar mass in g/mole
Mr or Ar


relationship between volume occupied by a gas and temperature
 note temperature should be measured in kelvins
 V is proportional to T as long as the pressure remains constant
 V/T = constanT
 this is Charles law

relationship between volume occupied by a gas and pressure
 the product of pressure and volume is constant as long as the temperature remains constant
 PV = constant
 this is Boyles law

the volume law  Gay Lussac's law
 the pressure is proportional to the temperature as long as the volume remains constant
 P/T = constant
 combining all the realtionships gives us the equation : PV/T = constant for a fixed volume of gas

what also affects the volume that we haven't mentioned yet
 moles
 volume is proportional to the number of moles providing the temperature and pressure is constant
 V/n = constant

combining equations again
 PV/Tn = constant
 since we have taken one mole of gas , the constant is given the R symbol and is called the gas constant . for N moles of gas we have : PV=nRT
 the value of R is 8.31Jk^1mol^1 this is given in exams
 this equation is called the ideal gas equation

when using the ideal gas equation , consistent units must be used . If you want to calculate n , the number of moles :
 P must be in Pa (Nm^2)
 V must be in m^3
 T must be in K
 R must be in JK^1mol^1

rearranging the ideal gas equation for volume
V = nRT/P

rearranging the ideal gas equation for pressure
P = nRT/V

rearranging the ideal gas equation for number of moles
n = PV/RT

rearranging the ideal gas equation for temperature
T = PV/nR


compound x is a volatile liquid . in order to determine the relative molecular mass of X , a student carried out 6 experiments . In each experiment a measured mass of X was injected into an empty 100cm^3 gas syringe maintained at a pressure of 100kPa and a temperature of 373K . in each of the experiments the volume of gas produced was measured .
apart from the loss of liquid during transfer to the gas syringe , identify one other source of error in this experiment . suggest one improvement to minimise this other source of error
 source of error = the temperature may not have constantly remained at 373K
 improvement = the experiment should be done in a water bath where the temperature is constant

