Amount Of Substance Flashcards
Empirical Formula
Divide the mass percentage by its mass number
Divide by the smallest number
Simplify the ratio
Water of Crystallisation
compound.xH20
E.g hydrated copper sulphate - CuSO4.5H2O
Anhydrous copper sulphate - CuSO4
Use empirical formula to work out
Moles equation
Mass = Mr x moles
Limiting Reactant + Excess equation
Mass = Mr x moles
Actual mass divided by theoretical mass = decimal x100
= % yield
Percentage error equation
+-n / quantity measured (x100)
Percentage atom economy equation
Mr of desired product / total Mr of reactants x100
Concentration and density Equation
Concentration = moles/volume
Density = mass/volume
Conversions from moldm-3 to gdm-3
Moldm-3 —> gdm-3 is /Mr
Gdm-3 —> Moldm-3 is xMr
How to do a titration calculation
May need to convert between cm^3 and dm^3
Find the moles of the known substance
Find the ratio
Use the moles and the given volume to find concentration
Concentration = mol/vol
What is the ideal gas equation
PV = nRT
How to find reacting gas volumes
Use the ratios
Use both volumes given to see if there is enough of each to be used (one will be a limiting factor)
May ask you to calculate the total volume of gas leftover in total OR each independent part
What is each component in the ideal gas equation
Pressure (kPa to Pa) x1,000
Volume (cm^3 to m^3) /1,000,000 or x10^-6
Moles
R (ideal gas constant) 8.31
Temperature (K) from C° (+273)
What are the standard conditions?
Temperature = 25°C (298K)
Pressure = 1atm (101,000 Pa or 101kPa)
C = 1moldm^-3
What is relative atomic mass?
Average mass of an atom of an element relative to one twelfth of the mass of an atom of carbon-12
What is relative molecular mass?
The average mass of a molecule relative to one twelfth of the mass of an atom of carbon-12
