Calculations Flashcards
Formula moles ( concentration )
Moles = vol ( dm3) x conc. ( moldm-3)
Formula moles ( mass )
Moles = mass / Mr
massive Mr mole
Cm3 to dm3
/1000
dm3 to cm3
x1000
How many particles does 1 mole of a substance contain
6.02 x 10 ^23
What is Avogadro’s number
6.02 x 10^23
Formula for no. of particles, atoms, or molecules
Moles x Avogadro’s number
= moles x ( 6.02 x 10^23 )
What is Avogadro’s constant
6.02 x 10^23 mol-1
Formula for calculating chemical %
( Ar / Mr ) x 100
Eg. ( C / CO2 ) x 100
= % of carbon in carbon dioxide
Formula for % yield
% yield = ( actual yield (g) / theoretical yield (g) ) x 100
How to work out relative atomic mass ( Ar ) ( of isotopes )
- Multiply mass of each isotope by relative abundance
- Add them together
- Divide by sum of relative abundance’s
When will you have to work out the relative atomic masses of isotopes
From a Mass Spectrometry
When given a mass spectrometry what do u have to work out
The relative atomic mass from isotopes and there abundances
what does emitting an alpha particle ( helium atom ) do to the atomic no. and mass no.
Mass no. = -4
Atomic no. = -2
what does emitting a beta particle ( electron ) do to the atomic no. and mass no.
Mass no. = stays the same
Atomic no. = +1
Reasons why actual compound mass could be less than theoretical amount
- Reversible reaction
- Product lost - when separated from reaction mixture
- Reactants may react in other reactions
Equation for c, speed of light ( spectroscopy )
c=v lamda
Speed of light = frequency x wavelength ( m )
1st equation for E, Energy (J)
Spectroscopy
E=hv
Energy = planks constant x frequency
2nd equation for E, energy (J) when only given wavelength
E= hc/ lamda
Energy (J) = ( planks constant x speed of light ) / wavelength
How to go from J -> KJmol^-1
Divide by 1000
Then…
Multiply by Avogadros constant
How to go from KJmol^-1 -> J
Divide by Avogadros constant
Then….
Multiply by 1000
How to calculate empirical formula (5)
- List all elements in compound
- Write mass/ % of each element
- Divide each element by Ar = moles
- Divide each element by smallest no. of moles
- Get ratio in simplest whole no. form ( by x or / )
In a water of crystallisation calculation what does the x stand for
Ratio moles of water
Equation for heat energy transferred ( given out / absorbed )
q=mcAT
What does each letter stand for in q= mcAT
- q= heat energy transferred ( J )
- m= mass of substance ( liquid / solution ) heated
- c = specific heat capacity ( 4.18)
- AT (delta T ) = change in temp ( in K but no conversions required )
Equation for (molar) enthalpy change ( per mole )
Delta H = q(KJ) / no. of moles reacting
