Amount Of Substance Flashcards
What is relative atomic mass
The relative atomic mass, Ar, is the weighed average mass of an atom of an element taking into account its naturally occurring isotopes, relative to 1/12th the relative atomic mass of an atom of carbon 12
What is the formula to work out the relative atomic mass
Average mass of one atom X 12
What is the relative molecular mass
The relative molecular mass, Mr, of a molecule is the mass of that molecule compared to 1/12th the remit I’ve atomic mass of an atom of carbon - 12
How do you find the relative molecular mass
By adding up all of the trait I’ve atomic masses of the atoms present in the molecule
What is relative formula mass used for ??
Ionic compounds
What is the definition for the Avogadro constant or Avogadro number
It is the number of atoms in 12g of carbon - 12
What is the Avogadro constant written as
6.022 X10(23)
What is a mole
The amount of a substance that contains 6.022X10(23) particles
What is the formula to find out the number of moles present using Mr and mass
Number of moles = mass (g) devided by the Mr
What is the ideal gas equation
PV=nRT
In the ideal gas equation what must be used as the unit for pressure
Pa
Nm-2
In the ideal gas equation what must be used as the unit for volume
M3
Metres cubed
In the ideal gas equation what must be used as the unit for temperature
K
Kelvins
In the ideal gas equation what is the unit of R
- 31
8. 31JK-1 mol-1
How do you convert from the volume unit dm3 to m3
Dm3
—
How do you convert from the volume unit cm3 to m3
Cm3
—
How do you convert from the unit of pressure kpa to pa
Kpa X 1000 = pa
How do you convert from the pressure unit mpa to pa
MPa X 1000000 = pa
How do you convert from the temperature unit degrees to kelvins
^C + 273 = K
How do you find out the number of moles using the consecration and volume
C x V
How do you work out the apparatus uncertainty
Error intervals decided by measurement
How many particles does one mole contain
6.02x1023
What is the formula for the number of particles
Number of particles = number of moles x Avogadro’s constant
What mass of sodium hydroxide (NaOH) needs to be dellolved in water to give 50 cm3 of a solution with a concentration or 2 Moldm-3 ?
Discribe the steps to work this out
1) converts the volume to dm3 (50/1000 = 0.5 dm3)
2) work out the number of moles of NaOH (2 mol dm x 0.05 dm3 = 0.1 )
3) work out the Mr of NaOH (23 + 16 + 1 = 40)
4) mass = number of moles x mr ( 0.1 x 40 = 4)
What are ionic equations
Equations that show only the reacting particles
What does making a standard solution involve
Dissolving a known amount of solid in a known amount of water to create a known concentration
What is a standard solution
A solution you know the exact concentration of
Describe the steps to make a standard solution
1) work out how many moles of the substance you need (m=cxv)
2) work out how many grams of substance you need(ma=molxmr)
3) weigh by measuring the beaker then beaker with solid and take away mass of the beaker
4) add distilled water to dissolve
5) pour into volumetric flask (use funnel) rising beaker and rod
6) top the flask up to the correct volume
7) add stopper and mix a bit more
What do titrations help you find out
Exactly how much acid is needed to neutralise a measured quantity of alkali (or vis versa)
How would you use a pipette to measure the volume of the solution
1) use the pipette to measure the set volume of solution
2) put in a flask
3) add a few drops of indicator
4) fill the burette with the standard solution (using a funnel)
5) take the funnel out of top of burette when finished
What are the two indicators used
Methyl orange
Phenolphthalein
What are the colours that the indicator methyl orange goes
Red in an acid and yellow in an alkali
What colours does the indicator phenolphthalein go
Colourless in acid
Pink in alkali
How do you calculate the concentration from a titration
1) write a balanced equation and decide what you need to know
2) work out the moles of the one you know enough info for
3) what is the ratio for the reaction if the ratio is 1:1 the moles are the same
4) work out the concentration
How would you work out the volume from a titration reaction
1) write a balanced equation
2) work out the moles of what you know
3) work out the ratio and therefor the other moles
4) work out the volume
How do you work out the empirical mass
You add together the total mass form the all the empirical formulas
How do you work out the theoretical formula
Theoretical yeald = moles x mr
What is the percentage yeald formula
Actual yield dividied by the theoretical yield times 100
What is the atom economy formula
Molecular mass of desired product divided by the mass of atoms in reactions times 100
Explain what equation you would do.
Calculate the mass in kg, of a single 52Cr ion assume that the mass of the 52Cr+ is n is the same as that of a 52Cr atom
(Avogadro constant = 6.022X10(-26))
(52/ 1000) divided by the Avogadro constant
