Hydrogen ion
H+
Ammonium ion
NH4 +
Silver ion
Ag +
Hydroxide ion
OH -
Nitrate ion
NO3 -
Carbonate ion
CO3 2-
Sulfate ion
SO4 2-
Dichromate (VI) ion
Cr2O7 2-
Phosphate ion
PO4 3-
Hydrogen
H2
Fluorine
F2
Chlorine
Cl2
Bromine
Br2
Iodine
I2
Oxygen
O2
Nitrogen
N2
Methane
CH4
Ammonia
NH3
Sulphur dioxide
SO2
Nitrogen monoxide
NO
Nitrogen dioxide
NO2
Carbon monoxide
CO
Carbon dioxide
CO2
Metal + acid
Salt + hydrogen
Metal + water
Metal hydroxide + hydrogen
Metal oxide + acid
Salt + water
Metal carbonate + acid
Salt + water + carbon dioxide
Ammonia + acid
Ammonium salt
Metal carbonate
Metal oxide + carbon dioxide
Hydrochloric acid forms
Metal chloride salts
Hydrochloric acid
HCL
Nitric acid forms
Metal nitrate salts
Nitric acid
HNO3
Sulphuric acid
H2SO4
Sulphuric acid forms
Metal sulfate salts
Phosphoric acid forms
Metal phosphate salts
Phosphoric acid
H3PO4
What happens when a base react with an acid?
A salt is formed where the hydrogen ions in the acid are replaced with metal ions from the base
What are spectator ions?
Ions which watch the reaction happening without reacting themselves
Precipitates are __ in water
Insoluble
Definition of molecular formula
Actual number of atoms of each element in a compound
Definition of empirical formula
Simplest whole number ratio of atoms of each element in the compound
What's a limiting reactant?
The reactant that's completely used up so the reaction can no longer continue
What's the reactant called that's not completely used?
Excess
Definition of the mole
One mole of any substance contains the same number of particles as there are atoms in 12 g of ¹²C
What's the ar of an atom or Mr of a molecule equal to?
The mass of one mole of that substance in grams
Moles =
Mass/Mr
Concentration =
Moles/volume
1dm³ =
1000 cm³
Number of particles =
Moles of substance x Avogadro's constant
How would you make a standard solution?
Way out desired amount of solid in a weighing bottle using the two decimal place mass balance
Transfer solid to a beaker and rewe the bottle to calculate the precise mass of solid transferred
Add approximately 100 cm³ of distilled water to the beaker and use a glass rod to stir the contents until all the solid has dissolved
Use a funnel to transfer the solution into a 250 cm³ volumetric flask and then use a wash bottle to rinse the beaker and glass rod into the same volumetric flask
Use wash bottle to carefully make-up solution to mark on volumetric flask. Use a pipette near the mark to make sure you don't overshoot
Stopper the flask and invert several times thoroughly
Describe a titration method
Rinse equipment (burette with acid, pipette with alkali, conical flask with distilled water)
Pipette 25cm³ of alkali into the conical flask whilst using a pipette filler and glass pipette
Touch the surface of the alkali with the pipette (to ensure correct amount is added)
Add a few drops of indicator to conical flask and record colour
Use funnel to add acid to burette, ensuring jet space is filled with acid and note down the volume of the burette
Place white tile under conical flask to help observe colour change
Add acid to alkali whilst swirling mixture and add dripwise near end point
Note burette reading once end point has been reached
Repeat titration until obtain at least 2 concordant results
What are concordant results?
Results within 0.1cm³ of each other
Titrations:
Why use a conical flask instead of a beaker?
Easier to swirl mixture without it spilling out
Give 2 common indicators
Phenolphthalein
Methyl orange
Pink in acid, colourless in alkali
End point when colour disappears
Red in acid, yellow in alkali
End point is orange
Why is distilled water used to wash the side of the flask and does it affect the readings?
To ensure all the acid is washed into the reaction mixture to react with the alkali
No as water doesn't react with the reagents or change the number of moles of acid used
What are common burette mistakes?
Leaving funnel in burette during titration
Leaving air bubbles in jet space
Not rinsing burette before use
Why must you ensure the jet space if filled and there are no air bubbles?
If not filled properly at start, titre reading will be larger than expected as will fill the air space at first so not all solution goes into the conical flask
Why must you not leave the funnel in the burette?
Small drops of liquid may drop into solution from funnel during titration which would give a false burette reading (volume would be lower than actual volume used)
Why must the burette be rinsed with the substance that will be put in it before used?
If not, substance may be diluted by residual water in the burette or may react with a substance left from a previous titration
1000cm³ =
1dm³
1l =
When calculating titre, what result must you use?
Only concordant results
How do you record you results following a titration?
In table containing initial and final burette readings and titre
How do you work out a back titration?
Use conc and avg titre to calculate moles of base
Use equ and ratios to determine moles of reacted acid in sample
Scale up to find moles of unreacted acid in volumetric flask
Use vol and conc of acid to find moles of acid in original reaction
Calc moles of acid that have reacted, use equ and ratios to find moles, find Mr of base
Why do all measurements have uncertainties?
Due to sensitivity of equipment
%uncertainty =
(Uncertainty/measurement made on apparatus) x100
State the ideal gas equation
PV = nRT
P =
Pressure in Pa
V=
Volume in m³
R =
8.31
T=
Temp in K
kPa→Pa
X1000
cm³ →m³
X10–⁶
dm³→m³
X10-³
°C →K
+273
How do you reduce uncertainty of equipment without changing the apparatus?
Increase value of measurement
How do you increase the uncertainty of a burette?
Increase conc substance in conical flask
Decrease conc of substance in burette
How does increase conc substance in conical flask reduce uncertainty of a burette?
Would need larger volume added from burette to reach end point
Whys %yield important?
As want to get as much product as possible
What does efficient conversion of reactants to products do?
Maximises profit
%yield =
(actual yield/theoretical yield) x100
Give reasons why %yield isn't always 100%
Incomplete reactions
Losses during purification process
Losses during transfers of substances
Side reactions (forming other products)
What does %yield give info about?
How wasteful a process is
What's atom economy?
Measure of the proportion of the reactant atoms that become part of the desired product in the balanced chemical equation
%atom economy
(mass of useful products/mass of all reactants)x100
Why do industries try to use processes with high atom economy?
Better for environment as produce less waste. Waste produced needs to be disposed of safely (expensive) so less produced, the better
Why do industries use atom economy?
Try to use processes with high atom economy as better for environment and cheaper so more profit
The higher the atom economy…
The more efficient the use of raw materials, which makes the process more sustainable
Why is a higher atom economy less expensive/more profitable?
Have to spend less on seperating the desired product and less on treating the waste
Atomic number =
Number of protons
Mass number =
Total number of protons and neutrons
Neutrons = mass - atomic
Relative charge of a proton
+1
Relative charge of an electron
-1
Relative charge of a neutron
0
Relative mass of a proton
1
Relative mass of an electron
1/1800
Relative mass of a neutron
On negative ions, what's the negative charge?
The number of extra electrons
On a positive ion, what's the positive charge?
Number of electrons lost
How to calculate %purity?
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