Zusammenfassung der Ressource
Reactions + oxidation
- Titrations
- Must know conc. of
one or two solutions
- Standard solution
- Use to find unknown info
about substance dissolved
in 2nd solution
- Unknown info may be
- Conc. of solution
- Molar mass
- Formula
- No. of
molecules of
water of
crystallisation
- Indicators
- Methyl orange
- Acid = red;
Base = yellow;
End point =
orange
- Bromothymol blue
- Acid =
yellow; Base
= blue; End
point = green
- Phenolphthalein
- Acid = colourless;
Base = pink; End
point = pale pink
- Calculating unknowns
- 1st 2 steps the same
- 1) Calculate amount, in mol, of reactant
- n = c x V/1000
- 2) Calculate amount, in mol, of other reactant
- Stoichiometry
- 3rd step different
- Unknown conc.
- Calculate conc. of unknown
- c = nx1000 / V
- Unknown molar mass
- Calculate molar
mass of unknown
- M = n x m
- Oxidation number
- Number of electrons
an atom uses to bond
with atoms of other
elements
- Rules
- Uncombined element = 0
- Combined oxygen = -2
- When combined with fluorine
= +2, in peroxides = -1
- Combined hydrogen = +1
- When bonded
to metal in
hydrides = -1
- Simple ion = charge on ion
- Combined fluorine = -1
- Some elements form compounds
and ions in which the element
has different oxidation no's
- Use Roman Numerals
- Transition elements
form ions with different
oxidation no's.
- Oxyanions = negative
ions that contain an
element with oxygen
- End in -ate
- Redox reactions
- Substance that is reduced
takes electrons form
substance that is oxidised
- Half equations show how electrons are transferred
- Metals = oxidised - lose electrons -> +ve ions
- Non-metals = reduced - gain electrons -> -ve ions
- Reduction =
decrease in oxidation
no. oxidation =
increase
- Metals and acids
- Metal =
oxidised -. +ve
metal ions
- Hydrogen =
reduced ->
hydrogen gas
- metal + acid -> salt + H2