CHEM 120 Lecture Notes - Lecture 21: Bromothymol Blue
15 Jun 2018
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Neutralization: all the base is used up, producing the same amount of conj. base as lost by initial
acid
Equivalence Point: all your initial acid has been converted to conj. base by neutralization
Acid-Base Indicator: weak organic acid/base which the ionized and un-ionized forms are different
colours
- pH < 6.1 yellow, pH ~ 7.1 green, pH > 8.1 blue
- End-point: when the indicator changes colour (SLIDE)
Choosing an Indicator: Strong A&B → bromothymol blue, chlorophenol red & phenol red
CH.19 – ELECTROCHEMISTRY
Oxidizing Agent – substance takes electrons
Reducing Agent – substance that supplies electrons
https://www.kijiji.ca/v-appartement-condo-studio-1-1-2/ville-de-montreal/berri-uqam-metro-
station-superb-new-studios-a-loeur/1320635938Oxidizing State: charge an atom would have if all
bonds are ionic
- Double Displacement reactions are NOT redox reactions, no change in oxidation #
Balanced Redox; # electrons lost = # electrons gained
Half Reaction Method:
1) Assign oxidation #
2) Write the reaction as 2 half-reactions → oxidation + reduction
3) Balance the half reactions for mass; all atoms except H & O balance both by adding H+ &
H2O, only include ions that change oxidation state
4) Add electrons to balance charge
5) Ensure both reactions have equal #s of electrons
6) Add the half reactions to get the overall reaction
7) Check that the mass & charge balance and all electrons cancel
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CHEM 120 Full Course Notes
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Document Summary
Neutralization: all the base is used up, producing the same amount of conj. base as lost by initial acid. Equivalence point: all your initial acid has been converted to conj. base by neutralization. Acid-base indicator: weak organic acid/base which the ionized and un-ionized forms are different colours. Ph < 6. 1 yellow, ph ~ 7. 1 green, ph > 8. 1 blue. End-point: when the indicator changes colour (slide) Choosing an indicator: strong a&b bromothymol blue, chlorophenol red & phenol red. Reducing agent substance that supplies electrons https://www. kijiji. ca/v-appartement-condo-studio-1-1-2/ville-de-montreal/berri-uqam-metro- station-superb-new-studios-a-loeur/1320635938oxidizing state: charge an atom would have if all bonds are ionic. Double displacement reactions are not redox reactions, no change in oxidation # Balanced redox; # electrons lost = # electrons gained. Half reaction method: assign oxidation , write the reaction as 2 half-reactions oxidation + reduction, balance the half reactions for mass; all atoms except h & o balance both by adding h+ &
