CHEM10006 Study Guide - Final Guide: Biogeochemical Cycle, Carboxyhemoglobin, Acid Strength
12 Jun 2018
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The pH of pure water depends on temperature
Carbon & life
●Carbon in atmosphere largely present as CO
2
●Carbon in living systems present in biomolecules
●In geosphere present as carbonate minerals & in
sediments
●Cycling through biogeochemical cycle: oxidation
state ranges from -4 to +4
●CO: odorless, colorless, neutral oxide, product of
incomplete combustion of fossil fuels, triple bond, a
ligand for Fe in myoglobin & haemoglobin, greater
affinity than O
2
: carboxyhemoglobin
●CO
2
: colorless, non-toxic, some odour, product of
human respiration and combustion of fossil fuels, a
greenhouse gas, soluble, dissolves to carbonic acid,
determines the pH of natural waters & blood
Acids & Bases
Water undergoes self-ionization which involves the transfer of
a proton from one water molecule to another to produce a
hydroxide ion & hydronium ion
H
2
SO
4
is a stronger acid than other acidic forms
SO
3
has trigonal geometry
Phosphorus
Bones & teeth, DNA/RNA (phosphodiester link), energy
carriers, exists in minerals, allotropes
P
4
O
10
in water creates H
3
PO
4
(phosphoric acid): weak triprotic
acid: dissociates in a stepwise manner, undergoes
polymerization reactions
Gas solubility increases with pressure e.g. O
2
& N
2
Henry’s law: The amount of gas dissolved in a solution is
directly proportional to the pressure of the gas above the
solution: K
H
is the Henry’s law constant (i.e. equilibrium
constant)
As temperature decreases, stability increases due to less
kinetic energy: less escape from a liquid as gas
C
gas
= Molarity of gas in solution
P
gas
= Partial pressure of the gas
Rearranged:
The larger the value of K
H
,
the more soluble the gas
Calculating pH of Weak Acids
Esters
●Organic esters: Formed by condensation reactions
between carboxylic acids & alcohols
●Phosphate esters: Formed by condensation reactions
between phosphoric acid & alcohols
Energy captured by
photosynthesis stored &
transferred by phosphate
molecules
Energy stored as P-O bonds,
with the forward reaction
catalysed by ATPase
enzymes & reverse by
phosphatase enzymes:
energy released for
metabolic purposes
High charge repulsion in
trophosphase partially
relieved when ATP
hydrolyzed: releases energy
Document Summary
H 2 so is a stronger acid than other acidic forms. Bones & teeth, dna/rna (phosphodiester link), energy carriers, exists in minerals, allotropes. P o 10 in water creates h 3 po 4 (phosphoric acid): weak triprotic acid: dissociates in a stepwise manner, undergoes polymerization reactions. The ph of pure water depends on temperature. Carbon in atmosphere largely present as co 2. Carbon in living systems present in biomolecules. In geosphere present as carbonate minerals & in sediments. Cycling through biogeochemical cycle: oxidation state ranges from - to + . Co: odorless, colorless, neutral oxide, product of incomplete combustion of fossil fuels, triple bond, a ligand for fe in myoglobin & haemoglobin, greater a(cid:1562)nity than o 2 : carboxyhemoglobin. Co 2 : colorless, non-toxic, some odour, product of human respiration and combustion of fossil fuels, a greenhouse gas, soluble, dissolves to carbonic acid, determines the ph of natural waters & blood.
