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Chemical Reactions BIOB111 Session 3 (Chemical reaction types…
Chemical
Reactions
BIOB111
Session 3
Physical
change
change in state of matter
chemical identity and composition do not change
Chemical
change
change in the chemical composition
molecular structure or the original substance changes (
REACTANT
), forming one or more new substances (
PRODUCT
)
properties of the original and new substances will also change
bonds between atoms in the reactants are broken, atoms are rearranged, new bonds are formed between atoms = products
Chemical reaction
types
Displacement
an atom or a molecule displaces another atom or group of atoms from a compound
x + yz → y + xz
Decomposition
a single reactant is broken down into 2/more simpler products (element or compound)
xy → x + y
Exchange
2 substances exchange parts of one another and form 2 different substances
ax + by → ay + bx
Combination
2/more reactants (element or compound) combine to form a single product
x + y → xy
Combustion
occurs when a substance reacts with oxygen, producing energy (heat/light)
a form of redox reaction
Chemical Equation
Reactants
on the left
Products
on the right
Law of Conservation of Matter
chemical equations must satisfy this law
atoms can neither be created nor destroyed, only rearranged
chemical equations need to be
balanced
Subscripts
identifies the number of atoms of a certain element present in a specific molecule
never change in the formula
Coefficients
identifies the number of molecules present in the specific chemical equation
always written in front of the formula
Polyatomic
ions
when balancing equations consider these ions as as unit that remain together as a unit - remains the same on either side of the equation
use brackets
REDOX
reactions
OIL RIG
Oxidation
O
xidation
I
s
L
oss of Electrons (
OIL
)
either: loss of electrons, loss of H atoms, gain of O atoms
Reduction
R
eduction
I
s
G
ain of Electrons (
RIG
)
either: gain of electrons, gain of H atoms, loss of O atoms
are
complementary
processes which run
simaltaneously
if there is a loss of electrons (oxidation), these electrons must be accepted somewhere else (reduction)
Oxidising agent
the substance that is reduced and gains electrons
#
Reducing agent
the substance that is oxidised and loses electrons
#
REDOX in
Biochemistry
Biological
oxidation
involves loss of electrons and hydrogen atoms
coenzymes transfer hydrogen atoms to another compound
coenzymes are derived from vitamins (NAD+, NADP, FAD)
Biological
reduction
addition of electrons and hydrogen atoms
molecules that undergo reduction become more energy rich
