Page 130 - [B._MURPHY,_C._MURPHY,_B._HATHAWAY]_A_working_meth

114 Chapter 8
However, an examination of the equation for the reaction shows
that the rates of these four changes are not equivalent, but are related
to uA, uB, uc and UD respectively, i.e. the stoichiometry factors of the
reaction. It can be seen in the above example, that B is consumed four
times as fast as A, i.e. 1 mole of A consumes 4 moles of B, and this in
turn is related to the rate of formation of C and D respectively, i.e.:

In general, the rate of a chemical reaction:
VAA + UBB + . . . + VCC + UDD + . . .
can be expressed as:

1 d[JI
or f-- as a general formula.
UJ dt

RATE LAW
This is the algebraic statement of the dependence of a chemical
reaction on the concentrations of a number of species, normally the
reactants. Consider the reaction:
A+B-+C

where uA = 1, VB = 1 anduc = 1.

ld[C]
Rate= ---= ld[B] +--
ld[A] ---=
1 dt 1 dt 1 dt
where -d[A]/dt o( [A] and -d[A]/dt oc [B]

Rate = --- d[A1 oc [A][B]
1 dt
Rate = d[A1 = k[A][B]
1 dt

i.e. Rate = k[A][B], where k, the constant of proportionality, is known
as the specijic rute constant. Such an equation is an example of the rate
law of a reaction, or more specifically, the experimental rate equation.