PHYSICAL CHEMISTRY IN BRIEF

CHAP. 8: CHEMICAL EQUILIBRIUM [CONTENTS] 228

8.2 Systems with one chemical reaction

8.2.1 General record of a chemical reaction

In chemistry it is usual to record a chemical reaction as follows [see5.1]:

aA(f) +bB(f) +.. .=sS(f) +tT(f) +... (8.1)

In this record, A, B,... represent the initial chemical individuals or reactants; S, T,

... represent theproductsof a given chemical reaction;a, b,... , ands, t,... represent the
respective stoichiometric number. By subtracting the left side in equation (8.1) we obtain an
alternative record
0 =

∑k

i=1

νiRi(f). (8.2)

S Symbols:Here the chemical individuals are denoted R 1 ,... , Rn(in the first case they are denoted
A, B,... , S, T,... ), and the stoichiometric numbers are denotedνiwhere “i” is the ordinal
number of thei-th substance (in the first case they are indicated by the symbol of the substance
to which they relate). The stoichiometric numbers of the products are positive while those of
the reactants are negative.
The physical state (phase) of a given component is denoted (f). If (f) = (s), the component
is solid, if (f) = (l), it is liquid, and if (f) = (g), it is gas.

Example

Record the chemical reaction

SO 2 (g) +

1

2

O 2 (g) =SO 3 (g)

in the alternative way and calculate individual stoichiometric numbers.