Page 128 - Basic physical chemistry for the atmospheric sciences

1 1 4 Basic physical chemistry

(6. l l b)
l
Step 3. We must first balance the carbon in Reaction (6. 1 a ) by multi­
plying the left side by six

Since the overall reaction is neutral, and there are six excess oxygen
atoms on the left side, we must add six H 20(l) to the right side

Since there are now 24 excess hydrogen atoms on the right side, we
must add 24 H + (aq) ions to the left side to obtain the balanced reduc­
tion half-reaction
(6. l c )
l
To balance Reaction (6. l b ) , since there i s one excess oxygen atom
l
on the right side, we must first add one H 20(1) on the left side

There are now four excess hydrogen atoms on the left side, which can
be balanced by adding four H + (aq) to the right side
l
2H 2 0(l)- Oi(g) + 4H + (aq) (6. l d )
l
Step 4. To balance Reaction (6. l c ) electrically
l
6C02(g) + 24H + (aq) + 24e - - C 6 H 1 2 0 (s) + 6H20(l) (6. l e )
6
To balance Reaction (6. l d ) electrically
l
4
l
2H20(l)- Oi(g) + H + (aq) + 4e - (6. 1 f )
Step 5 . To make the number of electrons gained in Reaction (6. l le)
equal to the number released in Reaction (6. l lf), we multiply Reaction
(6. l f ) by six
l
(6. 1 g )
l
Step 6. Adding Reactions (6. l e ) and (6 . 1 lg) and canceling terms
l
yields

Step 7 . Inspection shows that Reaction (6. 1 2 ) conserves the various
atoms and electric charge.