Balancing the reaction equation for the oxidation of lead(II) sulfide with ozone
This is a semi-standard example of why 'naive' balancing does not work.

Ozone is a source of atomic oxygen, producing free oxygen molecules. So, in 'mild' conditions only one oxygen per ozone molecule would react as a strong oxidizer, and the remaining molecular oxygen would require elevated temperatures to react. Thus the equation would be

$\ce{PbS + 4O3 -&gt; PbSO4 + 4 O2}$ 

Similarly, in excess of reducer at elevated temperature (though why would you want it with ozone is another matter) all atoms in ozone would react. Thus, the reaction should be

$\ce{3PbS + 4O3 -&gt; 3PbSO4 }$