In the test for cl1- and so4 2- , explain why the addition of acid will dissolve or decompose other silver salts and barium salts, which otherwise might interfere

Strong acids can dissolve the salts of weak acid. When we consider the different salts of silver:

Salts of silver with the conjugate bases of a weak acid are soluble in strong acidic solutions. Some of these salts are:

Salts of silver with the conjugate bases of a strong acid are not affected by change in pH:

These two salts with Chloride and sulfate ions are not soluble in acidic solutions as the salts of silver with the conjugate bases of a strong acid are not soluble in acidic solutions, they remain unaffected by any change in pH.

So for salts of Ag and Ba with the conjugate bases of a weak acid, solubility is increased upon the addition of an acid. So, the interference from the ions of weak acids can be removed by decreasing the pH.

  the   balanced   equation   for   reaction of   ca metal   with   o2 to   produce   cao   is as below

2 ca+ o2→ 2 cao2

  explanation

the reaction is   balanced     since the   number of atoms   in reactant side is   equal to   number of atoms   in   product side.   for   example   they   are 2   atom of   ca in   reactant   side   and   2   atoms of ca   in   the product side.

  the   process   is a   meet the   requirement   of   redox   reaction because :     calcium   is   oxidized   from   oxidation state 0   to 2+   while   oxygen   is reduced from   oxidation   state   0   to 2-