Chemistry Question?

A 4.75g silver coin was dissolved in nitric acid and the resulting solution diluted to 250mL. When a 25.0 mL sample of 0.200 M NaCl was titrated with the silver solution, using chromate indicator, 28.8mL of silver solution was required. What was the percentage purity of the silver in the coin, assuming any impurities present were unreactive.

My real question is, why do we neglect nitric acid when writing the chemical formula? Do we only have to write the formula where precipitates occur? Therefore the formula is Ag + Cl -> AgCl.

Answer:
It does this because the problem states that the impurities were nonreactive. A lot of chemistry books use half reactions, not complete chemical reactions. I know it's confusing, and it's not helpful when they skip steps that can confuse people not familiar with chemistry. Half the reaction is Ag/Cl ion reaction, the other half of the reaction is the nitric acid turning into water, and other things. It's simple not necessary to consider the chemistry of that reaction at all, because you aren't concerned with it.

Only when the impurities aren't consider, or there isn't any electron pushing going on with the other half of reaction can you ignore it.
The nitric acid can be ignored because it takes no part in the mathematics. We are interested in the silver ion concentration, and the chloride ion concentration; the nitrate doesn't count. All that the nitrate does is to oxidize the silver so that it can go into solution.

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