Chem test chloride plz help!!!

"Excess" means "more than sufficient".

In this test, silver nitrate is used to form a white precipitate of silverchloride. Some other anions (e.g.sulphite ion) can form white precipitates (e.g. silver sulphite) with silvernitrate solution. However, silverchloride is insoluble in nitric acid, but all other white precipitates of silversalt are soluble. Therefore, excess nitricacid is added to ensure that all other white precipitates of silver salts.

2013-10-29 16:30:39 補充：
The solubility of silver sulphate is low, but is much higher than that of silver chloride. When silver nitrate is added to a solution of sulphate salt, only a small amount of precipitate is formed. To avoid confusion, many syllabuses (like HKDSE) assume that silver sulphate is soluble in water.

其實在 DSE 的離子試驗是簡化版，初學時不必弄得太複雜。

正如不用客氣所說，silver sulphate 的溶解度雖然不高，但在 DSE 的離子試驗中可當作溶於水，不形成沉澱。

不用客氣 所說是正確的，加入硝酸 (Nitric acid) 可以防止很多其他的銀鹽，例如碳酸銀，亞硫酸銀等影响觀察結果。但其實有一個例外，它是硫酸銀，硫酸銀不溶於硝酸，硫酸銀也是白色ppt.，硫酸銀的溶解度比氯化銀更細，點好呢？曬太陽啦！氯化銀會變黑但硫酸銀唔會。


例如你在 test tube 中加入小小樣本 ( 1 cm )高，加入 5 cm 高硝酸就叫做 excess。


在這點，不用客氣 所說是的很正確。

2013-11-10 00:33:21 補充：
紙上談兵當然怎樣都可以，在實驗室見到就會好痛苦啦！

Excess means more than required, it is used to see if the precipitate is soluble or insoluble.