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Why do silver articles turns blackish wh...

Why do silver articles turns blackish while copper vessels turn greenish on keeping it in air for a long time ?

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(i) Copper on exposure to moist air combines with carbon dioxide and a green coloured copper carbonate salt is formed, tarnishing the copper.
(ii) Lime joice and tamarind contain citirc and tartaric aciid respectively.
(iii) These react with copper cabonate forming water- soluble salts, which get washed off easily.
(iv) Due to this, the tarnished copper becomes clean and regains its lustre.
(v) Hence, lemon or tarmarind is used for cleaning copper vessles turned greenish.
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