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1. A substance X, which is an oxide of a group \(2\) element, is used intensively in the cement industry. This element is present in bones also. On treatment with water it forms a solution which turns red litmus blue. Identify X and also write the chemical reactions involved.
The given substance X is . Calcium oxide is used intensively in the cement industry. The element present in bones also is calcium. Calcium oxide mixed with water forms a solution of (\(Ca(OH)_2\)), which is an alkali. As a result, it turns red litmus blue.
The chemcal equation of the above finding is \(2CaO\)(s) + \(H_2O\)(l) → \(Ca(OH)_2\)(aq).
2. A silver article generally turns black when kept in the open for a few days. The article when rubbed with toothpaste again starts shining.Why do silver articles turn black when kept in the open for a few days? Name the phenomenon involved.
The silver article turns black when kept in the air because the silver article reacts with sulphur compounds such as (\(H_2S\)) present in the air.
\(Ag\) + \(H_2S\) → \(Ag_2S\) + \(H_2\)
The phenomenon is called corrosion. It is called .
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