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Chemical Reactions and Equations — Science STD 10 — Question

CBSE BoardEnglish MediumSTD 10ScienceChemical Reactions and Equations3 Marks
Question
A silver article generally turns black when kept in the open for a few days. The article when rubbed with toothpaste again starts shining.
  1. Why do silver articles turn black when kept in the open for a few days? Name the phenomenon involved.
  2. Name the black substance formed and give its chemical formula.
✓

Answer

1. Metals such as silver when attacked by substances around it such as moisture, acids, gases etc, are said to corrode and this phenomenon is called corrosion.
2. The black substance is formed because silver (Ag) reacts with $H _2 S$ present in air. It forms thin black coating of silver sulphide $\left( Ag _2 S\right)$.

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