Question

Copper and brass vessels are cleaned with the lemon
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Answer 1

Explanation:

Citric acid in lemon juice etches away copper oxide that gives the vessels the dark color. When the oxide is removed, the copper metal underneath is exposed, it has a common ph range of 2-3 and reacts with metals and serves as a good cleaning fluid for metallic surfaces.

Answer 2

Answer:

bcoz they develop a layer over them when left in air

Explanation:

for example when copper is left in air it develops a layer of copper carbonate which is basic in nature so we apply lemon to neutralize its basicity