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Question
Metals X and Y can be recovered from the anode mud left behind after the electrolytic refining of copper metal. The coins made of metal X look new even after several years of use but the coins made of metal Y lose their shine gradually and get blackened soon. When metal X is alloyed with a small amount of metal Y, it becomes hard and hence suitable for making ornaments. What are metals X and Y? Also state the colour of metal X.
Solution
Metals X and Y are gold and silver, respectively. They can be recovered from the anode mud that is left behind after the electrolytic refining of copper metal. The coins made of metal X (gold) look new even after several years of use because gold is the least reactive metal and it does not react with air, water, acids, alkalis etc. On the other hand, coins made of metal Y (silver) lose their shine gradually and get blackened soon because silver reacts with hydrogen sulphide gas in the air and forms a thin black layer of silver sulphide (Ag2S) on it.
When metal X (gold) is alloyed with a small amount of metal Y (silver), it becomes hard and suitable for making ornaments. Pure gold is very soft and cannot be used for making ornaments. However, when it is mixed with silver, it becomes hard and suitable for making ornaments.
The colour of metal X (gold) is yellow.
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