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A freshly cut piece of sodium metal appe...

A freshly cut piece of sodium metal appear shiny but its metallic iustre soon gets tarnished when exposed to air. Give reason.

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When a freshly cut piece of metallic sodium is exposed to moist air, it readily reacts with oxygen to form sodium monoxide `(Na_2O)`. The resultant sodium monoxide and also the metal itself readily react with the moisture of air to form sodium hydroxide (NaOH). In the subsequent step, both `Na_2O` and NaOH combine with `CO_2` of air to form sodium carbonate `(Na_2CO_3)`. Thus, a coating of sodium carbonate is formed on the surface of the metal and as result of this the metallic lustre is tarnished.
`4Na + O_2 to 2Na_2O , Na_2O + H_2O to 2NaOH`
`2Na + 2H_2O to 2NaOH + H_2 uarr, Na_2O + CO_2 to Na_2CO_3`
`2NaOH +CO_2 to Na_2CO_3+ H_2O`
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CHHAYA PUBLICATION-s-BLOCK ELEMENTS -QUESTION-ANSWER ZONE FOR BOARD EXAMINATION (SHORT ANSWER TYPE)
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