# If one litre of air is passed repeatedly over heated copper and magnesium till no further reduction in volume takes place. The volume finally obtained would be approximately  a) 800 ml b) 200 ml  c) 10 ml  d) zero Please tell how to approach these kind of questions

Dear Student,

The atmospheric air contains 1% of noble gas and the rest 99% is comprised of oxygen and nitrogen.  For example if 1 liter of air is passed (1000 ml) over Mg and Cu consumes some amount of oxygen and nitrogen  the reaction scheme formed is,

$2Cu+{O}_{2}\to 2CuO\phantom{\rule{0ex}{0ex}}3Mg+{N}_{2}\to M{g}_{3}{N}_{2}$

On repeated exposure 99% of air is consumed that is 990 ml so the rest left is of noble gas 1% of 10 ml. So by the process end with 10 ml of air volume.

Hence the answer is Option (C) 10 ml.

Regards.

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The answer i think must be (d). Its a ques of stochiometry. Write the balanced equation of oxidation of cu nd mg nd u ll get to know the answer.
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