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1.0 g of Mg is burnt in a closed vessel which contains 0.5 g of O_2. (i) Which reactant is left in excess? (ii) Find the weight of excess reactant. (iii) How many millilitres of 0.5 N H_2 SO_4 will dissolve the residue in the vessel?

Answer» <html><body><p></p>Solution :`Mg+O_2 to MgO` <br/> Equivalent of `Mg = (1)/(12) = 0.0833""("eq. wt. of" Mg = ( "at. wt." )/( "<a href="https://interviewquestions.tuteehub.com/tag/valency-724638" style="font-weight:bold;" target="_blank" title="Click to know more about VALENCY">VALENCY</a>") = ( <a href="https://interviewquestions.tuteehub.com/tag/24-295400" style="font-weight:bold;" target="_blank" title="Click to know more about 24">24</a>)/(2) )` <br/> Equivalent of oxygen `(0.5)/( 8) = 0.0625 "(eq. wt. of O = 8)"` <br/> (i) Mg is in excess because its eq. is <a href="https://interviewquestions.tuteehub.com/tag/greater-476627" style="font-weight:bold;" target="_blank" title="Click to know more about GREATER">GREATER</a> than that of oxygen. <br/> (ii) Equivalent of Mg in excess `=0.0833 - 0.0625` <br/> `= 0.0208` <br/> `therefore` weight of Mg in excess `=` equivalent `<a href="https://interviewquestions.tuteehub.com/tag/xx-747671" style="font-weight:bold;" target="_blank" title="Click to know more about XX">XX</a>` equivalent weight <br/> `= 0.0208 xx 12 = 0.25 g` <br/> (iii) The residue contains MgO and Mg which has not taken part in the reaction. Suppose `upsilon` mL of `H_2 SO_4` is required to <a href="https://interviewquestions.tuteehub.com/tag/dissolve-432057" style="font-weight:bold;" target="_blank" title="Click to know more about DISSOLVE">DISSOLVE</a> the residue. <br/> `therefore` m.e. of `H_2 SO_4` = m.e. of Mg + m.e. of MgO (not reacted) <br/> `therefore 0.5 upsilon` = (eq. of Mg + eq. of MgO)<br/> ` = 1000` (eq. of Mg `+` eq. of O) <br/> `=1000 (0.0208 + 0.0625)` <br/> `= 83.3` <br/> `therefore upsilon= 166.6` mL.</body></html>


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