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A strong current of trivalent gaseous boron passed through a germanium crystaldecreases the density of the crystal due to part replacement of germanium by boron and due to interstital vacancies created by missing Ge atoms . In one such experiment , 1g of germanium is taken and the boron atoms are found to be 150 ppm by weight , when the density of the Ge crystal decreases by 4 % . calculate the percentage of missing vacancies due to germination , which are filled up by boron atoms . (Awof Ge = 72.6 and B = 11 ) (assume volume constant )

Answer» <html><body><p>`23%`<br/>`2.3%`<br/>`<a href="https://interviewquestions.tuteehub.com/tag/46-317673" style="font-weight:bold;" target="_blank" title="Click to know more about 46">46</a>%`<br/>`80%`</p>Solution :Assume here that the decrease in density is not <a href="https://interviewquestions.tuteehub.com/tag/due-433472" style="font-weight:bold;" target="_blank" title="Click to know more about DUE">DUE</a> to volume change but due to loss of Ge <a href="https://interviewquestions.tuteehub.com/tag/atoms-887421" style="font-weight:bold;" target="_blank" title="Click to know more about ATOMS">ATOMS</a> only. Let x be the tota numberof Ge atoms missing and y be the number of B atoms <a href="https://interviewquestions.tuteehub.com/tag/replacing-2248205" style="font-weight:bold;" target="_blank" title="Click to know more about REPLACING">REPLACING</a> Ge atoms. Assuming the volumne of crystal reamining saem, than 4% decrease in density will also decrease weight of the crstal (sample) by 4%. <br/> `therefore 1-(x xx(72.<a href="https://interviewquestions.tuteehub.com/tag/6-327005" style="font-weight:bold;" target="_blank" title="Click to know more about 6">6</a>)/(N_(A)))+(y xx(11)/(N_(A)))=0.96` <br/> `0.04=(x xx(72.6)/(N_(A)))-(y xx (11)/(N_(A)))` <br/> `y=((150N_(A))/(10^(6)xx11)xx0.96)` or `(yxx11)/(N_(A))=((150xx0.96)/(10^(6)))` <br/> `thereforex=((0.04+1.44xx10^(-4))N_(A))/(72.6)=(0.04N_(A))/(72.6)` <br/>`therefore(y)/(x)=(150N_(A)xx0.96xx72.6)/(10^(6)xx11xx0.04N_(A))=2.376xx10^(-2)` <br/> `therefore (y)/(x)xx100=2.376xx10^(-2)xx100=2.376%`</body></html>


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