a strong current of trivalent gaseous boron passes through a silicon crystal decreases the density of the crystal due to the part replacement of silicon by boron and due to the interstitial vacancies carried by the missing silicon atoms . in one such experiment one gram of silicon is taken and the boron atoms are found to be 1000pm by mass when the density of the silicon crystal decreases by 12%. the percentagesof missing vacancies due to silicon which are filled up by boron atoms is

Open in App

Solution

1 g Germanium------- 150 ppm = 1.5 * 10^-4 g Boron

4% decrease---- now weight is 0.96 g(Ge + B)----0.04 g missing

0.04 missing-------- (0.04-0.00015)g Ge missing------(0.04-0.00015)/72.61 moles
Ge missing=5.48810^-4 moles

Boron replaced= 1.510^-4 g = (1.510^-4)/10 moles

equivalently replaced = 3/4((1.510^-4)/10) moles of Ge ( Valency of B is 3 and
Ge is 4)

= 0.112510^-4 moles of Ge

% of Missing vacancies filled by B atoms = 0.1125100/5.488 = 2.05 %

Suggest Corrections

Similar questions

Q. A strong current of trivalent gaseous boron passed through a germanium crystal decreases the density of the crystal due to part replacement of germanium by boron and due to interstitial vacancies created by missing Ge atoms. In one such experiment, one gram 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 germanium which are filled up by boron atoms. Atomic weight of Ge

= 72.6

amu and

B = 11

amu.

Q. Estimate the proportion of boron impurity which will increase the conductivity of a pure silicon sample by a factor of

100

. Assume that each boron atom creates a hole, and the concentration of holes in pure silicon at the same temperature is

7 \times 10^{15}

holes per cubic meter. Density of silicon is

5 \times 10^{28}

atoms per cubic meter.

Estimate the proportion of boron impurity which will increase the conductivity of a pure silicon sample by a factor of 100. Assume that each boron atom creates a hole and the concentration of holes in pure silicon at the same temperature is $7 \times 10^{15}$ holes per cubic metre. Density of silicon is $5 \times 10^{28}$ atoms per cubic metre.

Q. Boron and silicon resemble chemically. This is due to the equal value of their:

Q. Oxides of boron and silicon can be reduced by _____________.

Join BYJU'S Learning Program