In the manufacture of microelectronic devices, a thin film of solid silicon ( Si ) is uniformly deposited on a wafer surface by the chemical decomposition of silane \left(\mathrm{SiH}_{4}\right) in the presence of \mathrm{H}_{2} gas. If the gas composition is maintained at 40 \mathrm{~mol} \% \mathrm{SiH}_{4} and 60 \mathrm{~mol} \% \mathrm{H}_{2}, determine
a. the weight fraction of these species;
b. the average molecular weight of the gas mixture;
c. the molar concentration, c_{\mathrm{A}}, of \mathrm{SiH}_{4} if the feed gas is maintained at 900 K and a system pressure of 60 torr.
Passo 1
O enunciado dá uma mistura gasosa ideal contendo silano \mathrm{SiH}_{4} e hidrogênio \mathrm{H}_{2} com frações molares y_{\mathrm{SiH}_4}=0,40 e y_{\mathrm{H}_2}=0,60. Pede-se:
– (a) as frações mássicas;
– (b) o peso molecular médio da mistura;
– (c) a concentração molar c_{\mathrm{SiH}_4} a T=900\\ \mathrm{K} e P=60\\ \mathrm{torr}.
Conteúdo: balanço de massa para misturas, definição de peso molecular médio e lei dos gases ideais.