A sample of n-type semiconductor is found to be an insulator at very low temperatures. As the temperature is raised, there comes a point at which the conductivity increases markedly, but after this point the conductivity remains pretty much constant as the temperature is raised further. At much higher temperatures, the conductivity starts to increase steadily, with no sign of it reaching a plateau. Explain these observations.
General Chemistry II 1516 Week 6 15.5, 4.1, 4.2, 4.3, 16.1, 16.2, 16.3, 16.4 15.5 Factors That Affect Chemical Equilibrium Le Chatelier’s Principle – when stress is applied to a system at equilibrium, the system shifts to the direction that minimizes the affect of the stress How does each of the following affect Keq 1. Addition/removal of an aqueous/gaseous product or reactant 2. Change in volume 3. Change in temperature 1 and 2 do not affect Keq, but 3 does affect it The reaction direction DOES shift with addition of removal depending how Q shifts. Addition of reactant = shift right Removal of reactant = shift left Addition of product = shift left Removal of product = shift right Ex. H 2I 22HI H Add 2 = shift right H Remove 2 = shift left Add HI = shift left Remove HI = shift right If you are adding a solid or liquid, no change occurs. Change in volume or pressure: Decrease in volume increases concentration Increasing pressure (volume decrease) shifts the reaction to the side with the fewest gas molecules Decreasing pressure (volume increase) shifts the reaction to the side with the most gas molecules If the pressure is changed by the addition of an inert gas (ex. Helium), there is no affect on equilibrium Ex. What direction does the reaction shift with a decrease in volume Hint: look for the side with the fewest gas molecules a. PCl 5(g)PCl 3(g)Cl
