Semiconductors can become conductive if their temperature is raised sufficiently to populate the (empty) conduction band from the highest filled levels in the valence band. The ratio of the populations in the highest level of the conduction band to that of the lowest level in the valence band is

Which statement about hf is true? it is zero for any compound in its standard state. it is positive when the bonds of the product store more energy than those of the reactants. it is negative when a compound forms from elements in their standard states. it is zero for any element that is in the liquid state.

Rays from the sun are not considered matter true or false

To prevent the presence of air, noble gases are placed over highly reactive chemicals to act as inert "blanketing" gases. a chemical engineer places a mixture of noble gases consisting of 4.37 g of he, 13.36 g of ne, and 36.65 g of kr in a piston-cylinder assembly at stp. calculate the partial pressure in torr of kr.