91. Lead(II) oxide is obtained by roasting galena, lead() sulfide, in air. The unbalanced equation is:

PLS(s) + 0,(g) PbO(s) + SO,(g)

a. Balance the equation, and determine the

theoretical yield of PbO if 200. 0 g of PbS is

heated

b. What is the percent yield if 170. 0 g of PbO is

obtained?

The items in the following list are all units of matter. which is the smallest unit that retains the properties of the matter? a.) atom b.) compound c.) electron d.) element

People with normal vision cannot focus their eyes underwater if they aren't wearing a face mask or goggles and there is water in contact with their eyes. in a simplified model of the human eye, the aqueous and vitreous humors and the lens all have a refractive index of 1.40, and all the refraction occurs at the cornea, whose vertex is 2.60 cm from the retina.with the simplified model of the eye, what corrective lens (specified by focal length as measured in air) would be needed to enable a person underwater to focus an infinitely distant object? (be careful-the focal length of a lens underwater is not the same as in air! assume that the corrective lens has a refractive index of 1.62 and that the lens is used in eyeglasses, not goggles, so there is water on both sides of the lens. assume that the eyeglasses are 2.05cm in front of the eye.)

You have 80 g of 60oc water and 80 g or 10oc water. what is the final temperature when the two are mixed? explain.