The walls in your home have 25mm of expanded polystyrene (R-value 3.96) and 25mm of rigid urethane foam (R-value 7.50). What is the R-value of your insulation?

How many moles are in 1.26*10^24 particles in significant figures

Large crystals are formed when igneous rocks cool very slowly igneous rocks cool very quickly sedimentary rock is eroded metamorphic rocks change into igneous rock

Solid tin exists in two forms: white and gray. for the transformation sn(s, white) → sn(s, gray) the enthalpy change is -2.1 kj/mol and the entropy change is -7.4 j/(mol*k). a. calculate the gibbs free energy change for the conversion of 1.00 mol white tin to gray tin at -30℃. b. will white tin convert spontaneously to gray tin at -30℃? c. at what temperature are white and gray tin thermodynamically equivalent at a pressure of 1 atm?