Given the standard enthalpy changes for the following two reactions: (1) 2Pb(s) + O2(g)2PbO(s). ΔH° = -434.6 kJ

(2) 2Zn(s) + O2(g)2ZnO(s).ΔH° = -696.6 kJ

what is the standard enthalpy change for the reaction:

(3) PbO(s) + Zn(s)Pb(s) + ZnO(s).ΔH° = __kJ

What is the number of moles in 15.0 g ash3?

6. using 3 – 4 sentences explain (in your own words) why water expands when it freezes? 7. using your knowledge of colligative properties explain whether sodium chloride or calcium chloride would be a more effective substance to melt the ice on a slick sidewalk. use 3 – 4 sentences in your explanation.

Imagine that you push on a large rock. at what point does your effort change the rock’s mechanical energy?