Hi, i am a 3rd year in General Chemistry, freshmen at a university, and i have a few problems that i've encountered along the way. These questions has been bugging me for a long time now and i really hope someone can fill in the holes and gaps in for me..anyways here they are 1) Lets say you have a .00035 L volume of .25 M Pb(NO2). What are the moles of Pb2+? This is my guess on how to do this. Since molarity = moles/volume...molarity of pb2+ = moles of pb2+/.00035 But how would i know what the molarity of Pb2+ is?? Can i just use .25 M Pb(N02) instead? Is it the same thing or am i missing something here 2) Lets say you put a test tube which has a solid in a hot bath for 30 seconds. Then you shake and stir the test tube and the solid precipitates. Is this an endo or exo thermic reaction? My guess is that its exo, because the surroundings are hot? But i am not sure, since the precipitate dissapears, wouldnt the equilibrium shift to the reactant side, meaning few products, which means endothermic?? 3) Lets say you have a pH of 0.10 M HCN solution which is 5.2. What is the [H+] and [CN-]. I know that pH = -log[H+], so to find the [H+] i would just take the antilog, but then how would i find the [CN-]?