How many moles of H2O will be produced if 6.8 mol of O2 reacts completely with CH4

Can someone me with questions 12 and 13 plz.

Find the mass, in grams, of 5.00*10^23 molecules of f2

You are attempting to recrystallize a crude product mixture. you add the appropriate amount of hot solvent and are allowing the solution to slowly cool to room temperature. however, at room temperature no crystals have appeared, which of the following methods should be used to induce crystallization? choose all correct answers. a) place the flask in an ice bath. b) swirl the contents of the flask. c) add a small seed crystal of the desired product. d) scratch the inside of the glassware using a stir rod. it can be multiple choices