How to tell if a reaction is endothermic or exothermic?

Which class of molecules functions as chemical signals? hormones water carbohydrates proteins

A5.000 g sample of niso4 h2o decomposed to give 2.755 g of anhydrous niso4. what is the formula of the hydrate? what is the full chemical name for the hydrate? what is the molar mass of the hydrate? niso4•_h2o what is the mass % of water in the hydrate?

Which electron configuration represents the electrons in an atom of sodium in the ground state at stp