If a scuba tank filled with oxygen gas at 284k at 800 mmHg is heated to 400 k, what is the new pressure in mmHg

"hydrogen bonding is the attraction of h atoms in the water molecule (slight + charge) to o atoms in a neighboring water molecule (slight - charge); it is a weak interatomic force. but it is still strong enough to the water molecules "stick" together."

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.