For the reduction reaction $$2no(g)+2h2(g) n2(g)+2h2o(g) which occurs at high temperatures, the experimentally determined rate law is: rate = k[no]2[h2] here is a proposed mechanism for the reduction of no by h2: elementary step 1: $$h2(g)+no(g) n(g)+h2o(g) elementary step 2: $$n(g)+no(g) n2(g)+o(g) elementary step 3: $$h2(g)+o(g) h2o(g)

a compound is a molecule made of atoms from different elements.

a. by the combination of an unlimited number of elements

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.