"the orientation in space of an orbital is designated" by which quantum number

m. The magnetic quantum number m determines the orientation of an orbital in space.

For example, a p orbital has the allowed quantum numbers m = -1, 0, 1.

We customarily assign these numbers to the px, py, and pz orbitals pointing along the x-, y-, and z-axes.

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.