Given that g for the reaction below is –957.9 kj, what is gf of h2o? 4nh3(g) + 5o2(g) =4no(g) + 6h2o(g)

gf,

nh3 = -16.66 kj/mol

gf, no = 86.71 kj/mol –228.6 kj/mol –206.4 kj/mol 46.7 kj/mol 90.7 kj/mol

- 228.6 kJ/mol.

Explanation:

∵ ΔGrxn = ∑ΔGf, products - ∑ΔGf, reactants

4NH₃(g) + 5O₂(g) → 4NO(g) + 6H₂O,  

∴ ΔGrxn = [6(ΔGf, H₂O) + 4(ΔGf, NO)] - [4(ΔGf, NH₃) + 5(ΔGf, O₂)]

ΔGrxn = – 957.9 kJ, ΔGf, H₂O = ??? KJ/mol, ΔGf, NO = 86.71 kJ/mol, ΔGf, NH₃ = - 16.66 kJ/mol, ΔGf, O₂ = 0.0 kJ/mol.

∴ – 957.9 kJ = [6(ΔGf, H₂O) + 4(86.71 kJ/mol)] - [4(- 16.66 kJ/mol) + 5(0.0 kJ/mol)].

– 957.9 kJ = 6(ΔGf, H₂O) + 346.8 kJ/mol + 66.64 kJ/mol

– 957.9 kJ = 6(ΔGf, H₂O) + 413.8 kJ/mol

6(ΔGf, H₂O) = – 957.9 kJ - 413.8 kJ/mol = - 1372 kJ/mol.

∴ ΔGf, H₂O = (- 1372 kJ/mol)/6 = - 228.6 kJ/mol.

radioactive decay occurs in unstable atomic nuclei – that is, ones that don't have enough binding energy to hold

the nucleus together due to an excess of either protons or neutrons.

definition

                    entropy is a measure of the randomness or the extent of disorder of a chemical process.

                      enthalpy is a measure of the heat change of a reaction occurring at a constant pressure.

measurement units:

                        entropy is measured in joule per kelvin (jk⁻¹)   whereas enthalpy is measured in joule per mole (jmol⁻¹)

requirements:

                            entropy has no requirements or limits, and its change is measured by the division between the heat change of the chemical process and the temperature.

                              in contrast, enthalpy can only be related to the heat change of the reaction under standard conditions.