Consider the following reactions: 1)
H2(g) + % O2g ---> H20. H = -243 kJ/mol
2)
% N2(g) + % 028 + 90.7 kJ --->NO(R)
3)
C(s) + % 020) ---> CO2 + 111 kl
4)
% H2(g) + %128 ---> Hlo H = 26 kJ/mol
Which of the above reactions is exothermic?

every chemical equation adheres to the law of conservation of mass, which states that matter cannot be created or destroyed. therefore, there must be the same number of atoms of each element on each side of a chemical equation.

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.