The stereoselectivity of the wittig reaction is due in part to the choice of base and steric effects. true or false

lithosphere and asthenosphere

56 moles of   lieter in chemistry

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

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.