If the carbothermic reduction of SiO2 occurs at around 2,000°C and has a reaction enthalpy of around 1,100kJ/mol Si (12kWh/kg Si) produced, how does the magnesiothermic reduction of SiO2 occur at only 650°C when the reaction enthalpy is around 2,100kJ/mol Si (21kWh/kg Si) produced?