不同粒径纳米氧化镁的标准摩尔生成焓的测定

Determination of Standard Molar Enthalpies of Formation of Nano-MgO Systems with Different Particle Sizes

通过对6种不同粒径的纳米氧化镁进行表征,确定了其形貌和粒径大小。根据盖斯定律设计热循环,用溶解热法测定并计算得到不同粒径的纳米氧化镁的标准摩尔生成焓分别为:Δ_fH_m~θ(MgO,100nm)=-(726.01±0.04)kJ/mol;Δ_fH_m~θ(MgO,90nm)=-(729.63±0.04)kJ/mol;Δ_fH_m~θ(MgO,70nm)=-(738.41±0.04)kJ/mol;Δ_fH_m~θ(MgO,60nm)=-(742.39±0.04)kJ/mol;Δ_fH_m~θ(MgO,40nm)=-(747.68±0.04)kJ/mol;Δ_fH_m~θ(MgO,20nm)=-(754.93±0.04)kJ/mol。结果表明,随着纳米氧化镁粒径的减小,标准摩尔生成焓减小,并满足二次函数关系:Δ_fH_m~θ/kJ·kmol^(-1)=-759.846+0.242(r/nm)+0.001(r/nm)~2。

Sixnano-MgO samples were characterized, and the morphologies and pariticle sizes were determined. To obtain the standard molar enthalpies of formation （AsH~） of nano-MgO systems with different particle sizes, according to the law of Hess, the dissolution heat of the designed thermochemical cycle was measured, and the enthalpy results were listed as follows： Δ_fH_m~θ（MgO,100nm）=-（726.01±0.04）kJ/mol;Δ_fH_m~θ（MgO,90nm）=-（729.63±0.04）kJ/mol;Δ_fH_m~θ（MgO,70nm）=-（738.41±0.04）kJ/mol;Δ_fH_m~θ（MgO,60nm）=-（742.39±0.04）kJ/mol;Δ_fH_m~θ（MgO,40nm）=-（747.68±0.04）kJ/mol;Δ_fH_m~θ（MgO,20nm）=-（754.93±0.04）kJ/mol-1. The results show thatthe standard molar enthalpy of formation of nano-MgO systems decreases with the particle size, and the relation between Δ_fH and particle size r was de- termined to be Δ_fH_m~θ/kJ·kmol^（-1）=-759.846＋0.242（r/nm）＋0.001（r/nm）2.