硫代硫酸钠C(1/2NaS2O3)与硫代硫酸钠C(Na2S2O3)有啥区别这两种写法有什么意义?0.1N硫代硫酸钠C(1/2NaS2O3)=0.1mol/l,是称取25g0.1N硫代硫酸钠C(Na2S2O3)呢?