欲测定某天然水样的BOD5含量，取100mL水样，以淀粉为指示剂，以0.02mol/L的？

BOD5=DO培养前-DO培养后 DO培养前=(v1-v2)*0.0125*8*1000/V=(7-4)*0.0125*8*1000/100=3mg/L DO培养后=(3-0.2)*0.0125*8*1000/100=2.8mg/L f1=29/30=0.966 f2=1/30=0.033 BOD5=(3-2.8)*0.966/0.033=5.8mg/L

【】p(CaCO3mg/L) = (V1/V2)1000.9 = (2.41ml/100.0ml)1000.9 = 24.1 【】p(CaCO3mmol/L) = p(CaCO3mg/L) 0.02= 24.1 x0.02 = 0.482

EDTA和钙离子及镁离子都生成1 :1的配合物 钙离子含量=0.01000*16.48*40.08/(100/1000)=66.05mg/L 镁离子含量=0.01000*(22.66-16.48)*34.31/(100/1000)=15.02mgL

消耗的EDTA的摩尔数为0.02*/103*30=6*10-3根据水的硬度定义来计算(以CaO计).CaO的质量为6*10-3*56=3.36*10-1g所以水的硬度为3.36*10-1/130*10-3=260g/L=2.60*105 mg/L