题型:问答题 简答题 (4分)已知Na2SO3易被空气氧化变质,欲用氧化还原滴定法来测定实验室里Na2SO3的纯度。取实验室里Na2SO3样品63g,溶于水配成250mL溶液。从其中取出25mL Na2SO3溶液用0.4mol·L-1酸性KMnO4溶液滴定,当溶液刚好变为紫色且半分钟不褪色时,用去40mL酸性KMnO4溶液(已知:5SO32-+2MnO4-+6H+ 5SO42-+2Mn2++3H2O)。则实验室里的Na2SO3的纯度为多少? 查看答案
题型:问答题 简答题 —Can you go to the concert with us? —Sorry, I can't. I have _____ homework.[ ]A. too much B. much too C. too many 查看答案