17.(9分,除标注外,每空2分)(1)dgf(共2分)(3)Ca2+hco、nhcl4)B18.(13分,除标注外,每空2分)(1)防止PbCl结晶析出SiO2和Fe(OH(2)盐酸(1分) (4)+20H ---PbO+H:O(5)pb++2h2-2e-pbO2+4H9.6