目前家中常用的洗涤剂中有一种三聚磷酸钠(Na5P3O10)的物质,它是污水中磷元素的主要来源,常引起水中富营养化问题。Na5P3O10中磷元素的化合价为:
---I use your ruler, Lingling? --- Sure. Here you are.
--- Do you like watching TV? ---Yes, I. But only after I finish my homework.
Li Yan is my best friend. She comes a small village.
How is your father? Please say hello to ______ for me.
下列关于实验室制氧气并用排水法收集的实验操作先后顺序中不正确的是()