搜题请搜索小程序“爱下问搜题”
问题 填空题

请用化学方程式表示下列反应原理。

（1）鉴别稀盐酸和稀硫酸。

（2）生石灰用作食品包装袋内的干燥剂。

（3）工业上用碳酸钠溶液和石灰水制取烧碱

答案

（1）BaCl2 + H2SO4=BaSO4↓+ 2HCl（2）CaO + H2O=Ca(OH)2（3）Na2CO3 + Ca (OH)2=CaCO3↓+ 2NaOH

题目分析：（1）鉴别稀盐酸和稀硫酸。其原理为：BaCl2 + H2SO4=BaSO4↓+ 2HCl；（2）生石灰用作食品包装袋内的干燥剂原理为：CaO + H2O=Ca(OH)2；（3）工业上用碳酸钠溶液和石灰水制取烧碱原理为Na2CO3 + Ca (OH)2=CaCO3↓+ 2NaOH

填空题

How did the Olympic Games start In ancient Greece athletic festivals were very important and had p ________ (1). Originally the Festival was held in honour of .Zeus, the supreme god in Greek Mythology. Eventually the Olympian athletic festival had lost its ________ (2) and became an international event. No one knows exactly ________ (3) the Olympic Games go, but some scholars recorded date from 776 B.C.According to some scholars, at first the only Olympic event was ________ (4), called a stadium and that was the only event until 724 B.C. After that, other ________ (5) were added and sixteen years later in ________ (6) the pentathlon was added and wrestling became part of the games. This pentathlon was a five-event match which ________ (7) running, wrestling, leaping, throwing the discus, and hurling the javelin.The games were held ________ (8) and after an uninterrupted history of 1170 years, the games ________ (9) in A.D. 394, the Christian era, because of their pagan origin.It was over ________ (10) before there was another such international athletics gathering. In 1896, the first of the modern ________ (11) opened in Athens, Greece.Nowadays, the Games are held in different countries ________ (12). The host country provides vast facilities such as stadiums and ________ (13).Many more sports are represented, including the very celebrated event: ________ (14).The Olympics start with the arrival in the stadium of a torch, ________ (15) on Mount Olympus by the sun’s rays. The torch is carried by ________ (16) to the stadium. The Olympic flame symbolizes the ________ (17) of the ancient Greek athletic ideals, and it burns throughout the Games until ________ (18). The well-known Olympic flag, however, is ________ (19): the five interlocking rings symbolize the uniting of all five continents ________ (20).
查看答案
填空题

轴流泵中有（）和推力轴承两种。
查看答案