题干

对于某些离子的检验及结论一定正确的是(   )

A:加入稀盐酸产生无色气体,将气体通入澄清石灰水中,溶液变浑浊,一定有CO32

B:加入氯化钡溶液有白色沉淀产生,再加盐酸,沉淀不消失,一定有SO42

C:加入硝酸酸化的硝酸钡溶液既无沉淀也无气体生成,再加硝酸银溶液立即出现白色沉淀,一定有Cl

D:加入碳酸钠溶液产生白色沉淀,再加盐酸白色沉淀消失,一定有Ca2+

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答案(点此获取答案解析)

C

同类题1

阅读下面短文,掌握其大意,然后从各题所给的A、B、C和D项中,选出最佳选项。

    When I first entered university, my aunt, who is an English professor, gave me a new English dictionary. I was 1to see that it was an English dictionary, also known as a monolingual dictionary.2it was a dictionary intended for non—native learners, none of my classmates had one, 3, to be honest, I found it extremely 4 to use at first. I would look up words in the dictionary and 5 not fully understand the meaning. I was used to the 6 bilingual dictionaries, in which the words are 7 both in English and Chinese. I really wondered why my aunt 8 to make things so difficult for me. Now, after studying English at university for three years, I 9 that monolingual dictionaries are 10 in learning a foreign language As I found out, there is 11 often no perfect equivalence(对应)between two 12 in two language. My aunt even goes so far as to 13 that a Chinese "equivalent" can never give you the 14 meaning of a word in English! 15, she insisted that I read the definition(定 义) of a world in a monolingual dictionary 16 I wanted to get a better understanding of its meaning. 17, I have come to see what she meant. Using a monolingual dictionary for learners has helped me in another important way. This dictionary uses a(n) 18 number of words, around 2, 000, in its definitions. When I read these definitions, I am 19 exposed to(接触)the basic words and learn how they are used to explain objects and ideas. 20 this, I can express myself more easily in English.