除去下列物质中的少量杂质（括号内为杂质）的方法错误的是（ ）
A．O2（H2O）﹣用生石灰
B．NaCl溶液（KNO3）﹣降温结晶
C．CaCO3粉末（Na2CO3）﹣加水过滤
D．KCl溶液（K2CO3）﹣加适量盐酸
答案：B
题目分析：根据主要物质和杂质的性质的不同来分析。
A、生石灰能与杂质水反应生成氢氧化钙，而主要物质氧气不能与生石灰反应，故用生石灰能除去杂质，正确；
B、硝酸钾的溶解度受温度的影响较大，氯化钠的溶解度受温度影响的较小，且由于硝酸钾在混合物中的含量较低，故降温结晶不能使氯化钠溶液与硝酸钾分离，错误；
C、杂质Na2CO3易溶于水，而主要物质CaCO3粉末难溶于水，故加水过滤能除去杂质，正确；
D、杂质K2CO3能与盐酸反应生成氯化钾、水和二氧化碳，而主要物质氯化钾与盐酸不反应，故加适量盐酸能除去杂质且没有引入新的杂质，正确。故选B
点评：一般的除杂质题必须同时满足两个条件：①加入的试剂只能与杂质反应，不能与原物质反应，②反应时不能加入新的杂质，这是正确解题的关键。
A man was bitterly envious of his neighbour．He spent long hours in prayer，wanting to be to his neighbour in every aspect of life． One night，God appeared before him in a dream and said，“I am pleased with your ．Ask for a gift． your neighbour will get the same gift in double amount．” He was glad but sad that his enemy would get a greater gift．He requested，“God， the sight in one of my eyes．” With his single eye，he peeped at his neighbour but was to see his neighbour's sight was not lost! Confused，he to God，“Why don’t you keep your word?” God said，“Son，I always keep my word． is not a gift，but a curse．You have the gift of sight in only one eye now，as asked by you．But your neighbour has sight in both of his eyes．I the gift．” He suddenly from his dream and was sure that it was a message from God．Englightened by the dream，he went to his neighbour and begged his pardon for thinking and acting him．They embraced each other and were good friends thereafter．
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