某厂排放的废水中含有碳酸钠，易造成环境污染。化学兴趣小组为该厂设计废水处理和利用的方案，进行了如下实验：取过滤后的水样200 g，逐滴加入稀盐酸至恰好不再产生气体为止，反应过程中生成气体与所加稀盐酸的质量关系如图所示。请回答下列问题(不考虑水样中杂质的影响)：
(1)反应生产CO2气体的质量是____g;
(2)反应后生成氯化钠的质量是多少?(请写出计算过程)
(3)农业上常用10%～20%的氯化钠溶液来选种。请通过列式计算判断：上述实验反应后所得溶液能否直接用于农业上选种?
(1)反应生产CO2气体的质量是4.4g;
(2)解：设反应后生成氯化钠的质量为x。
Na2CO3+2HCl===2NaCl+H2O+CO2↑
117 44
x 4.4 g
11744=x4.4 g x=117×4.4 g44=11.7 g
(3)反应后溶液中溶质的质量分数为：
11.7 g200 g+38.4 g-4.4 g×100%=5%<10%，故不能直接用于农业上选种。
Dogs are the best pets of humans. They come in all sizes. Some dogs are as small as a football, and others are as tall as a desk. Dogs’ fur (毛) is different, too. It can be long and soft, or smooth and hard. People don’t mind the kind of fur, because all dogs are good to hug.
请在字典中查一下这个词。
我喜欢甜食， 你知道的。
去年， 彼得在旅途中和许多人交了朋友。
我叫托尼· 史密斯， 史密斯是我的姓。
我们在课上回答问题时应该起立
Tea and coffee are two of the most popular drinks in the world. However, people usually like one more than the other. These drinks also have very different uses.
People in the office usually sit for most of the day when they work. But this is bad for a person’s health. When people sit for too long every day, they don’t move very much. So it is easy to start getting fat. Sitting too long is also bad for their work because it makes them want to sleep. When this happens, people may make more mistakes in their work or spend more time finishing their work. Companies need workers to be healthy, so how do they fix the problem?
