问题
单项选择题
最适宜于开挖含水量不超过27%的松土和普通土的土方施工机械为()。
A.铲运机
B.正铲挖土机
C.反铲挖土机
D.抓铲挖土机
答案
参考答案:A
最适宜于开挖含水量不超过27%的松土和普通土的土方施工机械为()。
A.铲运机
B.正铲挖土机
C.反铲挖土机
D.抓铲挖土机
参考答案:A
完形填空。 | ||||
Ben is ① some plans ② his summer holiday. ③ July, he wants to finish his homework and he would like ④ some housework at home. Sometimes, he ⑤ for his parents. In August, he ⑥ the Internet and play computer games ⑦ Sundays. He will go on an outing with his friends every Saturday morning. But the most important day is the 19th of October. ⑧ that day, he is going to ⑨ a singing contest with Nancy, Lucy, David and Tom at the Sun Theatre. During the last ten days of the holiday, he is going to ⑩ movie with his parents. Then, he must prepare for the new term.
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化学兴趣小组对某石灰石样品中碳酸钙的含量进行实验探究.该小组取用4g样品,测定该石灰石的纯度,用未知溶质质量分数的稀盐酸40g分4次加入.每次充分反应后,经过滤、干燥等操作后称量固体的质量.(假设过滤、干燥等操作过程,固体物质的质量不受损耗;石灰石中的杂质不与盐酸反应,也不溶于水.)实验结果见下表:
稀盐酸的用量 | 第一次加入10g | 第二次加入10g | 第三次加入10g | 第四次加入10g |
剩余固体的质量 | 3.0g | 2.0g | 1.0g | 0.4g |
(2)所用的稀盐酸中,溶质的质量分数是多少?
(3)4g石灰石样品与足量的稀盐酸反应,生成二氧化碳多少克?