题干

因为“1升水中大约能溶解1升二氧化碳”,所以我们常采用向上排空气集气法收集二氧化碳。在集满二氧化碳时,玻璃片的____ (填“毛”或“光”)面应朝下盖上集气瓶。有同学质疑:因为发生反应时排出气体的速度很快,二氧化碳与水接触的时间很短,溶解的量可能不大。于是他们决定探究二氧化碳是否能用排水集气法收集。他们查阅资料得到:①排水集气法收集时,二氧化碳在水中的溶解损失很小;②排空气集气法与排水集气法的二氧化碳纯度比较如表所示;他们得出的结论是:____

收集的方法

二氧化碳的纯度

排空气集气法

 71%

排水集气法

87.5%

上一题 下一题 0.0难度 选择题 更新时间:2019-09-19 05:13:08

答案(点此获取答案解析)

毛,二氧化碳能用排水法来收集

同类题1

阅读下列短文,从每题所给的A、B、C和D四个选项中,选出最佳选项。

C

    Teens and younger children are reading a lot less for fun, according to a Common Sense Media report published Monday.

    While the decline over the past decade is steep for teen readers, some data in the report shows that reading remains a big part of many children's lives, and indicates how parents might help encourage more reading.

    According to the report's key findings, "the proportion (比例) who say they 'hardly ever' read for fun has gone from 8 percent of 13-year-olds and 9 percent of 17-year-olds in 1984 to 22 percent and 27 percent respectively today."

    The report data shows that pleasure reading levels for younger children, ages2-8, remain largely the same. But the amount of time spent in reading each session has declined, from closer to an hour or more to closer to a half hour per session.

    When it comes to technology and reading, the report does little to counsel(建议)parenst looking for data about the effect of e-readers and tablets on reading. It does point out that many parents still limit electronic reading, mainly due to concerns about increased screen time.

    The most hopeful data shared in the report shows clear evidence of parents serving as examples and important guides for their kids when it comes to reading. Data shows that kids and teens who do read frequently, compared to infrequent readers, have more books in the home, more books purchased for them, parents who read more often, and parents who set aside time for them to read.

    As the end of school approaches, and school vacation reading lists loom(逼近)ahead, parents might take this chance to step in and make their own summer reading list and plan a family trip to the library or bookstore.