题干

某同学从定量角度研究双氧水制取氧气的过程,对原实验进行部分改进,增加了称量操作.具体做法是:取10%的双氧水和少量的二氧化锰放入气体发生装置,并对反应前后混合物的质量进行称量,记录如下:

若反应后,双氧水分解完全且氧气全部逸出,该同学得出的结论中,不合理的是()

A:反应速率逐渐加快

B:最多得到氧气的质量为1.6g

C:催化剂二氧化锰的质量为0.3g

D:反应得到水和氧气的质量比为9:8

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答案(点此获取答案解析)

A

同类题5

阅读短文,从每题所给的四个选项(A、B、C和D)中,选出最佳选项。

    Many kids don't drink enough water daily, according to a new study. The study's lead author, Erica Kenney, at first planned to look into the amount of sugary drinks kids were drinking in schools. However, during her research she found that many kids were simply not drinking enough water.

    Kenney and her team examined data from a group of 4,000 children, aged 6 to19. The data was taken from the National Health and Nutrition Survey, a study on the health of children in the United States done each year by the Center for Disease Control and Prevention.

    While looking through the survey results, she noticed that more than half of the kids who took part in the study were dehydrated (脱水的). Of that group, boys were 76% more likely than girls not to have enough water in their system. Nearly one quarter of the kids in the survey reported drinking no plain water at all.

    “These findings highlight (突出) a possible health issue that wasn't given a lot of attention in the past,” Kenney said in a statement. “Even though for most of these kids this is not an immediate and great health risk, this is an issue that could really be reducing quality of life and well-being for many children and youth.”

    The United States-National Agriculture Library says average kids need between 10 to 14 cups of water every day. This water can come from a mix of drinks and foods that contain high amounts of water, such as celery, melons or tomatoes. It is also suggested that fluids (液体) come from water instead of sugary drinks that are high in calories and can lead to weight problems.