题干

现有甲、乙、丙三名同学分别进行Fe(OH)3胶体的制备实验.甲同学向1mol•L﹣1氯化铁溶液中加入少量的NaOH溶液;

乙同学直接加热煮沸饱和FeCl3溶液;

丙同学向25ml沸水中逐滴加入1~2mL FeCl3饱和溶液,继续煮沸至液体呈红褐色,停止加热.

试回答下列问题:

上一题 下一题 0.0难度 选择题 更新时间:2013-06-14 10:36:11

答案(点此获取答案解析)

同类题2

阅读理解

    If you're ever apart from your children, a new study says just talking on the phone will help just as much as a hug (拥抱).

    If you're a parent who spends long hours on the job, you probably feel sorry for spending so much time away from your kids. But the results of a new study show that a mother's voice alone can be just as comforting to an anxious child as physical contact (接触).

    In an experiment, researchers from the University of Wisconsin Madison asked a group of girls between the ages of 7 and 12 to solve math problems in front of judges — a stressful situation for anyone. Before the girls were set to give their answers, the researchers measured their levels of two hormones(荷尔蒙):cortisol,which goes up during stressful periods, and oxytocin, the “love” hormone, which goes down at the same time.

    After the girls finished the problems, some of them got to meet up with their mothers right away. The moms came in and hugged the girls. Another group of the girls didn't see their mothers, but received phone calls from them, in which their mothers told them how well they'd done. The final group had no contact with their mothers, but instead watched an animal movie, March of the Penguins.

    Finally, the girls' hormone levels were measured again. Although the movie was interesting, it did nothing to reduce the children's anxiety—but, surprisingly, both the physical contact and phone calls from their mothers had the same effect on reducing the girls' stress levels.

    So, no matter how old you are, if you're feeling stressed about something in your life, a phone call to Mom might be just the key to help you feel better.