问题 计算题

某化学兴趣小组为测定某大理石样品中碳酸钙的含量,将适量的稀盐酸加入到20g大理石中(其它成分不与盐酸反应),再将产生的CO2气体用足量的澄清石灰水吸收,同时测量2分钟内石灰水增加的质量,结果如下表所示:

(1) * * 生二氧化碳气体__________g。

(2)计算大理石样品中碳酸钙的质量分数(写出计算过程)。

答案

(1)6.6

(2)解:设样品中碳酸钙的质量为x

CaCO3+2HCl==CaCl2+H2O+CO2

100            44

x             6.6g

100:44= x:6.6g

x=15g

样品中碳酸钙的质量分数=15g/20g ×100% = 75%

阅读理解

阅读理解

     Compared to adults, children seem to be moving constantly.So it’s no surprise that most parents who

are quizzed about their child’s physical activity level describe their children as fairly active.But a new study of nearly 2,000 British school children suggests that many parents overestimate the amount of physical

activity their children are really getting.

     The researchers equipped 1,892 British school children, ages 9 and 10, with accelerometers that

measure all physical activity during a given time period.The research, known as the Speedy study

collected the exercise data from children at 92 schools in Norfolk, England, between April and July 2007.

     A child was regarded inactive if he or she recorded less than an hour a day of physical activity.

Although the majority of children studied were getting enough physical activity, a_sizable_minority_of_

children_were_not.Overall,39 percent of girls and 18 percent of boys studied were getting less than an

hour of physical activity each day.

     But if you asked the parents of the inactive children to describe their child’s activity level, the vast

majority-80 percent-described their children as fairly or very physically active, according to the findings

published in the American Journal of Preventive Medicine.Interestingly, the children themselves had

more awareness about their lack of physical activity.Overall,40 percent of children overestimated their

physical activity.

     But it wasn’t the parents of overweight children who were most likely to guess wrong about physical

activity levels.The parents who were most out of touch about their child’s physical fitness were more

likely to have children who were slim.Parents of girls were also more likely to overestimate physical

activity.The researchers noted that parents should be educated about the importance of physical activity

for children even if the child is not overweight.

    “Parents of slim children appear to assume that their children are adequately  active, ”  the study

authors reported.“Increasing awareness regarding health benefits of physical activity beyond weight

control might help have a correct idea of physical activity levels and encourage behavior change.”

1. According to the Speedy study, what kind of children can be judged physically inactive?

A. Slim children.

B. Children with less than an hour a day of physical activity.

C. Overweight children.

D. Children out of touch with their parents for a long time.

2. What does the writer probably mean by saying “a sizable minority of children were not” in Paragraph 3?

A. The amount of children’s physical activity is far from the writer’s satisfaction.

B. Only a small number of children were not getting enough physical activity.

C. A small number of children didn’t overestimate their physical activity.

D. The minority of children were not studied at all.

3. The passage is intended to________.

A. encourage parents to fairly judge their children’s physical activity levels

B. persuade parents to keep an eye on their children’s weight

C. urge children to wear accelerometers during exercise

D. advise parents to keep in touch with their children

问答题 简答题