问题 问答题

为测定某石灰石样品中CaCO3的质量分数,取该样品6.0g,装入烧杯中,加入36.5g稀盐酸,恰好完全反应(样品中的杂质不溶于水且不与盐酸反应).反应后过滤,得不饱和CaCl2溶液39.3g.(假设操作过程中溶液无损失)

试计算:①样品中CaCO3的质量分数. ②稀盐酸中溶质的质量分数.

答案

(1)设样品中CaCO3质量为x

CaCO3+2HCl=CaCl2+CO2↑+H2O

100    73        44

x     

73x 
100
    
44x 
100

依题意:x+36.5g=39.3g+

44x 
100
,x=5.0g

CaCO3的质量分数:

5.0g
6.0g
×100%=83%

(2)稀盐酸中溶质的质量分数:

73×5.0g/100
36.5g
×100%=10%

答:样品中CaCO3的质量分数为83%;稀盐酸中溶质的质量分数是10%.

故答案为:①83%;②10%.

单项选择题

Regardless of their political affiliation, in all countries women must overcome a host of stumbling blocks that limit their political careers. "Most obstacles to progress consist of (1) of various kinds," says the Inter-Parliamentary Union (IPU), a Geneva-based organization (2) 139 parliaments, including the lack of time, training, information, self-confidence, money, support, motivation, women’s networks and solidarity between women.

In every culture, prejudice and stereotypes (3) hard. The belief still holds (4) that women belong in the kitchen and (5) the children, not at election (6) or in the Speaker’s chair. The media often reinforce traditional images of women, who, upon entering politics, also bear the brunt (正面冲击) of verbal and physical (7) .

In impoverished (贫穷的) countries (8) by civil conflicts and deteriorating economic and social conditions, women are (9) by the tasks of managing everyday life and looking after their families.

The IPU stresses the general lack of child-care facilities—often (10) a privileged few—the (11) of political parties to change the times and running of meetings and the weak backing women receive from their families. That support, which is (12) as well as financial, is (13) vital because women have internalized (14) images of themselves since the (15) of time and often suffer from low self-confidence.

Another obstacle is the lack of financial resources, especially as election campaigns become increasingly expensive. (16) , women encounter more or less open machismo (男子汉的高傲) in the (17) of closed political circles (18) entry to the "second sex. " Lastly, they (19) the lack of solidarity between women, (20) by the fact that the number of available positions is limited.

13()

A. all the same

B. at most

C. all the more

D. above all

单项选择题