问题 选择题

下列叙述正确的是(  )

A.用pH=2和pH=3的醋酸溶液中和含等量NaOH的溶液所消耗的醋酸溶液的体积分别为Va和Vb,则Va=10Vb

B.pH相等的NaOH、CH3COONa和NaHCO3三种溶液,则有:c(NaOH)<c(CH3COONa)<c(NaHCO3

C.过量SO2通入到Ba(NO32溶液中,正确的离子反应方程式为:3SO2+2NO3-+3Ba2++2H2O═3BaSO4↓+2NO↑+4H+

D.向Ca(HCO32溶液加少量氢氧化钠溶液:Ca2++2HCO3-+2OH-═CaCO3↓+CO32-+2H2O

答案

A、含等物质的量NaOH的溶液分别用pH为2和3的CH3COOH溶液中和,则有二者物质的量相等,因为所中和的氢氧化钠的物质的量是一定的,而醋酸是弱酸,醋酸为弱电解质,浓度越大,电离程度越小,pH为2和3的CH3COOH溶液,后者电离程度大,pH为2的CH3COOH的浓度大于pH为3的CH3COOH溶液的浓度的10倍,

设pH为2的醋酸浓度为x,PH=3的醋酸浓度为y,则有Va×x=Vb×y,则

Va
Vb
=
y
x
1
10
,即Vb>10Va,故A错误;

B、氢氧化钠是强碱,不水解,相同浓度的三种溶液氢氧化钠的pH最大,所以pH相同的三种溶液中,氢氧化钠浓度最低,已知酸性:CH3COOH>H2CO3>HCO3-,所以碳酸氢钠的水解程度大于醋酸钠,则醋酸钠的浓度大于碳酸氢钠,碳酸氢钠的浓度大于氢氧化钠,则c(NaOH)<c(NaHCO3)<c(CH3COONa),故B错误;

C、少量SO2通入Ba(NO32溶液,反应的离子方程式为:3SO2+2NO3-+3Ba2++2H2O═3BaSO4↓+2NO↑+4H+,离子方程式书写正确,故C正确;

D、向Ca(HCO32溶液加少量氢氧化钠溶液,少量的氢氧根离子为1mol,反应的离子方程式为:Ca2++HCO3-+OH-═CaCO3+H2O,故D错误;

故选C.

单项选择题 A1/A2型题
阅读理解

About 21,000 young people in 17 American States don’t attend classes in school buildings. Instead, they receive their elementary (初等) and high school education by working at home on computers . The Center for Education Reform says the United States has 67 public “cyberschools,” and that is about twice as many as two years ago.

The money for students to attend a cyberschool comes from the governments of the states where they live. Some educators say cyberschools receive money that should support traditional public schools . They also say it is difficult to know if students are learning well.

Other educators praise this new form of education for letting students work at their own speed. These people say cyberschools help students who were unhappy or unsuccessful in traditional schools . They say learning at home by computers ends long bus rides for children who live far from school.

Whatever the judgment of cyberschools , they are getting more and more popular.

For example , a new cyberschool called Commonwealth Connections Academy will take in students this fall. It will serve children in the state of Pennsylvania from ages five through thirteen.

Children get free equipment for their online education. This includes a computer, a printer, books and technical services. Parents and students talk with teachers by telephones or by sending emails through their computers when necessary.

Students at cyberschools usually do not know one another. But 56 such students who finished studies at Western Pennsylvania Cyber Charter school recently met for the first time. They were guests of honor at their graduation.

小题1:What do we know from the text about students of a cyberschool?

A.They have to take long bus rides to school.

B.They study at home rather than in classrooms.

C.They receive money from traditional public schools.

D.They do well in traditional school programs.小题2:What is a problem with cyberschools?

A.Their equipment costs a lot of money.

B.They get little support from the state government

C.It is hard to know students’ progress in learning.

D.The students find it hard to make friends.小题3: Cyberschools are getting popular because    

A.they are less expensive for students

B.their students can work at their own speed

C.their graduates are more successful in society

D.they serve students in a wider age range小题4:We can infer that the author of the text is _________.

A.unprejudiced(无偏见的) in his description of cryberschools .

B.excited about the future of cryberschools

C.doubtful about the quality of cryberschools

D.disappointed at the development of cryberschools.