问题 选择题

为了配制NH4+浓度与Cl-的浓度比为1:1的溶液,可在NH4Cl溶液中加入①适量的HCl②适量的NaCl③适量的氨水④适量的NaOH,正确的是( )

A.①②

B.③

C.③④

D.④

答案

答案:B

题目分析:在溶液中NH4Cl=NH4++Cl-. 由于发生水解反应:NH4++ H2ONH3·H2O+ H。所以c(Cl)>c(NH4+)。为了使溶液中NH4+浓度与Cl-的浓度比为1:1,应该加入物质来抑制该水解反应的进行。①适量的HCl,平衡逆向移动,c(NH4+)增大,都是c(Cl)也增大,所以仍然是c(Cl)>c(NH4+)。错误。②适量的NaCl,由于溶液的稀释作用,NH4+水解程度增大,c(NH4+)减小,c(Cl)增大,所以仍然是c(Cl)>c(NH4+)。错误。③适量的氨水NH3·H2O电离产生NH4+,使c(NH4+)增大,Cl则由于氨水的稀释作用c(Cl)减小。因此可以形成NH4+浓度与Cl-的浓度比为1:1的溶液。正确。④适量的NaOH,OH-会消耗H,使NH4+水解程度增大,c(NH4+)进一步减小,NH4+浓度与Cl-的浓度比比1:1更小。错误。

阅读理解

How do you feel when you stay in hospital alone? Jenny, 13, a US student, feels bored. She knows the feeling because she has been in hospital many times herself. One day, she thought of an idea—if patients could get some books to read, they would feel better. So, from May, she and many of her friends began to collect books for hospital patients.

In six months the students collected 1,250 books at school. They decided to donate the books to the North Shore Medical Centre, a children’s hospital next door to their school. “There are books for kids of all ages, from babies up to high school level.” said Jenny.

The students put the books into “early readers”, “middle readers” and “advanced readers”. Then they wrote their best wishes to patients on bookmarks (书签) and letters, put the books in big boxes and donated them to the hospital.

“We wrote things like, “Keep on reading!’ and ‘Hope you feel better!’,” siad John, 14, Jenny’s brother. “And we also wrote some funny things to make them laugh.”

Frank, 12, and Steven, 14, helped carry 16 large boxes of books into a car. “I think these books will make me a lot of patients feel happy.” said Frank. Steven shared his opinion. “It is really the most meaningful thing that I have ever done in my life.”

小题1:Who first thought of the idea of helping those bored patients in hospital?

A.John.

B.Frank.

C.Steven.

D.Jenny.小题2:From the article, we can learn that _______.

A.in half a year Jenny and her friends bought 1,250 books

B.the North Shore Medical Centre is far from Jenny’s school

C.Jenny and her friends were willing to help bored patients

D.Steven had a different opinion from Frank and John小题3:The best title for the article might be “_______”.

A.Collecting books for bored patients

B.Writing a letter to a medical centre

C.Donating books to poor students

D.Reading books for hospital patients小题4: Which of the following words can be used to describe those student?

A.Polite and hard-working

B.Lazy and stubborn

C.Selfish and proud

D.Thoughtful and helpful

多项选择题