问题 选择题

一定温度下,在一容积不变的密闭容器中发生的可逆反应2X(g)  Y(g)+Z (s),以下能说明作为反应达到平衡标志的是 (  )

A.X的分解速率与Y的消耗速率相等

B.X、Y与Z的物质的量之比为2:1:1

C.混合气体的密度不再变化

D.单位时间内生成lmolY的同时分解2mol X

答案

答案:C

在一定条件下,当可逆反应中正反应速率和逆反应速率相等时(但不为0),各种物质的浓度或含量均不再发生变化的状态,是化学平衡状态。平衡时浓度不再发生变化,但物质之间的浓度不一定相等或满足某种关系,所以B不正确。A中反应速率的方向相反,但不满足速率之比是相应的化学计量数之比,A不正确。混合气的密度是混合气的质量和容器容积的比值,容积不变,但混合气的质量是变化的,C可以说明。D反应速率的方向是相同的,不能说明。答案选C。

单项选择题 A1/A2型题
阅读理解

阅温度理解。

     A Father’s day is a day set aside for honouring fathers in church services and in the home. It’s

celebrated in the U.S. in the third Sunday of June. This idea was begun by Mrs John Bruces Dodd,

who in 1909 persuaded an organization in Washington to

     salute fathers with special church services. The idea was officially agreed to by President Woodrow

Wilson in 1916. In 1924, President Calvin Coolidge suggested national celebration of the day to

form closer relations between fathers and their children, and to impress upon fathers the full measure

of their duties. The red or white rose is recognized as the official Father’s Day flower.

1. Father’s Day, at first, meant ______.

A. to honor fathers in church services and in the home

B. to win honor for fathers in church services

C. to do honour to fathers at home

D. to warn the fathers of their duties

2. Father’s Day was first celebrated by _____.

A. the French      

B. the British      

C. the German      

D. the American

3. The first president who agreed to Father’s Day was _____.

A. Woodrow Wilson

B. Calvin Coolidge

C. George Washington

D. Abraham Lincoln

4. The president wanted Father’s Day to be a day on which _____.

A. people remembered their fathers

B. the relations between fathers and their children became closer

C. fathers must remember that they should be good fathers

D. both B and C

5. According to the passage, this idea was begun by______.

A. Woodrow Wilson    

B. Calvin Coolidge

C. George Washington    

D. Mrs. John Bruces Dodd