搜题请搜索小程序“爱下问搜题”
问题 选择题

将固体NH4I置于密闭容器中，在某温度下，发生反应：

NH4I（气）NH3（气）＋HI（气），2HI（气）H2（气）＋I2（气）

当反应达到平衡时，c（H2）＝0.5mol/L，c（HI）= 4mol/L，则NH3的浓度为

A．3.5mol/L

B．4.5mol/L

C．4mol/L

D．5mol/L

答案

答案：D

题目分析：由氢气的浓度求算分解的碘化氢的浓度，c（HI）= 4mol/L，为剩余的HI浓度，进而求出第一个反应生成的HI：2HI（气）H2（气）＋I2（气）

1mol•L‾1   0.5mol•L‾1  0.5mol•L‾1

NH4I分解共生成HI：1mol•L‾1+4mol•L‾1=5mol•L‾1

NH4I（气）NH3（气）＋HI（气）

5mol•L‾1    5mol•L‾1

NH3的浓度为5mol•L‾1，故D项正确。

单项选择题

直肠癌垂直定位照射野的上界放在（）

A、腰4上缘 

B、腰4 

C、腰4下缘 

D、腰5上缘 

E、腰5下缘
查看答案
单项选择题

The following data sufficiency problems consist of a question and two statements, labeled (1) and (2), in which certain data are given. You have to decide whether the data given in the statements are sufficient for answering the question. Using the data given in the statements plus your knowledge of mathematics and everyday facts (such as the number of days in July or the meaning of counterclockwise), you must indicate whether.

In the figure above, is AB＞BC ？（）(Note: Figure not necessarily drawn to scale.)

(1) AB＞CD

(2) (AD-AB)＞(AD-BC)

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient.
查看答案