问题 实验题

某化学学习小组同学根据实验室现有的制取氨气的药品,设计了右图所示的实验装置(部分夹持仪器未画出),制取并探究氨气的还原性、检验反应产物。请回答下列问题:

(1)A中发生反应的化学方程式是                                             

(2)B中碱石灰的作用是                                                   

(3)C中黑色固体变红,且产生的气体对空气无污染,写出该反应的化学方程式                   

D中发生的现象是________________________________________________________________________。

(4)该装置存在明显缺陷,该缺陷是                         

(5)工业中常用氮气与氢气在高温、高压、铁触媒做催化剂的条件下合成氨气,该小组同学模拟该条件也合成出了氨气。已知起始时,将2 mol N2、6 mol H2充入一个容积为2 L的密闭容器中发生反应,过了5 min后,混合气体的总物质的量减少了1 mol,求在这段时间内以H2表示的化学反应速率

                         

答案

(1)Ca(OH)2+2NH4ClCaCl2+2NH3↑+2H2O(2分);

(2)干燥氨气(1分);

(3)3CuO+2NH3 3Cu+N2+3H2O(2分);无水硫酸铜变蓝(1分);

(4)缺少尾气处理装置(1分);

(5)0.15 mol/(L·min)(2分)

题目分析:(1)装置A是制备氨气的,因此其中发生反应的化学方程式是Ca(OH)2+2NH4ClCaCl2+2NH3↑+2H2O。

(2)由于生成的氨气中混有水蒸气,会干扰后续实验中产物水的测定,碱石灰是干燥剂能吸收水蒸气,所以碱石灰的作用是干燥氨气,防止干扰产物水的测定。

(3)黑色CuO变为红色,所以生成物是铜;同时生成一种无色气体,该气体无污染,因此该气体是氮气。根据原子守恒可知,还有水生成,则反应的化学方程式为3CuO+2NH3 3Cu+N2+3H2O。无水硫酸铜易吸水由摆手舞变为蓝色,所以D中的实验现象是白色无水CuSO4粉末变为蓝色。

(4)氨气是刺激性气体,所以不能随意排放到空气中,应有尾气处理装置,可用如图所示装置吸收氨气

(5)合成氨反应的化学方程式为:

3H2     +    N22NH3   △n↙

3mol         1mol   2mol     2mol

n(H2)                        1mol

解得n(H2)==1.5mol

则消耗氢气的浓度是1.5mol÷2L=0.75mol/L

因此在这段时间内以H2表示的化学反应速率=0.75mol/L÷5min=0.15 mol/(L·min)

单项选择题
单项选择题

Motherhood may make women smarter and may help prevent dementia in old age by bathing the brain in protective hormones, US reseachers reported on Thursday.

Tests on rats show that those who raise two or more litters of pups do considerably better in tests of memory and skills than rats who have no babies, and their brains show changes that suggest they may be protected against diseases such as Alzheimer’s. University of Richmond psychology professor Craig Kinsley believes his findings will translate into humans.

"Our research shows that the hormones of pregnancy are protecting the brain, including estrogen, which we know has many neuroprotective effects," Kinsley said.

"It’s rat data but humans are mammals just like these animals are mammals," he added in a telephone interview. "They go through pregnancy and hormonal changes. "

Kinsley said he hoped public health officials and researchers will look to see if having had children protects a woman from Alzheimer’s and other forms of age-related brain decline.

"When people think about pregnancy, they think about what happens to babies and the mother from the neck down," said Kinsley, who presented his findings to the annual meeting of the Society of Neuroscience in Orlando, Florida.

"They do not realize that hormones are washing on the brain. If you look at female animals who have never gone through pregnancy, they act differently toward young. But if she goes through pregnancy, she will sacrifice her life for her infant—that is a great change in her behavior that showed in genetic alterations to the brain. \

Which title is the best for this passage().

A. Do You Want to Be Smarter

B. Motherhood Makes Women Smarter

C. Mysterious Hormones

D. An Important Study