问题 填空题

过氧化银(Ag2O2)是银锌碱性电池正极的活性物质,可通过下列反应制备:

△K2S2O8+2AgNO3+4KOH═Ag2O2↓+2KNO3+2K2SO4+2H2O.

(1)已知Ag的原子序数为47,写出Ag基态原子的核外电子排布式______,Ag在周期表中的位置______.

(2)制备Ag2O2的反应进行完全后,经______、洗涤、______等操作,即可得到Ag2O2固体,检验Ag2O2是否洗涤干净的方法是______.

(3)一种银锌(Ag2O2、Zn)碱性电池的电解质溶液为KOH溶液,电池放电时正极有Ag生成,负极有化合物A(只含有Zn、K、O)生成.化合物A中,钾、锌两种元素的质量比为78:65.则该电池的总反应方程式为______.

(4)用银锌电池电解尿素[CO(NH22]的碱性溶液可制取H2,其装置如图所示(电解池中隔膜仅阻止气体通过,M、N均为惰性电极).

①N极与银锌电池的______(填“Zn”或“Ag2O2”)极相连.

②M极的电极反应式为______.

答案

(1)元素的质子数可知电子数为47,核外各电子层电子数为2、8、18、18、1,即[Kr]4d105S1或1S22S22P63S23P63d104S24P64d105S1,电子层数等于周期数,最外层电子数等于族序数,所以位于第五周期IB族,

故答案为:[Kr]4d105S1或1S22S22P63S23P63d104S24P64d105S1;第五周期IB族;

(2)固体和液体的分离采用过滤的方法,然后再洗涤干燥,即可得到固体物质;检验是否洗涤完全,可取最后一次滤液,检验溶液中是否含有SO42-,滴入1~2滴BaCl2溶液,若不出现白色浑浊,表示已洗涤完全,

故答案为:过滤、干燥;取最后一次洗涤液少许,加入几滴BaCl2溶液,如有白色浑浊产生,说明未洗涤干净,如无现象,说明已洗涤干净;

(3)电池放电时正极的Ag2O2转化为Ag,化合物A中,钾、锌两种元素的质量比为78:65,化合物A只含有Zn、K、O,原子个数之比等于化学式中原子数之比,所以负极的Zn转化为K2ZnO2,反应还应有KOH参加,该反应的方程式为Ag2O2+2Zn+4KOH+2H2O=2K2Zn(OH)4+2Ag,

故答案为:Ag2O2+2Zn+4KOH=2Ag+2K2ZnO2+2H2O;

(4)①根据装置中的产物,知道该电池反应时中,氮元素化合价由-3价变为0价,H元素化合价由+1价变为0价,则氮元素被氧化,氢元素被还原,所以生成氮气的电极M是阳极,生成氢气的电极N是阴极,银锌电池中,负极是金属锌,阴极是和负极锌极相连的极,故N极与银锌电池的锌极相连,

故答案为:Zn;

②M是阳极,该极发生失电子的氧化反应,该极上的电极反应式为:CO(NH22-6e-+80H-=N2↑+CO32-+6H2O,

故答案为:CO(NH22-6e-+80H-=N2↑+CO32-+6H2O.

单项选择题
单项选择题

Imagine eating everything delicious you want with none of the fat. That would be great, wouldn’t it

New "fake fat" products appeared on store shelves in the United States recently, but not everyone is happy about it. Makers of the products, which contain a compound called olestra, say food manufacturers can now eliminate fat from certain foods. Critics, however, say the new compound can rob the body of essential vitamins and nutrients and also cause unpleasant side effects in some people. So it’s up to consumers to decide whether the new fat-free products taste good enough to keep eating.

Chemists discovered olestra in the late 1960s, when they were searching for a fat that could be digested by infants more easily. Instead of finding the desired fat, the researchers created a fat that can’t be digested at all.

Normally, special chemicals in the intestines (肠道) "grab" molecules of regular fat and break them down so they can be used by the body. A molecule of regular fat is made up of three molecules of substances called fatty acids.

The fatty acids are absorbed by the intestines and bring with them the essential vitamins A, D, E and K. When fat molecules are present in the intestines with any of those vitamins, the vitamins attach to the molecules and are carried into the bloodstream.

Olestra, which is made from six to eight molecules of fatty acids, is too large for the intestines to absorb. It just slides through the intestines without being broken down. Manufacturers say it’s that ability to slide unchanged through the intestines that makes olestra so valuable as a fit substitute. It provides consumers with the taste of regular fat without any bad effects on the body. But critics say olestra can prevent vitamins A, D, E and K from being absorbed. It can also prevent the absorption of carotenoids (类胡萝卜素), compounds that may reduce the risk of cancer, heart disease, etc.

Manufacturers are adding vitamins A, D, E and K as well as carotenoids to their products now. Even so, some nutritionists are still concerned that people might eat unlimited amounts of food made with the fat substitute without worrying about how many calories they are consuming.

The result of the search for an easily digestible fat turned out to be ()。

A. just as anticipated

B. commercially useless

C. quite unexpected

D. somewhat controversial