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秀山土家族苗族自治县彩光祛痘多少钱大河指南南岸区脸部抽脂价格

2019年09月19日 02:44:14
来源:四川新闻网
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Hi, Im Jessica嗨,我是Jessicaand today Im gonna be talking about a chemical demonstration I like to call今天我要讲的化学演示叫作;mirror, mirror;;魔镜魔镜;In this demo, MITs Dr. John Dolhun will demonstrate Tollens testMIT的John Dolhun士将演示Tollens测试a chemical test created by this man, Bernard Tollens这是由这个人,十九世纪末德国化学家a German chemist born in the late 1800sBernard Tollens所发明的化学测试So lets watch Dr. Dolhun perform this demonstration here at MIT作为MIT剑桥科学节的一部分,来看看Dolhun士as part of the Cambridge Science Festival是如何演示这个的OK, so Im gonna be careful好,我要小心了and Im going to pour my first substance into the flask首先将第一种物质倒入烧瓶my second substance然后是第二种物质down to the last drop倒完最后一滴and my third substance然后是第三种物质and were going to do a little shaking摇一摇for mixing some things together让它们能够充分混合So what did Dr. Dolhun do?Dolhun士做了什么呢Well, he added three solutions to the flask他往烧瓶中添加了三种溶液Solution 1 was glucose in water溶液一是葡萄糖水溶液Solution 2 was a mixture of silver nitrate and ammonium nitrate溶液二是硝酸银和硝酸铵的混合溶液And solution 3 was sodium hydroxide溶液三是氢氧化钠which is a base一种碱So lets focus on the second two solutions first我们先来看后两种溶液When you mix solutions 2 and 3, two things happen溶液二三混合时,会发生两件事First, you form Ag20首先会形成Ag2Owhich is insoluble in water它不溶于水so it precipitates out as a brown solid会作为褐色固体沉淀出来The sodium hydroxide氢氧化钠reacts with ammonium, NH4+会同铵根离子NH反应to produce ammonia,NH3 生成氨 NH4This dissolves the precipitate这会溶解沉淀物and you end up with Ag(NH3)2最终得到Ag(NH3)2which all has a positive charge这整个带有一单位正电荷This is soluble in water and its called Tollens reagent它溶于水,叫作Tollens试剂Now the positive charge is born by the silver正电荷来自于银离子So we have in solution is essentially silver ions溶液中基本上也就是银离子Now looking at solution 1再看溶液一glucose looks like this葡萄糖是这样的We dont really care about this whole part of the molecule分子的这一部分我们并不关心So were gonna call it R可以记作Rfor the rest表示剩余部分So glucose is basically this葡萄糖可以写成这样And this part of the glucose is going to start reacting with the silver ions葡萄糖的这部分会同银离子反应Lets watch what happens看看会发生什么201501/352015长寿区妇幼保健医院瘦腿针多少钱巴南区臀部吸脂多少钱路易斯弗朗斯科向我们展示我们为什么应该去庆祝大规模,超市化的白面包。她说到,从环境需要上来讲,大规模的生产会解决粮食问题,但同时我们也应该给小规模作坊和传统方法留给它们自己的位置。201311/266107联合国世界粮食计划署长乔瑟特·希兰讲述为何在粮食供应充足的当下,人们仍然经受饥饿,仍然死于粮食匮乏,仍然使用粮食作为战争的武器。她的理想是:粮食问题不能靠个人力量来解决。我们必须联合起来。201411/339332重庆市吸脂减肥医院哪好

璧山区妇女儿童医院口碑怎么样重庆埋线双眼皮手术价格A new high-speed railway route has opened in North China, forming the last link in the high-speed rail network from the country’s north to south.一条新的高铁线路在华北开通,形成了从中国北方到南方高铁网络中的最后一链。The line goes from port city Tianjin to coastal Qinhuangdao in Hebei Province, and its first train set off on Sunday morning from Tianjin. The nearly 300 kilometers long journey only takes about an hour and ten minutes, half the time it takes by regular trains. It connects with the Beijing to Harbin and Harbin to Dalian routes to the north, and the Beijing to Shanghai route to the south.该线路由天津市开往河北省秦皇岛市,且首趟列车已于周日上午由天津出发。近300公里的路程仅耗时1小时10分钟,为普通列车一半的耗时量。该线路联通了开往北方的北京到哈尔滨,哈尔滨到大连线路,以及开往南方的北京到上海线路。201312/266844重庆儿童医院是正规的吗重庆妇幼保健激光祛太田痣多少钱

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