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【简答题】
对溴甲苯是合成农药溴螨酯的重要原料．工业用液溴、甲苯与1-丙醇共热合成对溴甲苯和1-溴丙烷，其原子利用率很高．实验室模拟的合成流程和相关数据如下： 已知：甲苯与溴在有水存在反应． 物质 甲苯 1-丙醇 1-溴丙烷 沸点℃ 110.8 97.2 71 物质 对溴甲苯 邻溴甲苯 沸点℃ 184.3 181.7 （1）液溴的颜色是______，实验室液溴存放试剂瓶里时应密闭保存，同时需要在瓶中加______，以减少挥发． （2）25℃恒温搅拌至溴的颜色完全褪去时完成甲苯的溴代反应．搅拌的目的是______．加入水的作用是：易于控制温度；______． （3）加热搅拌操作中加入浓硫酸，搅拌，完成1-丙醇的取代反应，加入浓硫酸的作用是______，加热微沸2小时的目的是______ （4）操作Ⅰ的名称是______洗涤操作应在______（填写仪器名称）中进行． （5）经以上分离操作后，粗对溴甲苯中还含有的最主要杂质为______（填写名称），使用操作Ⅱ分离出1-溴丙烷的原理是______． （6）分离出的水溶液中含HBr、H 2 SO 4 和Fe 3+ 离子，将水溶液稀释定1000mL，取20.00mL，加入几滴甲基橙作指示剂，用一定浓度的NaOH溶液滴定，测定出HBr的物质的量明显低于理论值，原因是______；有同学认为无需加入指示剂，也能完成滴定，提出这一观点的理由是______．
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举一反三
【多选题】Considering a claim against the makers or sellers, what shall we think first?
A.
how much you paid for the product
B.
how much you have used it
C.
how much do you know about the product
D.
contact info
【简答题】1851年“水晶宫”博览会之后，英国的（）倡导了“（）”
【多选题】简支梁受力发生弯曲变形,以下说法正确的有 。
A.
截面1-1和6-6的弯矩都为零
B.
截面2-2和3-3的弯矩相等
C.
截面4-4和5-5的弯矩不相等
D.
截面1-1和2-2的剪力相等
【单选题】听力原文： A British rower has set a record for the slowest-ever Atlantic crossing, coming ashore in southern England 124 days after leaving North America. The time was a disappointment, considering the 23...
A.
The fastest person to cross the Atlantic.
B.
The youngest person to row an ocean alone.
C.
The person who makes the fastest west-to-east crossing.
D.
The person who stays on the ocean for the longest time.
【单选题】简支梁受力如图,下列说法正确的是( )
A.
1-1截面的弯矩为零,3-3截面的弯矩为零;
B.
1-1截面的弯矩为-12kN.m,3-3截面的弯矩为零;
C.
1-1截面的弯矩为12kN.m,3-3截面的弯矩为零;
D.
3-3截面的弯矩不为零。
【单选题】简支梁受力如图,下列说法正确的是( )
A.
1-1截面的剪力与3-3截面的剪力相等;
B.
2-2截面的剪力与3-3截面的剪力相等;
C.
1-1截面的剪力与2-2截面的剪力相等;
D.
1-1截面、2-2截面、3-3截面的剪力均相等。
【简答题】April Fool's Day 1st April is a day __1__, / or you could easily __2__ someone. / The origin of the day is __3__ with the change / in the calendar in the 16th __4__, / which __5__ that 1st April was n...
【单选题】Luckily, the tower survived, and its tilt has made it an Italian icon, attracting visitors from all over who flock to Pisa to see one of the greatest architectural oddities in the world. __________ By...
A.
Yes, because it provides an important restatement of the main claim in the previous sentence.
B.
Yes, because it establishes an important shift in emphasis in the paragraph’s discussion about the tower’s tilt.
C.
No, because it interrupts the paragraph’s discussion with irrelevant information.
D.
No, because it repeats information that is already presented in the first paragraph.
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