下列路由协议中管理距离是110的路由协议是()。A、RIP B、OSPF C、EIGRP

题型:单项选择题

问题:

下列路由协议中管理距离是110的路由协议是()。

A、RIP

B、OSPF

C、EIGRP

D、ISIS

考点:计算机网络管理员网络管理员综合练习网络管理员综合练习题库
题型:单项选择题

第29届北京奥运会火炬接力活动历时130天,传递行程约为137000km.用科学记数法表示137000km是 [ ]

A.1.37×105km

B.13.7×104km

C.1.37×104km

D.137×103km

题型:单项选择题

Which is safer --- staying at home, traveling to work on public transport, or working at the office? Surprisingly, each of these carries the same risk, which is very low.However, what about flying compared to working in the chemical industry? Unfortunately, the former is 65 times riskier than the latter! In fact the accident rate of workers in the chemical industry is less than that of almost any of human activity, and almost as safe as staying at home.

The trouble with the chemical industry is that when things go wrong they often cause death to those living nearby.It is this that makes chemical accidents so newsworthy.Fortunately, they are extremely rare.The most famous ones happened at Texas City (1947), Flixborough (1974), Seveso (1976), Pemex (1984) and Bhopal (1984).

Some of these are always in the minds of the people even though the loss of life was small.No one died at Seveso, and only 28 workers at Flixborough.The worst accident of all was Bhopal, where up to 3,000 were killed.The Texas City explosion of fertilizer killed 552.The Pemex fire at a storage plant for natural gas in the suburbs of Mexico City took 542 lives, just a month before the unfortunate event at Bhopal.

Some experts have discussed these accidents and used each accident to illustrate a particular danger.Thus the Texas City was caused by tons of ammonium nitrate, which is safe unless stored in a great quantity.The Flixborough fireball was the fault of management, which took risks to keep production  going during essential repairs.The Seveso accident shows what happens if the local authorities lack knowledge of the danger on their doorstep.When the poisonous gas drifted over the town , local leaders were incapable of taking effective action.The Pemex fire was made worse by an overloaded site in an overcrowded suburb.The fire set off a chain reaction of exploding storage tanks.Yet, by a miracle, the two largest tanks did not explode.Had these caught fire, then 3,000 strong rescue team and fire fighters would all have died.

小题1:Which of the following statements is TRUE?

A.Working at the office is safer than staying at home.

B.Travelling to work on public transport is safer than working at the office.

C.Staying at home is safer than working in the chemical industry.

D.Working in the chemical industry is safer than traveling by air.小题2:Chemical accidents are usually important enough to be reported as news because       .

A.they are very rare

B.they often cause loss of life

C.they always occur in big cities

D.they arouse the interest of all the readers小题3:According to the passage, the chemical accident that caused by the fault of management happened in_________.

A.Texas city

B.Flixborough

C.Seveso

D.Mexico City小题4:From the passage we know that “ammonium nitrate” is a kind of _____.

A.natural gas, which can easily catch fire

B.fertilizer, which can't be stored in a great quantity

C.poisonous substance, which can't be used in overcrowded areas

D.fuel, which is stored in large tanks小题5:From the discussion among some experts we may conclude that _____.

A.to avoid any accident we should not repair the facilities in chemical industry

B.the local authorities should not be concerned with the production of the chemical industry

C.all these accidents could have been avoided or controlled if effective measures had been taken

D.natural gas stored in very large tanks is always safe

题型:单项选择题

与苯甲酸是重要的化工原料,可通过苯甲醛在氢氧化钠水溶液中的歧化反应制得,反应式为:

某研究小组在实验室制备苯甲醇与苯甲酸,反应结束后对反应液按下列步骤处理:

重结晶过程:溶解—→活性炭脱色—→趁热过滤—→冷却结晶—→抽滤—→洗涤—→干燥

已知:苯甲醇易溶于乙醚、乙醇,在水中溶解度较小。

请根据以上信息,回答下列问题:

(1)萃取分离苯甲醇与苯甲酸钠时,合适的萃取剂是       ,其理由是       。充分萃取并静置分层,打开分液漏斗上口的玻璃塞后,上下层分离的正确操作是        。萃取分液后,所得水层用盐酸酸化的目的是        

(2)苯甲酸在A、B、C三种溶剂中的溶解度(s)随温度变化的曲线如下图所示:

重结晶时,合适的溶剂是       ,其理由是         

重结晶过程中,趁热过滤的作用是            

洗涤时采用的合适洗涤剂是      

A.饱和食盐水                          B.Na2CO3溶液

C.稀硫酸                              D.蒸馏水

(3)为检验合成产物中苯甲酸的含量,称取试样1.220 g,溶解后在容量瓶中定容至100 mL,移取25.00 mL试样溶液,用0.1000 mol·L-1 NaOH溶液滴定,滴定至终点时NaOH溶液共消耗24.65 mL,则试样中苯甲酸的含量          

题型:单项选择题

在地面图上,水平气压梯度越小的地方,等压线()。

A.越密集

B.越稀疏

C.有的地方密集,有的地方稀疏

D.疏密与梯度无关

题型:单项选择题

C型环密封的结构的特点和适用范围是什么?C性环密封一般采用什么材料制作?

更多题库