某学生在实验室用密度为1.18g/mL,质量分数为36.5%浓盐酸配制0.1mo

题型:实验题

问题:

某学生在实验室用密度为1.18g/mL,质量分数为36.5%浓盐酸配制0.1mol/L盐酸溶液250mL,填空并请回答下列问题:

(1)配制250mL0.1mol/L的盐酸溶液。该生用量筒量取盐酸体积_________mL,除量筒外还需要的其它仪器:_________。

(2)该学生配制前设计了下列操作,其合理的操作顺序是_________(字母表示,每个字母只能用一次)

A.用30mL水洗涤烧杯2~3次,洗涤液均注入容量瓶,振荡

B.用量筒准确量取所需体积的浓盐酸,沿玻璃棒倒入烧杯中,再加入少量水(约30mL),用玻璃棒慢慢搅动,使其混合均匀

C.将已冷却的盐酸沿玻璃棒注入容量瓶中

D.将容量瓶盖紧,倒置并振荡,摇匀

E.改用胶头滴管加水,使溶液凹面恰好与刻度相切

F.继续往容量瓶内小心加水,直到液面接近刻度1-2cm处

(3) 操作A中,将洗涤液都需移入容量瓶,其目的是:______________________。将溶液注入容量瓶前需冷却到室温,这是因为:________________________。

(4)若出现如下情况,对所配溶液浓度将有何影响(偏高、偏低或无影响)?

a.加蒸馏水时不慎超过了刻度_________;

b.定容时俯视_________;

C.在操作B中若用水洗涤量筒2-3次,并将洗涤液一并倒入烧杯中_________;

(5)若实验过程中出现如下情况应该如何处理? 向容量瓶中转移溶液时(实验步骤B) 不慎有液滴掉在容量瓶外? _________________。

考点:配制一定物质的量浓度的溶液
题型:实验题

额叶的额上回、额中回及额下回在()

A.矢状位显示最为清楚 

B.横切位显示最为清楚 

C.冠状位显示最为清楚 

D.横轴位显示最为清楚 

E.斜切位显示最为清楚 

题型:实验题

It’s not just women who wear skirts.   小题1:   In Scotland, men wear a kind of skirt called kilt. The kilt is their national dress and an important part of their tradition.

A kilt is a colored skirt reaching down to the knees. It has checks(格子)on it with different colors, like red and blue.   小题2:   

  小题3:   There are many stories about it. One story is that kilt was invented in the 1720s by an English factory owner, Thomas Rawlinson.

Thomas Rawlinson had a number of Scottish workers in his factory and he thought their clothing got in the way of their work.    小题4:    

Today, most Scotsmen look the kilt as formal dress. They usually only wear them at wedding or big dinner.     小题5:  

A.Each family in Scotland has it’s own colors.

B.There are only a few men who still wear a kilt every day.

C.How did the Scots start to wear skirts ?

D.It was important for Scots to wear skirts at any time.E.So he cut their long clothes into shorter skirts.

F.Wearing skirts is very beautiful for women.

G.Men can wear them, too.

题型:实验题

早材至晚材的变化缓急,不同树种是有差异的,例如硬松类的马尾松、油松等由早材至晚材为缓变。

题型:实验题

稀土元素主要分离方法有()。

A.分级结晶法

B.分步沉淀法

C.氧化还原法

D.离子交换法和溶剂萃取法

题型:实验题

洛伦茨曲线

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