【单选题】【消耗次数：1】
某学生做乙醛还原性的实验，取2mL 1mol?L﹣1的硫酸铜溶液和4mL 0.4mol?L﹣1的氢氧化钠溶液，在一个试管内混合后，加入0.5mL 40%乙醛溶液加热至沸，无砖红色沉淀．实验失败的原因是（ ）。
①
乙醛溶液太少
②
加热时间不够
③
NaOH不够量
④
CuSO4不够量
参考答案：
复制
纠错
相关题目
【单选题】
从1L 1mol/L NaCl溶液中分别取出100ml、10ml和1 ml,它们的物质的量浓度分别（ ）、（ ）、（ ）mol/L。
①
10 ,1 ,0.1
②
1 ,1 ,1
③
2, 2, 2
④
100,10 ,1
【单选题】
10.0mL 0.10 mol·L-1NaOH与20.0mL0.10 mol·L-1HCl混合，所得溶液的pH值约为
①
1.00
②
1.60
③
7.00
④
9.25
【单选题】
两步滴定法测定阿司匹林片的含量时，每1ml氢氧化钠溶液（0.1mol/L）相当于阿司匹林（分子量＝180.16）的量是：
①
18.02mg
②
180.2mg
③
90.08mg
④
45.04mg
⑤
450.0mg
【单选题】
在相同温度时100mL 0.01mol/L的醋酸溶液与10mL 0.1mol/L的醋酸溶液相比较，下列数值前者大于后者的是（）。
①
<img class="kfformula" src="20200706/1594029717591855.png" data-latex="{CH}_{3}COOH" width="102" height="37"/>的物质的量
②
电离程度
③
中和时所需NaOH的量
【单选题】
有0.1mol/L<img class="kfformula" src="20200707/1594087695131974.png" data-latex="{Na}_{2}{SO}_{4}" width="77" height="30"/>溶液300mL,0.1mol/L<img class="kfformula" src="20200707/1594087695248793.png" data-latex="{MgSO}_{4}" width="70" height="30"/>溶液200mL和0.1mol/L<img class="kfformula" src="20200707/1594087695350060.png" data-latex="{Al}_{2}{({SO}_{4})}_{3}" width="83" height="31"/>溶液100mL,这三种溶液中硫酸根离子物质的量浓度之比是（ ）。
①
1:1:1
②
1:1:3
③
3:2:3
④
3:2:2
【单选题】
向一定量的下列物质的溶液中逐滴加入氢氧化钠溶液，先生成白色沉淀，后沉淀逐渐溶解，这种物质是( )。
①
<img class="kfformula" src="20200629/1593415849981401.png" data-latex="MgS{O}_{4}" width="76" height="31"/>
②
<img class="kfformula" src="20200629/1593415849559692.png" data-latex="{A1C1}_{3}" width="58" height="33"/>
③
<img class="kfformula" src="20200629/1593415849925071.png" data-latex="{FeC1}_{3}" width="58" height="35"/>
④
<img class="kfformula" src="20200629/1593415849354494.png" data-latex="NaA1{0}_{2}" width="69" height="36"/>
【单选题】
下列溶液中的<img class="kfformula" src="20200706/1594021125433964.png" data-latex="c({C1}^{-})" width="56" height="30"/>与50mL 1mol/L氯化钠溶液中<img class="kfformula" src="20200706/1594021125862918.png" data-latex="c({C1}^{-})" width="66" height="31"/>相等的是（ ）。
①
150mL 1mol/L NaCl 溶液
②
75mL 2mol/L <img class="kfformula" src="20200707/1594088288421797.png" data-latex="{CaCl}_{2}" width="66" height="30"/>溶液
③
150mL 3mol/L KCl 溶液
④
75mL 1mol/L<img class="kfformula" src="20200707/1594088288381919.png" data-latex="{FeCl}_{2}" width="62" height="30"/> 溶液
随机题目
【单选题】
10.A discount will be offered to _____ customers to the store.
①
usual
②
ordinary
③
regular
④
old
【单选题】
17. Realizing the immense international pressure, the President_____ stepped down.
①
conspicuously
②
gracefully
③
lonely
④
. truly
【单选题】
2. Whenever I called in on Paul, he _______ on the phone.
①
talked
②
is talking
③
was talking
④
will talk
【单选题】
3. He ______ hard until I told him to sit down and have a break.
①
was working
②
had been working
③
worked
④
has worked
【单选题】
19. He tried to _____ from his memory what he knew of his former neighbor..
①
think of
②
remember
③
summon
④
gave way
【单选题】
14. Mary is _______ to what others think of her.
①
sensitive
②
sensational
③
sensory
④
sensible
【单选题】
11 ______, they had no chance of winning.
①
brave as they fought
②
bravely as they fought
③
If they fought bravely
④
Since they fought bravely
【单选题】
15. She suffered great mental_____ after her husband died, and as a result she became mad.
①
anger
②
. discomfort
③
unhappiness
④
anguish
【单选题】
13. The supervisor appreciates ______ so hard in the office.
①
for your working
②
your working
③
you to work
④
for you to work