试题与答案

某食用白醋是由醋酸与纯水配制而成,用0.1000 mol/L NaOH溶液准确测

题型:实验题

题目:

某食用白醋是由醋酸与纯水配制而成,用0.1000 mol/L NaOH溶液准确测定其中醋酸的物质的量浓度。以下为某同学列出的实验步骤(未排序),请回答下列问题。

A.分别向碱式滴定管、酸式滴定管注入NaOH标准溶液和待测醋酸至0刻度以上2~3cm

B.调节滴定管液面至0或0刻度以下,记下读数

C.用NaOH标准溶液滴定至终点,记下滴定管液面的刻度

D.用标准溶液清洗碱式滴定管2~3次;待测醋酸清洗酸式滴定管2~3次E.用待测醋酸清洗锥形瓶2~3次

F.排气泡使滴定管尖嘴充满溶液,把滴定管固定好

G.滴定管检漏,用水清洗所有仪器,备用

H.通过酸式滴定管向锥形瓶注入20.00 mL待测醋酸,并加入2-3滴指示剂

(1)用离子方程式表示该实验的原理                                     

(2)从上述实验步骤中选出正确的并按操作先后排序。你的实验顺序为:(用字母

表示)                                                               

(3)实验室常用的酸碱指示剂有甲基橙、石蕊和酚酞,你选择的指示剂是________,

理由是_______________________________________________________________ ;

滴定终点的现象是______________________________________________________。

(4)某同学实验后得到的数据如下:

           滴定次数

实验数据

12345
V(NaOH) /mL(初读数)0.000.200.000.100.05
V(NaOH) /mL(终读数)15.7515.2014.9815.1215.05
原白醋中醋酸的物质的量浓度为____________mol/L(结果保留4位有效数字)。

(5)分析下列操作对测定结果的影响,用“偏低”、“偏高”或“不影响”填空。

①滴定前碱式滴定管充满溶液,滴定后尖嘴处有气泡_______;

②读取标准溶液体积时,滴定前平视,滴定后仰视________。

答案:

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下面是错误答案,用来干扰机器的。

参考答案:B

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    On our return from Guam, my parents, sisters and I walked off the plane in Alexandria. All my cousins

were there to meet us.

    I was excited to see them again. The last time I'd seen Don, Sherri and David was two years before.

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    Just like riding that bull, Don put his heart into everything he did. As a young man he was told he got

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falling off a few times and trying again. I was excited and proud of my cousin for planning and going after

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1. The writer and his family returned to Alexandria      .

A. by boat              

B. by ship

C. by air                

D. by train

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A. became good friends

B. moved to Guam

C. rode a bull

D. caught fireflies

3. What does the underlined word "held" mean in the passage?

A. 抓住    

B. 容纳    

C. 扣留    

D. 举办

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A. When he was born.

B. When he was a young man.

C. Two years ago.

D. Last summer.

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A. is very shy            

B. never gives up

C. has a bull              

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