搜题请搜索小程序“爱下问搜题”
问题 单项选择题

NaOH溶液标签上标示的浓度为0.300mol/L，该溶液从空气中吸收了少量的CO2，现以酚酞为指示剂，用标准HCl溶液标定，标定结果比标签上标示的浓度( )。

A．高

B．低

C．不变

D．无法确定

答案

参考答案：B

阅读理解

小题1:Which of the following is experiment time?

A．8:00-22:00 on Saturday.

B．10:00-21:00 on Wednesday.

C．8:00-11:30 on Monday and Thursday.

D．18:00-21:00 on Sunday, Monday, Thursday.小题2:If you want to be a volunteer, you should _____________.

A．come from Asian countries

B．be able to get up early in the morning

C．be free at certain time next two weeks

D．call the office of the department of psychology小题3:How much will you be paid after three hours’ experiment?

A．30 yuan.

B．60 yuan.

C．90 yuan.

D．120 yuan.
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单项选择题

某学校想估计学生迟到的平均时间，经验表明迟到时间的标准差为2分钟，那么学校要以95%的置信度使估计值在真值附近0.5分钟的范围内应取的样本数为（）。

A.60

B.61

C.62

D.63
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