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【单选题】
What is color? Why do some objects look red, others green, others blue? Color is caused by reflected light rays. We see color because objects reflect light. Some thing that is red reflects mostly red light. In the same way, a green object reflects mostly green light. White objects reflect all colors of light. Black objects do not reflect any light. What happens to the colors of light that are not reflected? They are absorbed by the object. The darker the color, the less light is reflected and the more light is absorbed. Light that is absorbed is turned into heat. For this reason, dark-colored clothes are warmer in the sunlight than light-colored clothes. Which is the main idea of this passage?A.
Dark-colored clothes are warmer in the sunlight.
B.
Objects absorb part of the sunlight.
C.
Color is caused by reflected light rays.
D.
A red object reflects mostly red light.
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【单选题】用原子吸收法测定元素M时。由未知试样得到的吸光度为0.435,若9毫升试样中加入1毫升100mg/L的M标准溶液,测得该混合液吸光度为0.835.未知试液中M的浓度是( )mg/L。
A.
10.88
B.
4.904
C.
9.808
D.
5.406
【简答题】用原子吸收法测定元素M时。由未知试样得到的吸光度为0.435,若9毫升试样中加入1毫升100mg·L-1的M标准溶液,测得该混合液吸光度为0.835.问未知试液中M的浓度是多少mg·L-1?(不用写单位)
【简答题】用原子吸收法测定元素M时。由未知试样得到的吸光度为0.435,若9毫升试样中加入1毫升100mg·L-1的M标准溶液,测得该混合液吸光度为0.835.问未知试液中M的浓度是多少?
【简答题】用原子吸收法测定元素 M 时,由一份未知试样得到的吸光度读数是 0.435 , 在 9mL 未知液中加入 1mL 100 ug/mL 的 M 标准溶液。这一混合液得到的吸光度读数为 0.835 ,问 (1) 未知液中的 M 的质量浓度是多少? (2) 如以置信度为 3 ,其检出限为(测定 20 次的标准偏差为 0.011 )多少?
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