溶质相同、质量分数为a%和b%的两份溶液质量分别为mg、ng，将两份_爱下问搜题

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问题选择题

溶质相同、质量分数为a%和b%的两份溶液质量分别为mg、ng，将两份溶液混合并蒸发去xg水，所得溶液的物质的量浓度为c mol/L。关于求溶质的摩尔质量，下列说法正确的是（）

A．只要知道蒸发后所得溶液的密度（ρ）,就能求出溶质的摩尔质量

B．只要知道混合前两份溶液的物质的量浓度（c）,就能求出溶质的摩尔质量

C．只要知道蒸发前混合液的体积（V）,就能求出溶质的摩尔质量

D．以上说法都不正确。

答案

答案：D

混合液中的溶质如果是易挥发或分解的，就无法求出溶质的摩尔质量。

单项选择题

关于影响生物转化的因素的叙述，错误的是

A．肝功能低下可影响生物转化功能

B．药物或毒物本身的诱导作用

C．几种药物同服可能出现抑制作用

D．会受到年龄和性别的影响

E．不受年龄和性别的影响

完形填空

It happened towards evening, when I was resting in a cafe. I 36 a pair of newly bought white leather shoes, which were rather expensive. Then 37 came to me.
He was in an unfit shirt, 38 pale and weak. He looked about eleven or twelve. No sooner39 begun to speak than he opened the box in his hand and took out the tools of shoe-polishing. He bent down, 40 my leather shoes, and began to shine them.
He was concentrating on his job when heavy rain began to pour 41 . People rushed into the cafe for protection from the 42 . More and more people crowded in and gradually 43 the boy from me.
Hours passed, and 44 turned dark. I had no shoes on my feet and wondered 45 the boy had been. I thought he would not 46 my leather shoes, and I would have to walk back home on 47 in the night.
When it was near midnight the rain 48 , people started to go out. The cafe 49
Closed. I had to move to the door, I was surprised to see the boy sleeping on the floor with his head leaning 50 a box. He held a package made of his shirt tightly in his arms.
I 51 him slightly and woke him up. He jumped up and rubbed his eyes for a while before he 52 me. Then he opened the 53 hurriedly, gave me my leather shoes, and apologized to me shyly.
I paid him and wrapped around him his unfit shirt, which 54 my leather shoes.
After saying goodbye to the boy, I was 55 home, with the image of the boy staying in my mind.

C．my bare feet

D．my own foot

A．was wrapping

B．was wrapped

C．had wrapped

A．on the way to