问题 选择题

煤气中添加少量有特殊臭味的乙硫醇(C2H5SH)可提示煤气是否泄漏.乙硫醇在煤气燃烧过程中也可充分燃烧,化学方程式为2C2H5SH+9O2

 点燃 
.
 
4CO2+2X+6H2O.下列叙述不正确的是(  )

A.X为SO2

B.乙硫醇由三种元素组成

C.乙硫醇的相对分子质量为62g

D.乙硫醇不充分燃烧也可能产生CO

答案

A、根据质量守恒定律中原子的种类与数量可知:方程式的左边有4个碳原子、12个氢原子、2个硫原子和18个氧原子,右边有4个碳原子、12个氢原子、14个氧原子和2个X分子.根据质量守恒定律中元素种类不变及原子个数不变可知:2个X分子含有2个硫原子和4个氧原子,即1个X分子含有1个硫原子和2个氧原子.因此X的化学式为SO2,故A叙述正确;

B、根据乙硫醇的化学式可以知道在乙硫醇中含有:碳、氢、硫三种元素,故B叙述正确;

C、相对分子质量的单位是“1”而不是g,只是“1”通常不写出,故C叙述不正确;

D、乙硫醇含有碳元素,根据碳在不完全燃烧时要产生一氧化碳,可以推知乙硫醇在发生不完全燃烧时也可能产生一氧化碳,故D叙述正确.

故选C.

填空题
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How do you enter a room full of strangers? Do you walk right in full of confidence? Or do you try to slip in without being noticed? ___小题1:___
In life, we admire those who do their tasks confidently. We prefer people who appear to know what they are doing. But where does that confidence begin?
Developing self-confidence starts very early. It’s parents’ role to get kids on the right track toward becoming confident people. ___小题2:___ That can be done by focusing on the child’s strengths. Parents should encourage their children to try new things and take risks. When children make mistakes, their parents should still let them know that they are loved. Children whose parents do these things will likely develop into confident adults. ___小题3:___ So what’s the solution?
◎  With most things in life, practice makes perfect, and that is true of confidence skills. ___小题4:___
◎  Always hold your head high and look people in the eye. Answer questions clearly and confidently.
◎  Focus on the things that you do well, and look for opportunities to use those abilities.
◎  Prepare thoroughly for every project. You’ll approach the task more confidently knowing that you are ready.
◎  ___小题5:___ It could be a good test score or a prize from a contest. Remind yourself that one success often leads to the next.
However, all humans fail at times, and you will too. Even with efforts to try all the above, you will never be perfect. But you can learn to love and accept yourself and live your life with confidence.
A. Keep in mind an item that reminds you of a recent success.
B. The more you practice them, the easier they will become.
C. The way you go into new situations show your level of self-confidence.
D. Our goal is to prepare students to go into the world with confidence.
E. To help that process, parents should always offer more praise than criticism.
F. Learning from mistakes helps you face the same situation later without fear.
G. But self-confidence still doesn’t come easily.