问题 填空题

托盘天平的两边分别放盛有一定量等同质量分数、等同体积稀盐酸的小烧杯,天平平衡,分别向两烧杯中加入等同质量的镁和锌,充分反应后,天平仍平衡,则在上述反应中一定全部反应的是______;一定有剩余的是______;可能有剩余的是______.

答案

根据一定量金属完全反应放出放出氢气质量=

金属的化合价
金属的相对原子质量
×金属的质量,由于在与盐酸反应时金属镁和锌都呈+2价而镁的相对原子质量小于锌,可知质量相等的镁和锌若完全反应,所放出氢气的质量一定不相等,天平则不会保持平衡;因此,由充分反应后天平仍平衡可判断放出氢气质量一定相等,稀盐酸一定完全反应,而等质量金属镁放出氢气质量大于锌,则金属镁一定没有完全反应而有剩余,金属锌可能有剩余也可能恰好完全反应;

故答案为:稀盐酸;Mg;Zn.

单项选择题 共用题干题
阅读理解

My dream ended when I was born. Although I never knew it then, I just held on to something that would never come to pass. Dreams really do exist. But in the morning when you wake up, they are remembered just as a dream. That is what happened to me.

I always had the dream to dance like a beautiful ballerina(芭蕾舞女演员)turning around and around and hearing people applaud for me. When I was young, I would turn around and around in the fields of wildflowers that grew in my backyard. 

Reality woke me up when I heard someone saying, "I don't know why you bother trying to dance. Ballerinas are pretty and slender(苗条) girls. Besides, you don't have the talent to even be a ballerina." I remember how those words hurt every feeling in my body. I fell to the ground and wept for hours. 

I enjoyed hanging out by the water. I would sit there for hours and stare at my reflection(倒影). There I was, looking nothing like a pretty ballerina dancer. Reflections don't lie. Once the waves would come, my reflection was washed away just like my dream to dance.

As I grew older, I began to realize that the reason my dream was even born was because it was something that was inside of me. The dream I had was never nurtured(培育) and cared for, so it slowly died. It's not that I wanted it to die, but I allowed it to die the day I started listening to the words, "You can't do it." When I finally woke up from many years of dreaming, I realized that you can't only settle for dancing in the wildflowers, you have to move on to the platform.

小题1: Which of the following can serve as the best title for the passage?

A.Care for your dream

B.Dream and reality

C.Nothing is impossible

D.Efforts to be a ballerina will pay 小题2:The author didn’t realize her dream of being a ballerina mainly because_______.

A.she was bored of dancing and performing

B.she had lack of self-respect

C.her health conditions allowed her dream to die

D.she was deeply affected by others easily小题3:From the passage, it can be inferred that _________.

A.the author was once a pretty and slender girl with wonderful dream.

B.we should dare to give up our dream facing much pressure and difficulty

C.if you stick to your dream and never say die, you will enjoy a bright life

D.You should necer give up.小题4:What is the main purpose of writing the passage?

A.to complain

B.to praise

C.to warn

D.to criticize小题5:The underlined expression “settle for” in the last paragraph means_________.

A.turn down

B.take up

C.give up

D.settle down