问题 填空题

某化学兴趣小组为了探索铝电极在原电池中的作用,设计并进行了以下一系列实验,实验结果记录如下:

编号电极材料电解质溶液电流计指针

偏转方向

1Mg Al稀盐酸偏向Al
2Al Cu稀盐酸偏向Cu
3Al 石墨稀盐酸偏向石墨
4Mg AlNaOH溶液偏向Mg
5Al Zn浓硝酸偏向Al
 

根据上表中的实验现象完成下列问题:

(1)实验1、2中Al所作的电极是否相同?             。 

(2)指出实验3中铝和石墨的电极名称,并写出实验中的电极反应和电池总反应。

铝为(  )         ;  石墨为(  )         。 

电池总反应:                                            。 

(3)实验4中的铝作正极还是负极?   ,为什么?             。 

答案

(1)不相同, (2)负极:2Al-6e-=2Al3+正极:6H++6e-=3H2↑总反应:2Al+6H+=2Al3++3H2↑(

(3)负极(1分)   因为Al能和NaOH溶液反应而Mg不能(2分)

题目分析:(1)实验1中,氧化还原反应发生在金属镁和稀盐酸之间,失电子的是金属镁,作负极,铝作正极;实验2中,氧化还原反应发生在金属铝和稀盐酸之间,失电子的是金属铝,铝作负极,所以实验1、2中Al所作的电极不相同;(2)Al、石墨、盐酸构成的原电池中,较活泼的金属铝做负极,电极反应为:2Al-6e-→2Al3+;石墨电极为正极,电极反应为:6H++6e-→3H2↑,总反应:2Al+6H+=2Al3++3H2↑;(3)实验4中,金属铝和氢氧化钠发生氧化还原反应,失电子的是金属铝,为原电池的负极。

完形填空

阅读下面的短文,并根据文章后的题目要求回答小题。

(1)While adults need to eat breakfast each day to perform their best, kids need it even more. Their growing bodies and developing brain rely heavily on the regular intake of food. When kids skip breakfast , they can end up going for as long as eighteen hours without food. This period of semi-starvation can create a lot of physical, intellectual, and behavioral problems for them.

(2)If you and your kids regularly skip breakfast to save time or to get a few more minutes of sleep, remember that eating a healthy morning meal will probably save your time in the long run. By recharging your brain and your body, you’ll be more efficient in just about everything you do.

(3)Interestingly, studies show that kids who skip breakfast are late for and absent from school more often than children who eat breakfast on a regular basis. Time invested in breakfast is much more valuable than the few extra minutes of sleep you might get by skipping the morning meal. If you and your kids seem unable to make time for breakfast, consider enrolling your children in a school breakfast program. If possible, pack a breakfast brown-bag the night before so that you and your kids can eat on the way to school and work.

(4)Some people skip breakfast in an effort to lose weight, but actually it is more likely to cause weight gain rather than weight loss. Skipping breakfast is strongly linked to the development of obesity. According to research, skipping meals, especially breakfast, can actually make weight control _______________. Breakfast skippers tend to eat more food than usual at the next meal or eat high-calorie snacks to get rid of hunger.

(5)To teens, especially teenage girls, skipping breakfast may seem like a perfect way to lose weight. It’s important for moms to educate their kids about the importance of the morning meal and role it plays in maintaining good health and preventing obesity.

1. What is mainly discussed in the passage? (no more than 6 words)

_______________________________________________________________________________

2. Complete the following statement with proper words. (no more than 3 words)

Sparing some time ______________ is more beneficial to you than skipping it for more sleep.

3. List three reasons why many kids and adults skip breakfast. (no more than 10 words)

_______________________________________________________________________________

4.Fill in the blank in Paragraph 4 with proper words. (no more than 4 words)

____________________________________________________________________________

5. What does the underlined word “it” in the last paragraph probably refer to? (no more than 3 words)

_______________________________________________________________________________

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