问题 填空题

氢气是一种新型的绿色能源,又是一种重要的化工原料.

(1)氢气燃烧热值高.实验测得常温常压下,1g H2完全燃烧生成液态水,放出142.9kJ热量,则表示H2的标准燃烧热的热化学方程式为:______.

(2)氢氧燃料电池能量转化率高,具有广阔的发展前景.用氢氧燃料电池进行下图所示实验(其中下图中电极均为惰性电极):该氢氧燃料电池中,b极的电极反应式为______;d极的电极反应式为______;若标准状况下氧气消耗为5.6L,则导线中转移的电子的物质的量为______.

答案

(1)根据热化学方程式的含义,H2的标准燃烧热的热化学方程式为:H2(g)+1/2O2(g)=H2O(l)△H=-285.8 kJ/mol,

故答案为:H2(g)+1/2O2(g)=H2O(l)△H=-285.8 kJ/mol;

(2)在氢氧燃料电池中,通入氢气的电极b为负极,发生氧化反应,在碱性环境下,电极反应为:H2+2e-+2OH-=2H2O,通入氧气的电极为正极,发生还原反应O2+2H2O+4e-=4OH-,和电源的负极相连的c是阴极,所以d是阳极,该机的电极反应式为:4OH--4e-=O2+2H2O,若标准状况下氧气消耗为5.6L即0.25mol,据反应O2+2H2O+4e-=4OH-,导线中转移的电子的物质的量为1mol,故答案为:H2+2e-+2OH-=2H2O;4OH--4e-=O2+2H2O;1mol.

阅读理解

     Christmas was just a week away and I had five people left to shop for but only three dollars.

     "Let's set a price limit on our gifts this year,"I suggested to my best friend Joanie.

     "That's a good idea," Joanie agreed. "How about something over five dollars?"

     "How about sixty cents?" I felt like the biggest cheapskate in the world.

     "I guess this is where I'm supposed to say it's not the gift but the thought that counts," Joanie smiled.

      It is almost impossible to buy anything under sixty cents, so it was really going to have to be very

small gifts with very big thoughts.

      Finally, Christmas Day arrived. I gave my mother a candle with a note that said, "You are the

brightest light in my life." She almost cried when she read the note.

      Igave my brother a wooden ruler. On the back of it I had painted, "No brother in the world could

measure up to you." He gave me a bag of sugar and wrote on it, "You're my sweet sister."

      For Joanie, I painted a pair of shoes with a note that said, "No one could ever fill your shoes. "She

thanked me and said I always tickled (使……高兴) her and made her laugh.

     To my other two friends, I gave Annie a paper fan and a note on it, "I'm your biggest fan." I gave

Helen a calculator that cost one dollar and I painted a message on the back, "You can always count

on me."

      My mother knows she is the most important person in my life. My brother thinks I'm sweet. Joanie

thinks I'm funny and make her laugh, which is important because her dad moved away last year and she

misses him and is sad sometimes...

1. When Christmas neared, the author worried that she________.

A. had few friends to give her gifts

B. had little money to buy gifts for others

C. didn't know what gifts her friends would like

D. didn't have enough time to go shopping

2. The underlined word "cheapskate" in Paragraph 4 probably    refers to a person who________.

A. is the poorest in the world

B. buys the cheapest skateboards

C. spends as little money as possible

D. buys the cheapest things in the world

3. The girl gave her mother a candle because it stands for________.

A.  the girl's own life

B. her mother's life

C. the girl's role in her mother's life

D.  the mother's role in the girl's life

4. What can we learn from the passage?

A. It is an art to choose gifts.

B. It is the thought not the gift that matters.

C. How to choose cheap gifts.

D. Giving gifts improves friendships.

单项选择题