问题 填空题

以下有水参与的化学反应都属于氧化还原反应,但水既不做氧化剂又不做还原剂的有______.

①2Na2O2+2H2O=4NaOH+O2↑              ②Cl2+H2O=HCl+HClO

③C+H2O=CO+H2                         ④3NO2+H2O=2HNO3+NO

⑤2Na+2H2O=2NaOH+H2↑                 ⑥2F2+2H2O=4HF+O2

答案

①2Na2O2+2H2O=4NaOH+O2↑反应中,Na2O2中O元素的化合价分别由-1价变化为-2价和0价,但H2O中H和O元素的化合价不变,则该反应属于氧化还原反应,但水既不做氧化剂又不做还原剂,故①正确;

②Cl2+H2O=HCl+HClO反应中,Cl2中Cl元素的化合价分为由0价变化为-1价和+1价,但H2O中H和O元素的化合价不变,则该反应属于氧化还原反应,但水既不做氧化剂又不做还原剂,故②正确;

③C+H2O=CO+H2反应中,H2O中H元素的化合价降低,不符合题目要求,故③错误;

④3NO2+H2O=2HNO3+NO反应中,NO2中N元素的化合价分别由+4价变化为+5价和+2价,但H2O中H和O元素的化合价不变,则该反应属于氧化还原反应,但水既不做氧化剂又不做还原剂,故④正确;

⑤2Na+2H2O=2NaOH+H2↑反应中,H2O中H元素的化合价降低,不符合题目要求,故⑤错误

⑥2F2+2H2O=4HF+O2反应中,H2O中O元素的化合价升高,不符合题目要求,故⑥错误.

故答案为:①②④.

听力题

阅读下面短文,根据短文内容及首字母提示,在空白处填入一个适当的单词。

A young woman in her twenties was sitting on the train, next to her mother. They both looked tired but excited.

The young woman was looking out 小题1: f_______ the train’s window. Suddenly, she shouted, “Mom, look, the trees are behind us!” Her voice was so 小题2: l________ that everyone on the train heard.

Mom smiled. 小题3: B________ a young couple who were sitting nearby looked at the young woman’s childish(孩子气的) behavior with pity. “Poor girl. There must be something wrong with her 小题4: m_________ .” they thought.

A few minutes later, the young woman shouted 小题5: a________. “Mom, look! The clouds are running with us!” Mom smiled again. And she seemed very happy with her daughter’s 小题6:w _______ that she said just now.

Finally, the couple couldn’t help asking the old woman, “Sorry if we offend(冒犯)you. But why don’t you小题7:t_________ your daughter to a good doctor?”

The old woman smiled and said, “Actually, we have just come from a hospital.”

“Then you should go to a 小题8: b_______ one. Because it seems that your daughter’s situation (状况) hasn’t improved.” said one of them. They felt so bad for the old woman.

“No, in fact I’m very happy with the treatment(治疗).” said the mother, “My daughter was blind from birth. Today, she is seeing the world for the小题9: f_______ time.”

Every single person has a story. Don’t judge(判断)people before you know小题10:t________

well. The truth might surprise you.

单项选择题