问题 问答题

图是某试剂瓶标签的部分内容.

(1)该溶液敞口放置一段时间后会变稀,原因是什么?

(2)要配制100g9.8%的稀疏酸,需要这种浓硫酸的体积为______mL(精确到0.1mL).

(3)不小心将浓硫酸沾到皮肤上,适当处理后还要涂上3%~5%的碳酸氢钠溶液.写出碳酸氢钠与硫酸反应的化学方程式.

答案

(1)浓硫酸具有吸水性,敞口防止一段时间后,能吸收水分而使溶液中的水分(溶剂)增多,溶质质量不变,故溶质的质量分数变小(即溶液变稀).

(2)设需要这种浓硫酸的体积为x,根据溶液稀释前后,溶质的质量不变,

则100g×9.8%=1.84g/cm3×x×98% x=5.4cm3=5.4mL.

(3)碳酸氢钠与稀硫酸反应生成硫酸钠、水、二氧化碳,反应的化学方程式为:2NaHCO3+H2SO4=Na2SO4+2CO2↑+2H2O.

故答案为:(1)浓硫酸具有吸水性,敞口防止一段时间后因吸收水分而使溶液中的水分(溶剂)增多,溶液变稀.

(2)5.4.

(3)2NaHCO3+H2SO4=Na2SO4+2CO2↑+2H2O.

阅读理解

阅读理解。

     Once Effendi had a joke with the Prime Minister (宰相). He said that the Minister would die the next day.

The next day, the Minister fell to the ground from the horse and really died. When the king learned this, he got

angry and sent his men to catch Effendi at once.

     When Effendi was brought to him, the king shouted angrily, "Effendi, since you knew when my Minister

would die, you must know the date of your own death. Say it out, or you'll die today."

     Effendi looked at the king for a while. Then he answered,"But how can I know? I'll die two days earlier

than you." The king was afraid that if he killed Effendi, he himself would die after that. He thought he must

keep Effendi alive as long as possible, so he let Effendi go.

1. This story tells us __________.

A. how Effendi fooled the king

B. when the king would die

C. why the Minister died

D. Effendi knew the date of everyone's death

2. The Prime Minister died because __________.

A. Effendi killed him

B. Effendi said he would die

C. he was badly ill

D. he fell off the horse

3. Why did the king ask Effendi to tell him the date of Effendi's own death?

A. Because the king wanted to know when he himself would die.

B. Because the king wanted to find an excuse to kill Effendi.

C. Because he himself had known the date of Effendi's death.

D. Because he wanted to know when Effendi would die.

4. The king let Effendi go because __________.

A. he hoped to live a long life

B. he was afraid of Effendi

C. he didn't believe Effendi's words

D. he knew they would die two days later

5. Which of the following is not true?

A. Effendi played a joke on the Minister.

B. The king was afraid of death.

C. Effendi didn't know when the king would die.

D. If the king killed Effendi, he himself would die two days later.

填空题