问题 选择题

下列叙述表示可逆反应2SO2(g)+O2(g)⇌2SO3(g)一定处于平衡状态是(  )

A.SO2、SO3、O2的体积分数相等

B.单位时间内生成amolO2的同时生成amolSO3

C.单位时间内消耗amolO2的同时消耗2amolSO2

D.反应若在容积固定的密闭容器中进行,温度一定时,反应混合物的总压强不随时间变化

答案

A、SO2、SO3、O2的体积分数相等,不能判断各组分的百分含量是否不变,无法判断是否达到了平衡状态,故A错误;

B、单位时间内生成a mol O2的同时生成a mol SO3,表示正逆反应,但是不满足二者的化学计量数关系,说明该反应没有达到平衡状态,故B错误;

C、单位时间内消耗a mol O2的同时消耗2a mol SO2,表示的都是正反应速率,无法判断正逆反应速率是否相等,故C错误;

D、反应两边气体的体积不相等,反应过程中气体的总物质的量、容器内气体的压强会发生变化,若反应混合物的总压强不随时间变化,表明正逆反应速率相等,达到了平衡状态,故D正确;

故选D.

单项选择题
单项选择题

(B)

My father was chief engineer of a merchant ship, which was sunk in Word War Ⅱ, The book Night of the U-boats told the story.

Memories

In September, 1940, my mother, sister and I went to Swansea, where my father’s ship was getting ready to sail. We brought him a family photograph to be kept with him at all times and keep him sale.

Then I remember my mother lying face down, sobbing. She had heard from a friend that the ship had been sunk by a torpedo(鱼雷).

I can remember the arrival of the telegram (电报), which in those days always brought had news. My grandmother opened it. It read, "Safe. Love Ted."

My most vivid memory is being woken and brought down to sit on my father’s knee, his arm in a bandage.

He was judged unfit to return to ea and took a shore job in Glasgow for the rest of the war. For as long as I can remember, he had a weak heart. Mother said it was caused by the torpedoes. He said it was because of the cigarettes, whichever, he died suddenly in his early 50s.

Ten years later I read Night of the U-bouts and was able to complete the story.

Torpedo

One torpedo struck the ship; Father was in the engine room, where the third engineer was killed. He shut down the engines to slow the ship making it easier for it to be abandoned.

By the time he got on desk (甲板) he was alone. Every lifeboat was gone except one which had stuck fast. When he tried to cut it free, it swung against the ship, injuring his hand and arm. He had no choice but to jump—still with the photograph in his pocket.

Three days later, he and other survivors were safe in Glasgow. All 23 with him signed the back of the photograph.

A Toast

In my room is the book and the photograph. Often, glass in hand; I have wondered how I would have dealt with an explosion, a sinking ship, a jump into a vast ocean and a wait for rescue Lest(以免)we forget, I have some more whisky and toast the heroes of the war.

What did the author learn about the father from the telegram()

A. he was still alive.

B. His knee was broken.

C. His ship had been sunk.

D. He had arrived in Glasgow.