某实验小组为检验露置在空气中的NaOH固体是否变质并确定其组成,开展了一下探究活

题型:问答题

问题:

某实验小组为检验露置在空气中的NaOH固体是否变质并确定其组成,开展了一下探究活动.

【讨论与交流】

(1)NaOH能与空气中的______(填化学式)发生反应生成Na2CO3

(2)Na2CO3的水溶液呈碱性.

【查阅资料】

(3)NaOH在空气中不会转化成NaHCO3

(4)CaCl2、NaCl的水溶液均呈中性.

【猜想假设】猜想一:固体全部为NaOH.

猜想一:固体全部为______.

猜想二:固体为NaOH和Na2CO3的混合物.

【实验探究】将待检固体溶于水配成溶液.按以下两种方案进行实验:

方案一:用洁净的玻璃棒蘸取该溶液滴在pH试纸上,测得pH______7(填“>”、“<”或“=”),说明猜想一成立.

方案二:取该溶液少许,往其中加入足量CaCl2溶液,有白色沉淀产生;待沉淀不再产生,过滤,再往滤液中滴入酚酞试液,溶液变成______色,说明猜想三成立.

【归纳与总结】很明显,方案一的结论______(填“正确”或“错误”),理由是______.

【探究与拓展】为进一步确定原固体的组成,该实验小组的同学称取26.6g待检固体,按如图所示过程实验(步骤②产生的气体全部逸出),请参照图中提供的数据计算:

(5)26.6g固体混合物中Na2CO3的质量.

(6)所用稀盐酸中溶质的质量分数.

(7)实验最终所得351g溶液中溶质的质量分数.

考点:设计实验和科学探究物质的变质
题型:问答题

Mr. Robinson had to travel somewhere on business and as he was in a hurry, he decided to go by air. He liked to sit beside a window when he was flying. So, when he got on to the plane, he looked for a window seat. He found all of them had already been taken except one. There was a soldier sitting in the seat beside this one and Mr. Robinson was happy that he had not taken the one by the window; but, anyhow, he at once went towards it. When he reached it, however, he saw there was a notice on it. It was written in ink and said “This seat is reserved for proper load balance. Thank you.” Mr. Robinson had never seen such a notice in a plane before, but he thought that the plane must be carrying something heavy in its baggage room which made it necessary to have the passengers properly balanced, so he walked on and found another empty seat, not beside a window, to sit in. Then, when the plane was quite full, a very beautiful girl stepped into the plane. The soldier quickly took the notice off the seat beside him and in this way succeeded in having the girl beside him during the whole trip.

小题1:When he got on the plane he was happy to find that _______.

A.a notice was put in a window seat

B.some of the seats were not occupied

C.there was a seat that he had hoped to have

D.the plane was not very crowded小题2:Which of the following is TRUE according to the passage?

A.Mr. Robinson was the last passenger to get on board the plane.

B.Mr. Robinson was surprised to see the notice in the seat.

C.The window seats were all occupied when Mr. Robinson got on hoard the plane.

D.The plane Mr. Robinson took was heavily loaded with luggage.小题3:In the end Mr. Robinson found out that _________.

A.the notice was put on the seat by the soldier.

B.the solider was waiting for his girl friend

C.the girl was the last passenger who got on the plane.

D.the seat by the window was kept for the last passenger.小题4:This short passage may be taken from a _____.

A.novel

B.news report

C.science fiction

D.magazine.

题型:问答题

两极格局解体后,政治经济趋向多极化,同时经济全球化和经济区域化趋势也日趋加强。下图是下列哪一组织的会标(  )

A.世界贸易组织

B.亚太经合组织

C.欧洲联盟

D.北美自由贸易区

题型:问答题

关于甲状腺髓样癌,下列论述错误的是()

A.甲状腺髓样癌起源于甲状腺滤泡上皮

B.髓样癌占甲状腺癌7%

C.甲状腺髓样癌的肿瘤标记物是降钙素

D.手术原则同 * * 状腺癌

E.可兼有淋巴和血行转移

题型:问答题

成年女性 * * 的主要构成包括()

A.皮肤、皮下脂肪及韧带

B.脂肪、腺叶及小叶

C.皮肤、皮下脂肪及腺体

D.皮肤、皮下脂肪及肌肉

E.腺叶、腺泡及脂肪

题型:问答题

澳门特别行政区设立的法院是()。

A.行政法院

B.区域法院

C.裁判署法庭

D.高等法院

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