问题 填空题

现用质量分数为98%、密度为1.84g•cm3的浓H2SO4配制500mL、0.2mol•L-1的稀H2SO4.可供选择的仪器有:①玻璃棒 ②烧瓶 ③烧杯 ④胶头滴管 ⑤量筒 ⑥容量瓶 ⑦托盘天平 ⑧药匙.请回答下列问题:

(1)上述仪器中,在配制稀H2SO4时用不到的有______(填代号).

(2)经计算,需浓H2SO4的体积为______.现有①10mL  ②50mL  ③100mL三种规格的量筒,你选用的量筒是______

(3)将浓H2SO4加适量蒸馏水稀释后,冷却片刻,随后全部转移到______ mL的容量瓶中,转移时应用玻璃棒______.转移完毕,用少量蒸馏水洗涤______2~3次,并将洗涤液全部转移到容量瓶中,再加适量蒸馏水,振荡容量瓶,使溶液混合均匀.然后缓缓地把蒸馏水直接注入容量瓶直到液面接近刻度______处.改用______滴加蒸馏水到瓶颈刻度的地方,使溶液的______.振荡、摇匀后,装瓶、贴签.

(4)在配制过程中,其他操作都准确,下列操作中错误的是______(多选)

①洗涤量取浓H2SO4后的量筒,并将洗涤液转移到容量瓶中

②未等稀释后的H2SO4溶液冷却至室温就转移到容量瓶中

③将浓H2SO4直接倒入烧杯,再向烧杯中注入蒸馏水来稀释浓H2SO4

④定容时,加蒸馏水超过标线,又用胶头滴管吸出

⑤转移前,容量瓶中含有少量蒸馏水

⑥定容摇匀后,发现液面低于标线,又用胶头滴管加蒸馏水至标线

⑦定容时,俯视标线

⑧最后定容后,发现在刻度线的上方粘有一滴H2SO4的浓溶液.

答案

(1)配制步骤有量取、稀释、移液、洗涤、定容、摇匀等操作,一般用量筒量取(用到胶头滴管)称量,在烧杯中稀释,冷却后转移到500mL容量瓶中,并用玻璃棒引流,当加水至液面距离刻度线1~2cm时,改用胶头滴管滴加,所以需要的仪器为:玻璃棒、烧杯、胶头滴管、量筒、容量瓶,故答案为:②⑦⑧;

(2)设需要98%H2SO4的体积为VmL,根据溶液稀释前后溶质质量不变则,VmL×1.84g/cm3×98%=500mL×0.2mol•L-1×98g/mol,解得V=5.4ml,选用量筒的规格为10mL,

故答案为:5.4ml;10mL;

(3)配制步骤有量取、稀释、移液、洗涤、定容、摇匀等操作,一般用量筒量取(用到胶头滴管)称量,在烧杯中稀释,冷却后转移到500mL容量瓶中,并用玻璃棒引流,转移完毕,用少量蒸馏水洗涤烧杯及玻璃棒2~3次并将洗涤液全部转移到容量瓶中,再加适量蒸馏水,当加水至液面距离刻度线1~2cm时,改用胶头滴管滴加,使溶液的凹液面的最低点与刻线相平,故答案为:500;引流;烧杯及玻璃棒;1-2cm;胶头滴管;凹液面的最低点与刻线相平;

(4)①洗涤量取浓H2SO4后的量筒,不需要将洗涤液转移到容量瓶中,故①错误;

②稀释后的H2SO4溶液应冷却至室温才能转移到容量瓶,故②错误;

③稀释浓H2SO4时,将浓H2SO4沿着烧杯内壁缓慢倒入盛有蒸馏水的烧杯中,故③错误;

④定容时,加蒸馏水超过标线,不能胶头滴管吸出,应重新配制,故④错误;

⑤转移前,容量瓶中含有少量蒸馏水,对实验无影响,故⑤正确;

⑥定容摇匀后,发现液面低于标线,又用胶头滴管加蒸馏水至标线,这样会导致溶液的体积偏大,故⑥错误;

⑦定容时,俯视标线,会使溶液的体积偏小,故⑦错误;

⑧最后定容后,发现在刻度线的上方粘有一滴H2SO4的浓溶液,这样会导致溶液的体积偏大,故⑧错误;

故答案为:①②③④⑥⑦⑧.

阅读理解

A student was one day taking a walk with his teacher. As they went along, they saw a pair of old shoes lying in the path. They were a poor farmer’s, who was working in the nearby field.

The student turned to the teacher, saying:“we will hide his shoes, and hide ourselves behind those trees, and wait to see what he will do”

“My young friend,” answered the teacher, “we should never make fun of the poor. Why not put a coin in each shoe, and then we will hide ourselves and watch?”  The student did so and they both hid themselves behind the trees. The poor man soon finished his work, and came across the field to the path where he had left his coat and shoes.

After putting on his coat, he put his foot into one of his shoes, and felt something hard. Then he bent down to feel what it was, and found the coin. Surprised, he looked at the coin, turned it around and looked at it again. He then looked around, but no person was seen. He put the money into his pocket, and continued to put on the other shoe. His surprise was doubled on finding the other coin.

He couldn’t control his feelings and fell to his knees, looked up to the sky and expressed his thanks. Then he spoke of his wife, sick and helpless, and his children without food. He said the help would save them from dying.

The student there deeply moved, and his eyes filled tears.“ Now,” said the teacher, “are you not much happier than if you had hidden the shoes?”

小题1:When the student saw the shoes, he wanted to____.

A.steal them

B.find their owner

C.play a joke on the owner

D.give the owner some money小题2:According to the passage, the teacher is______.

A.quiet and honest

B.kind and friendly

C.patient and clever

D.strict and careful小题3:When the farmer saw the second coin, he___.

A.was very excited and grateful

B.was worried and looked up at the sky

C.was surprised and decided to find the owner

D.spoke of his difficulties and asked for more help小题4:At the end of the story, the student____.

A.was very proud of himself

B.was very pleased with his life

C.felt very sorry about his first idea

D.felt sad for not taking his teacher’s advice

单项选择题