问题 计算题

取50.0mL Na2CO3和Na2SO4的混合溶液,加入过量BaCl2溶液后得到14.51g白色沉淀,用过量稀硝酸处理后沉淀质量减少到4.66g,并有气体放出。试计算原混合液中Na2CO3和Na2SO4的物质的量浓度以及产生的气体在标准状况下的体积。

答案

c(Na2SO4)==0.40mol/L;

c(Na2CO3)==1.0mol/L。在标准状况下生成1.12L CO2

题中反应关系:BaCl2+Na2CO3=BaCO3↓+2NaCl

 BaCl2+Na2SO4=BaSO4↓+2NaCl

 BaCO3+2HNO3=Ba(NO3)2+H2O+CO2↑,知剩余白色固体为BaSO4

14.51g白色沉淀为BaSO4和BaCO3的混合物,其中不溶于稀硝酸的是4.66g BaSO4,则BaCO3质量为:

 14.51g-4.66g=9.85g。

 c(Na2SO4)==0.40mol/L;

 c(Na2CO3)==1.0mol/L。

设生成标准状况下的CO2气体体积为xL。

 BaCO3+2HNO3=Ba(NO3)2+CO2↑+H2O

 1mol        22.4L

 9.85/197mol     xL

x=1.12,即在标准状况下生成1.12L CO2

阅读理解

When you are learning English, you find it not clever to put an English sentence, word for word, into your own language. Take the sentence “How do you do?” as an example. If you look up each word in the dictionary, one at a time, what is your translation? It must be a wrong sentence in your own language.

Languages do not just have different sounds, they are different in many ways. It’s important to master(掌握) the rules for word order in the study of English, too. If the speaker puts words in a wrong order, the listener can’t understand the speaker’s sentence easily. Sometimes when the order of words in an English sentence is changed, the meaning of the sentence changes, But sometimes the order is changed, the meaning of the sentence doesn’t change. Let’s see the difference between the two pairs of sentences.

“She only likes apples.”               “Only she likes apples.”

“I have seen the film already.”           “I have already seen the film.”

When you are learning English, you must do your best to get the spirit(精神实质) of the language and use it as the English speaker does.

小题1:From the passage we know that _______when we are learning English.

A.we shouldn’t put every word into our own language

B.we should look up every word in the dictionary

C.we need to put every word into our own language

D.we must read word by word小题2:The writer thinks it is _______ in learning English.

A.difficult to understand different sounds

B.necessary to remember the word order

C.important to master the rules in different ways

D.easy to master the rules for word order小题3:We can learn from the passage that ________.

A.the meaning of an English sentence always changes with the order of the words

B.The order of words can never change the meaning of an English sentence

C.sometimes different order of words has a different meaning

D.if the order of words is different, the meaning of the sentence must be different小题4:“She only likes apples.” ________.

A.is the same as “Only she likes apples.”

B.is different from “Only she likes apples.”

C.means “She likes fruit except apples.”

D.means “She doesn’t like apples.”

单项选择题