问题 计算题

为了测定某氢氧化钠固体是否含有碳酸钠(不含其他杂质),现用纯氢氧化钠与其对比进行对比实验如下:

①称取纯氢氧化钠和待测氢氧化钠各mg分别配成25.0g溶液,均滴加酚酞2~3滴.

②把12.0%的盐酸逐滴加入实验①配成的两种溶液中,当酚酞试液刚好由红色变为无色(溶液呈中性)时,纯氢氧化钠配成的溶液消耗盐酸n1g,待测氢氧化钠配成的溶液消耗盐酸n2g.

(1)若m=2.73g,n1=n2=20.8g,则待测氢氧化钠配成的溶液中NaOH 的质量分数是多少?(2)若m=2.73g,n1=20.8g,n2=19.7g,则待测氢氧化钠配成的溶液中NaOH 的质量分数是多少?

答案

(1)n1=n2时,不含Na2CO3,则有 ×100%=10.9%

(2)n1>n2时,含Na2CO3,8.64%

阅读理解

阅读理解。

     When I was 13 years old, I became a vegetarian and quickly realized that I would have to learn how

to cook for myself. The first thing I ever asked my mom to teach me how to make was bean soup."Oh,

that's easy!" She told me. She started by explaining: "Almost every soup starts with onions and carrots."

     My mom is a chef who is able to cook delicious meals. She also told me that the very first thing she

had learned in cooking school was to make soup stock (拼盘)----followed by soup. Her teacher had told

the class: "If you learn anything here, it should be soup."

    In the US, soup isn't so much a part of a meal as a meal in itself. Soups are often made from the

leftovers (剩菜) of last night's dinner----a baked chicken or turkey can easily be made into a new meal by

adding broth (肉汤) and some vegetables. Soups are accompanied (伴随) by bread and topped with cheese.

    It was easy to impress my college roommates with my mom's great soup recipes (菜谱). Bean soup,

vegetable noodle soup, mushroom soup… For only a few dollars, three or four of us could eat well from

the same pot of soup for a whole week. Add a loaf of bread and some cheese, and our soup became a proper

feast (盛宴).

    I'm not a vegetarian any more, but I still make bean soup. It fills the house with lovely smells and reminds

me of my mom, and my home.

1. The first thing that the writer learnt to make was _______.

A. bean soup

B. vegetable noodle soup

C. mushroom soup

D. beef soup

2. What is the writer's mother's job?

A. teacher

B. officer

C. chef

D. secretary

3. According to the writer's mother, almost every soup has _______.

A. onions and carrots

B. celery (芹菜) and chili (辣椒)

C. carrots and mushroom

D. bread and cheese

4. Which of the statements is TRUE?

A. Soup is as important as a meal in America.

B. Americans don't like to make soup from leftovers.

C. Americans think it is difficult to make soup.

D. Americans like to add cheese to soup.

5. From this passage, we can learn that _______.

A. in the US, soup isn't part of every meal

B. you can't make soup with a baked chicken or turkey

C. the writer often made different kinds of soup at home with her roommates

D. the writer doesn't make bean soup any more because she isn't a vegetarian

单项选择题 A1/A2型题