问题 问答题

味精是我们家庭厨房常见的一种调味品,它是一种化合物--谷氨酸钠,其化学式为C5H8NO4Na.下表为家庭常见食品中味精的含量,根据题中的信息计算:

食品名称500g食品的味精含量/mg
普通炒菜400
炖排骨240
水饺130
(1)谷氨酸钠由______种元素组成的,相对分子质量是______.

(2)谷氨酸钠中氮、氢元素的质量比为______;其中在谷氨酸钠中______元素含量最高.

(3)若小明同学一次吃了400g水饺,则他食用______mg味精,其中含钠元素的质量为______mg(结果保留一位小数).

答案

(1)由谷氨酸钠的化学式可知,谷氨酸钠是由碳、氢、氮、氧、钠五种元素组成的;相对分子质量为12×5+1×8+14+16×4+23=169.

(2)谷氨酸钠中氮、氢元素的质量比为14:(1×8)=7:4.

谷氨酸钠中碳原子的相对原子质量之和为12×5=60,氢原子的相对原子质量之和为1×8=8,氮原子的相对原子质量之和为14,氧原子的相对原子质量之和为16×4=64,钠原子的相对原子质量之和为23,氧元素的相对原子质量之和最大,则氧元素的质量分数最高.

(3)根据题意,500g水饺的味精含量130mg,则400g水饺中含有味精的质量为130mg×

400
500
=104mg;其中含钠元素的质量为104mg×
23
169
×
100%≈14.2mg.

故答案为:(1)5;169;(2)7:4;氧;(3)104;14.2.

阅读理解

    Mr. Brown lived in a house less than two miles from his office, so he was able to drive home every day for lunch. Every time he drove home at noon, he found many cars were parked outside his house and there was no room for his own car. He had to drive somewhere else to park his car. Then he had to walk back home. This made him very angry.

He had put up a board, which said, “ No parking” in the garden facing the road, but nobody noticed it. People seemed to obey(遵守) only a police notice with letters on a blue board:

POLICE NOTICE

NO PARKING

Mrs. Brown suggested that he could steal a police notice. He was afraid to do so. She then suggested that he could make one just like a police notice. He said he was not the police and couldn’t use the word “police”. Several days later, Mr. Brown made a blue board with white letters:

POLITE NOTICE

NO PARKING

“ Oh!” Mrs. Brown said, “You told me you weren’t going to use the word  “police”, but why do you use it now?” “Really?” he asked, “Look again.” She started to laugh. “You are really clever.”

小题1:How many notice boards did Mr. Brown make altogether?

A.Only one

B.Two

C.Three

D.None小题2:Mr. Brown made a notice board which ________________ in the end.

A.was just the same as a police notice

B.was different in colour from a police notice

C.looked just like a police notice

D.said “ POLICE NOTICE, NO PARKING”小题3:We can infer(推断) that ____________ after he put up the blue board.

A.more people will park their cars outside his house

B.more policemen will come to park their cars at noon

C.fewer people will visit him at noon later on

D.fewer people will park their cars outside his house

多项选择题