钠、镁、铝分别与足量稀硫酸反应，生成等质量氢气时，参加反应的_爱下问搜题

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问题选择题

钠、镁、铝分别与足量稀硫酸反应，生成等质量氢气时，参加反应的钠、镁、铝的原子数目之比是（　　）

A．1：2：3

B．3：2：1

C．6：3：2

D．4：2：1

答案

根据金属的质量×

金属元素的化合价

金属的相对原子质量

=生成氢气的质量，设钠、镁、铝的质量分别为X、Y、Z则：X×

1

23

=Y×

1

12

=Z×

1

9

，可得X：Y：Z=23：12：9，所以钠、镁、铝的原子数目之比为：

23

23

：

12

24

：

9

27

=6：3：2．

故选C．

完形填空

完形填空。

                                          How 3D Movies Work   .
     Do you know 3D movies? When you see one, it's like the story  l in front of you, and you are a part ofit. 3D movies are exciting to   2   , but do you
know how3      them, and     4   you need to wear a pair of 3D glasses? To
understand these questions, let's make an easy   5  .
     O Put a finger   6   your eyes.
     O Cover your lef't eye and look at the finger.
     O Cover your right eye and look at the finger.
     What do you see:l The finger you see with your left eye is in a different
position from the one you see with your right eye. This means you get two
images(图像) when you look at   7     _ with both your eyes. To makea 3D
movie, people have to get two images at the same time,   8_ they use two
video cameras.  When playing a 3D movie, they use two projectors (放机)
at the same time.  This brings two images together on the screen. Then, we
use 3D glasses to separate(识别) the two images. One image enters one eye
and   9 enters the other eye.
     Then our brains   10     the two images together. In this way, we get 3D
pictures.

( )1. A. happen
( )2. A. watch
( )3. A. make
( )4. A. when
( )5. A. examl)le
( )6. A. in front of
( )7. A. everything
( )8. A. because
( )9. A. other
( )10.A. let

B. happened
B. see
B. to make
B. why
B, picture
B. in the front of
B. anything
B. so
B. the other
B. put

C. to happen
C. look
C. making
C. which
C. experiment
C. behind
C. something
C. and
C. others
C. take

D. happening
D. notice
D. made
D. what .
D. mowe
D. beside
D. nothing
D. but
D. the others
D. bring

填空题

目前细纱机常用的加压形式有（）加压和（）加压。