问题 填空题

小明要到农资公司买8Kg的化肥硝酸铵______,其中有效成分为氮元素,但是当时没有硝酸铵了,如果要是改为购买尿素______,要想氮元素质量相等,则需要购买尿素______Kg.

答案

尿素[CO(NH22]的相对分子质量是12+16+(14+2)×2=60;

硝酸铵[NH4NO3]分子的相对质量为14+4+14+16×3=80;

8kg尿素中含氮元素的质量为:8kg×(

2×14
80
×100%)=2.8kg;

设需要购买尿素的质量为x,则x•(

2×14
60
×100%)=2.8kg;

解之得:x=6Kg.

故答案为:6.

阅读理解

阅读短文,选择正确答案。

       Here are some tips (建议) on how to stay safe in earthquakes (地震).

      1. Stay inside and duck and cover. Get under a desk or table, or stand in a corner or under a doorway.

Cover your head and neck with your arms.

      2. Move against a wall if in a high building with no protective desk or table nearby. Cover your head and

neck with your arms. 

      3. Try to get into an open area away from trees, buildings, walls, and power lines (电杆) if outdoors. 

      4. Pull over (停靠) to the side of the road away from overpasses (天桥) and power lines if driving. Stay in

your car until the shaking ends.

      5. Get away from shelves or other areas where objects may fall if in a crowded store or public area. Do

not run for the door. Lower your body close to the ground and cover your head and neck with your hands and

arms.

      6. Stay in your seat if in a cinema or a theater. Get below the level of the back of the seat and cover your

head and neck with your arms. 

      7. If you take cover (躲避) under a strong piece of furniture,hold on to it and be prepared to move with

it. 

      8. Try to stay away from kitchens, where there are often many objects that might fall or get burnt.

1. The underlined word "duck" in Tip 1 means            . [ ]

A. a water bird with short legs

B. some kind of meat for eating

C. walk like a duck

D. lower your head or body very quickly

2. _______ should be the most important part(s) to be protected in an earthquake. [ ]

A. Your head and arms

B. Your arms

C. Your neck and arms

D. Your head and neck

3. Tip3 and Tip4 give you some advice on what you should do when you are            . [ ]

A. inside a building

B. outside a building

C. in your house

D. in a store

解答题