下列化学式能真实表示物质分子组成的是（ ）
A．NaOH
B．SO3
C．CsCl
D．SiO2
答案：B
题目分析：能用化学式表示物质分子组成的必须是分子晶体，由分子组成，NaOH是离子晶体，有阴、阳离子构成； SO3是分子晶体，由分子组成；CsCl是离子晶体； SiO2是原子晶体，是由原子组成的。
点评：本题考查晶体类型的判断，题目难度不大，注意只有分子晶体才含有单个分子，化学式即分子式。
Oil is so important that it is sometimes called “black gold”. Almost half our energy from oil. We use it to run our cars and factories and to our homes, offices and schools. Many everyday things are made from oil. Your shirt may have oil in the material(材料). The soap you your hands with might also be made from oil. Children’s plastic toys are made from oil. Oil is to find, because it is deep under the earth. Today, however, we have many to find oil. One tool measures(测量) the pull of gravity(重力). Places where gravity is weaker are more likely to have oil. tool measures sound waves. Sound waves travel different kinds of rocks at different speeds. We can use to find the rocks that have oil in them. We need oil, and we are using up the oil wells(井) we know about. we must find new ways of looking for this “black gold”. Can you do anything for it?
|