试题与答案

使用浓硫酸时要十分小心,浓硫酸有强烈的!所以,不要将浓硫酸沾到皮肤或衣服上。为了

题型:填空题

题目:

使用浓硫酸时要十分小心,浓硫酸有强烈的         !所以,不要将浓硫酸沾到皮肤或衣服上。为了加深记忆,小丽同学用下图形象地总结了硫酸能与5类物质发生反应。请你根据要求完成下列问题。

(1)将紫色石蕊溶液滴入稀硫酸溶液中,紫色石蕊溶液遇稀硫酸变成                                          

(2)稀硫酸能够除铁锈(铁锈的主要成分Fe2O3),除锈后溶液颜色的变化情况是                                

写出反应的化学方程式                            

(3)为了验证反应⑤能够发生,应选择的物质是               

A.NaCl溶液

B.NaOH溶液

C.Ba(NO3 )2溶液

D.MgCl2溶液(4)用废铁屑与废硫酸(H2SO4的质量分数为20%)反应可制取硫酸亚铁,写出由废铁屑中铁制取硫酸亚铁的化学反应方程式          ;若得到的硫酸亚铁溶液中含少量硫酸铜,请你选择合适的物质除去硫酸铜,写出其化学反应方程式                      

答案:

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Insurance is the sharing of (1) . Nearly everyone is exposed (2) risk of some sort. The house owner, for example, knows that his (3) can be damaged by fire; the ship owner knows that his vessel may be lost at sea; the breadwinner knows that he may die by (4) and (5) his family in poverty. On the other hand, not every house is damaged by fire or every vessel lost at sea. If these persons each put a (6) stun of money into a pool, there will be enough to (7) the needs of the few who do suffer (8) . In other words the losses of the few are met from the contributions of the (9) . This is the basis of (10) . Those who pay the contributions are known as (11) and those who administer the pool of the contributions as insurer.
The (12) for an insurance naturally depends on how the risk is to happen as suggested (13) past experience. If the companies fix their premiums too (14) , there will be more competition in their branch of insurance and they may lose (15) . On the other hand, if they make the premiums too low, they will not have (16) and may even have to drop out (17) business. So the ordinary forces of supply and (18) keep premiums at a proper (19) to both insurers and those who (20) insurance.

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