写出下列反应的化学方程式．
（1）细铁丝在氧气中燃烧______；
（2）硫在空气中燃烧生成二氧化硫______；
（3）一氧化碳燃烧生成二氧化碳______；
（4）电解水生成氢气和氧气______．
（1）铁丝在氧气中燃烧的反应物是铁和氧气，生成物是四氧化三铁，反应条件是点燃，用最小公倍数法配平，所以方程式是：3Fe+2O2
Fe3O4； 点燃 .
（2）硫和氧气在点燃的条件下生成二氧化硫，故答案为：S+O2
SO2； 点燃 .
（3）一氧化碳在氧气中燃烧会生成二氧化碳，故答案为：2CO+O2
2CO2； 点燃 .
（4）水通电分解会生成氧气和氢气，故答案为：2H2O
2H2↑+O2↑；通电 . .
故答案为：（1）3Fe+2O2
Fe3O4（2）S+O2 点燃 .
SO2；（3）2CO+O2 点燃 .
2CO2（4）2H2O 点燃 .
2H2↑+O2↑；通电 . .
| Questions 84-90 are based on the following passage. Imagine a society in which cash no longer exists. Instead "cash" is electronic, as in bankcard systems. Currency and coin are abandoned. The immediate benefits would be profound and fundamental. Theft of cash would become impossible. Bank robberies and cash-register robberies would simply cease to occur. Attacks on shopkeepers, taxi drivers, and cashiers would all end. Purse snatchings would become a thing of the past. Urban streets would become safer. Retail shops in once-dangerous areas could operate in safety. Security costs and insurance rates would fall. Property values would rise. Neighborhoods would improve. Drug traffickers and their clients, burglars and receivers of stolen property, arsonists for hire, and bribe-takers would no longer have the advantage of using untraceable currency. Electronic "money" would leave incriminating wails of data, resulting in more arrests and convictions. These prosecutions, in turn, would inhibit further crimes. The impact of the monetary change on underground economies would be nearly as dramatic as the effect on crime. In the United States, the underground economy is estimated at between 10% and 28% of the gross national product. Internal Revenue Service (IRS) researches suggest that almost all hidden labor is paid in currency. In a society devoid of physical money, a change from cash to recorded electronic money would be accompanied by a flow of previously unpaid income-tax revenues running in the tens of billions of dollars. As a result, income-tax rates could be lowered and the national debt reduced. Cash has been the root of much social and economic evil. The emergence of electronic funds-transfer technology makes it possible to change the nature of money and to divorce it from evil. Eighty percent of Americans regularly use credit cards. The development of a federal system to handle the country’ s 300 billion annual cash transactions in the United States electronically is within reach. A national electronic-money system would operate as debit-card system. Each individual’s "money" would be held in his money-system account. A transaction would effect an instant transfer of "money" from his account to that of another account holder. The principal differences between a national electronic-money system and commercial bank-card systems would be: the money system would be federally operated; payment would constitute "legal tender"; system-account holders would be able to receive as well as pay out funds by use of their accounts; and funds would be transferable between private-account holders as well as between merchants and private-account holders. Only cash would be supplanted by electronic money. The use of checks, drafts, money orders, traveler’s checks, cashier’s checks, as well as letters of credit, acceptances, and other financial instruments would remain in regular use. Credit card and automatic-teller-machine systems (ATMs) would not necessarily change, although you could no longer obtain cash at ATMs. |
"Hidden labor" in this passage refers to labor that is paid in ______.
A．electronic money
B．money that is hard to count
C．after-tax money
D．money that is untaxed