处理含正六价铬的废水样液(+6价Cr的含量为78mg/L)。实验步骤如下

搜题请搜索小程序“爱下问搜题”

问题填空题

处理含正六价铬的废水样液(+6价Cr的含量为78mg/L)。实验步骤如下：

①取1L废水加入一定量1.8mol/LH₂SO₄溶液使样液酸化

②加入一定量的绿矾(FeSO₄·7H₂O)，将正六价铬转化为正三价铬离子

③加入过量的石灰水，使正三价铬离子转化为Cr(OH)₃沉淀

④过滤，除去沉淀物

(1)配制步骤①中所需H₂SO₄溶液100 mL，需用18 mol/L H₂SO₄溶液的体积是____ mL。

(2)步骤②中反应的离子方程式为14H⁺+Cr₂O₇^2-+6Fe²⁺==2Cr³⁺+6Fe³⁺+7H₂O此反应中氧化剂和还原剂物质的量之比为。

(3) 处理1L该废水样液至少需要绿矾 __ g。

答案

(1)10

(2)1：6

(3)1.25

问答题

The American economic system is organized around a basically private-enterprise, market-oriented economy in which consumers largely determine what shall be produced by spending their money in the marketplace for those goods and services that they want most. Private businessmen, striving to make profits, produce these goods and services in competition with other businessmen; and the profit motive, operating under competitive pressures, largely determines how these goods and services are produced. (47)Thus, in the American economic system it is the demand of individual consumers, coupled with the desire of businessmen to maximize profits and the desire of individuals to maximize their incomes that together determine what shall be produced and how resources are used to produce it.
(48)An important factor in a market-oriented economy is the mechanism by which consumer demands can be expressed and responded to by producers. In the American economy, this mechanism is provided by a price system, a process in which prices rise and fall in response to relative demands of consumers and supplies offered by seller-producers. If the product is in short supply relative to the demand, the price will be bid up and some consumers will be eliminated from the market. (49)If, on the other hand, producing more of a commodity results in reducing its cost, this will tend to increase the supply offered by seller-producers, which in turn will lower the price and permit more consumers to buy the product. Thus, price is the regulating mechanism in the American economic system.
The important factor in a private-enterprise economy is that individuals are allowed to own productive resources (private property), and they are permitted to hire labor, gain control over natural resources, and produce goods and services for sale at a profit. (50)In the American economy, the concept of private property embraces not only the ownership of productive resources but also certain rights, including the right to determine the price of a product or to make a free contract with another private individual.

查看答案

判断题

警民联防、警民共建精神文明，110报警服务监督系统，流动治安派出所等，开拓了人民警察与人民群众携手维护社会治安的新渠道。 ( )

查看答案