题干

某工厂的酸性废水中含有大量的Fe3+、Cu2+、SO42和少量Na+.为了减少污染并变废为宝,工程师们设计了如下流程,回收铜和绿矾.

(1)工业废水中加入试剂A后,反应的离子方程式为Fe+Cu2+═Fe2++Cu、Fe+2H+═Fe2++H2↑、____  .

(2)试剂B是____ .

(3)①~③中均涉及的实验操作是____ .

(4)可用绿矾消除工业废水中+6价铬(Cr2O72)的污染,使之转化为Cr3+,若处理1t废水(含Cr2O72 103 mol/kg),则需加入绿矾的质量至少为 ____ g .

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答案(点此获取答案解析)

2Fe3++Fe═3Fe2+,H2SO4,过滤、蒸发浓缩、冷却结晶,1668

同类题3

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

    Food safety is a problem in all places around the world and people in different areas of the world prepare foods in different ways. The WHO released (发布) five simple rules for preparing food in a safe way. They call these rules the “Five Keys to Safer Food”.

Key 1: Keep clean

    ____People should wash their hands often — before touching food and while they are preparing food. People should wash all surfaces and equipment used for preparing food.

Key 2: Separate raw (生的) and cooked

    Raw foods should not touch prepared foods.____.

Key 3:____

    People should cook eggs and meat especially carefully. These foods may carry more micro-organisms (微生物) than other foods. Food like soup must be boiled for at least a minute to make it be cooked completely. It is also important that people re-heat cooked food completely.

Key 4: Keep food at safe temperatures

    When people finish eating, they should keep the left food in a refrigerator below 5℃and shouldn't store it for too long. At room temperature, about 20℃, the amount of micro-organisms can increase very quickly. But temperatures above 60℃ or below 5℃ control the growth of micro-organisms.____.

Key 5: Use safe water and raw materials

    ____. Damaged or old food may develop harmful chemicals as it gets older.

A. Cook completely

B. This key tells about the importance of washing

C. Eat healthily

D. They can live where we make food

E. People should use safe water and choose fresh foods

F. They cannot grow as quickly in a very hot or very cold environment

G. People should use separate equipment and tools for touching and preparing raw foods