11.9 双重替换反应

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  双重替换

  

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  Want to trade?
  ::想交换吗?

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  The practice of barter (trading one thing for another) has been in existence for a very long  time. In the illustration above, items like chickens were bartered for newspapers. You have something I want, and I have something you want. So we trade and we each have something new. Some are like that. Compounds swap parts and you have new materials.
  ::易货交易(以一物换另一物)的做法已经存在了很长一段时间。在上文的插图中,鸡等项目被以报纸换了。你有我想要的东西,我也有你想要的东西。所以我们交易,我们每个人都有新的东西。有些就是这样。化合物交换部件,你也有新的材料。

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  Double-Replacement Reactions
  ::双重替换

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  A double- is a reaction in which the positive and negative of two exchange places to form two new compounds. The general form of a double-replacement (also called double-displacement) reaction is:
  ::一种双重反应,即两个交换点的正负成两个新的化合物。

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  $$\begin{array}{r}AB+CD\to AD+CB\end{array}$$

  
  ::AB+CD=AD+CB +CD=AD+CB +CD=AD+CB+AD+AD+CB+AB+AD+AD+CB+AB+AD+AD+CB+AD+AD+CB+AD+AD+AD+AD+CB+AD+AD+CB+AD+AD+AD+AD+CB+AD+AD+CB+AD+AD+AD+AD+AD+CB+AD+CB+AD+AD+AD+CB+AD+AD+AD+AD+CB+CB+AD+ADD+CD+CB+AD+AD+CDD+CDDDD+C+CDDAD+CDDAD+AD+ADD+C+C+C+CDDAD+C+C+CDDDDDDDDD+CDDDDD+CD+C+C+C+CDDDADDD+C+C+CDDDDDDDD+C+C+C+C+C+CDD+C+C+C+C+C+C+C+C+CDDD+C+C+C+CD+C+C+CD+CDDDDDDDDDDDDDDDDDDDDDD+C+C+C+C+C+C+CDDDDD+C+C+C+C+C+CD+C+C+CD+C+C+C+C+C+C+C+C+C+C+CDD+C+CDDD+CDDDDDDDDDDDDDDDD+CDDDDDDDDDDDDDDDDDDDDDDDD+CDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD

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  In this reaction,  $\begin{array}{r}A\end{array}$ and  $\begin{array}{r}C\end{array}$ are positively-charged , while  $\begin{array}{r}B\end{array}$ and  $\begin{array}{r}D\end{array}$ are negatively-charged . Double-replacement reactions generally occur between substances in aqueous solution . In order for a reaction to occur, one of the products is usually a solid precipitate , a , or a molecular such as water.
  ::在这种反应中,A和C是积极的,而B和D是负的。 水溶物中的物质之间通常会发生双重替代反应。 为了发生反应,产品之一通常是固体加速剂、一个或一个分子,如水。

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  Formation of a Precipitate
  ::降水层形成

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  A precipitate forms in a double-replacement reaction when the cations from one of the reactants combine with the anions from the other reactant to form an insoluble ionic compound. When aqueous solutions of potassium iodide and lead(II) nitrate are mixed, the following reaction occurs.
  ::当反应剂之一的电反应剂与另一反应剂的阴离子结合,形成不可溶解的离子化合物时,即产生双重替代反应,当碘化钾和硝酸铅(II)硝酸铅的水溶液混合时,即发生下列反应。

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  $$\begin{array}{r}2\text{KI}(aq)+{\text{Pb(NO}}_3{)}_2(aq)\to 2{\text{KNO}}_3(aq)+{\text{PbI}}_2(s)\end{array}$$

  
  ::2 KI(aq)+Pb(NO3)(2)(aq)+Pb(2)(a)+KNO3(a)+PbI2(s)

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  There are very strong attractive forces that occur between Pb ²⁺ and I ⁻ ions and the result is a brilliant yellow precipitate (see Figure ). The other product of the reaction, potassium nitrate, remains soluble.
  ::Pb2+和I-离子之间有非常强大的有吸引力的力量,其结果是一种光辉的黄(见图),反应的另一个产物硝酸钾仍然可以溶解。

  

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  Formation of lead iodide precipitate.
  ::形成含铅碘化催化剂。

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  Formation of a Gas
  ::气体的形成

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  Some double-replacement reactions produce a gaseous product which then bubbles out of the solution and escapes into the air. When solutions of sodium sulfide and hydrochloric are mixed, the products of the reaction are aqueous sodium chloride and hydrogen sulfide gas.
  ::有些双重替代反应产生气体产品,然后从溶液中冒出来,并渗入空气中。 当硫化钠和盐酸钠的溶液混杂在一起时,反应的产品是水氯化钠和硫化氢气体。

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  $$\begin{array}{r}{\text{Na}}_2\text{S}(aq)+2\text{HCl}(aq)\to 2\text{NaCl}(aq)+{\text{H}}_2\text{S}(g)\end{array}$$

  
  ::Na2S(aq)+2HCl(aq)+2Na2NaCl(aq)+H2S(g)

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  Formation of a Molecular Compound
  ::分子化合物的形成

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  Another kind of double-replacement reaction is one that produces a molecular compound as one of its products. Many examples in this category are reactions that produce water. When aqueous hydrochloric acid is reacted with aqueous sodium hydroxide, the products are aqueous sodium chloride and water.
  ::另一种双重替代反应是生产一种分子化合物作为产品之一。这类反应中有许多例子是产生水的反应。当水氯化盐酸与水氧化钠发生反应时,这些产品是水氯化钠和水。

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  $$\begin{array}{r}\text{HCl}(aq)+\text{NaOH}(aq)\to \text{NaCl}(aq)+{\text{H}}_2\text{O}(l)\end{array}$$

  
  ::HCl(aq) + NaOH(aq) + NaCl(aq)+H2O(l)

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  Sample Problem: Double-Replacement Reactions
  ::问题:双重替换反应

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  Write a complete and balanced chemical equation for the following double-replacement reactions. One product is indicated as a guide.
  ::为以下的双重替换反应写出完整和平衡的化学方程式。一个产品被标为指南。

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  A.  $\begin{array}{r}\text{NaCN}(aq)+\text{HBr}(aq)\to \end{array}$ (hydrogen cyanide gas is formed)
  ::a. NaCN(aq)+HBr(aq) (形成氰化氢气)

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  B.  $\begin{array}{r}({\text{NH}}_4{)}_2{\text{SO}}_4(aq)+{\text{Ba(NO}}_3{)}_2(aq)\to \end{array}$ (a precipitate of barium sulfate forms)
  ::B. (NH4)2SO4(aq)+Ba(NO3)(2(aq) +(硫酸铵形式的催化物)

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  Step 1: Plan the problem.
  ::第1步:规划问题。

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  In A, the production of a gas drives the reaction. In B, the production of a precipitate drives the reaction. In both cases, use the ionic charges of both reactants to construct the correct formulas of the products.
  ::在A类中,气体的生产会推动反应,在B类中,加速剂的生产会推动反应,在这两种情况下,使用两个反应器的电离电荷来构建正确的产品配方。

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  Step 2: Solve.
  ::步骤2:解决。

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  A. The cations of both reactants are +1 charged ions, while the anions are -1 charged ions. After exchanging partners, the balanced equation is:
  ::A. 两个反应器的电离子的电离子为+1充电离子,而阴离子为-1充电离子。

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  $$\begin{array}{r}\text{NaCN}(aq)+\text{HBr}(aq)\to \text{NaBr}(aq)+\text{HCN}(g)\end{array}$$

  
  ::NaCN(aq)+HBR(aq)+Nabr(aq)+HCN(g)

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  B. Ammonium ion and nitrate ion are 1+ and 1− respectively, while barium and sulfate are 2+ and 2−. This must be taken into account when exchanging partners and writing the new formulas. Then, the equation is balanced.
  ::B. 离子和硝酸盐离子分别为1+和1-,和硫酸盐分别为2+和2-,在交换伙伴和编写新公式时必须考虑到这一点。

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  $$\begin{array}{r}({\text{NH}}_4{)}_2{\text{SO}}_4(aq)+{\text{Ba(NO}}_3{)}_2(aq)\to 2{\text{NH}}_4{\text{NO}}_3(aq)+{\text{BaSO}}_4(s)\end{array}$$

  
  :NH4)2SO4(q)+Ba(NO3)2(q)2NH4NO3(q)+BaSO4(s)

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  Step 3: Think about your result.
  ::步骤3:想想你的结果。

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  Both are double-replacement reactions. All formulas are correct and the equations are balanced. Occasionally, a reaction will produce both a gas and a molecular compound. The reaction of a sodium carbonate solution with hydrochloric acid produces aqueous sodium chloride, carbon dioxide gas, and water.
  ::这两种反应都是双重替代反应。 所有公式都正确,方程式也平衡。 偶尔,一种反应会产生一种气体和一种分子化合物。 碳酸钠溶液与盐酸的反应会产生水氯化钠、二氧化碳气体和水。

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  $$\begin{array}{r}{\text{Na}}_2{\text{CO}}_3(aq)+2\text{HCl}(aq)\to 2\text{NaCl}(aq)+{\text{CO}}_2(g)+{\text{H}}_2\text{O}(l)\end{array}$$

  
  ::Na2CO3(aq)+2HCl(aq)+2NaCl(aq)+CO2(g)+H2O(l)

   

   

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  Summary
  ::摘要

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  • The double-replacement reaction generally takes the form of AB + CD → AD + CB where  A and C are positively-charged cations, while B and D are negatively-charged anions.
    ::双重替换反应一般采取AB+CD AD+CB的形式,A和C是正电荷的电弧,B和D是负电荷阴离子。
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  • In a double replacement reactions ,  typically one of the products is a precipitate, a gas, or a molecular compound.
    ::在一种双重替代反应中,通常一种产品是沉淀物、一种气体或一种分子化合物。

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  Review
  ::回顾

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  1. In a double-replacement reaction, what type of compounds are usually the reactants? A double-replacement reaction occurs between sodium sulfide and hydrogen chloride. Write the rest of the chemical equation and balance it.
     ::在双重替代反应中,哪种化合物通常是反应剂?在硫化钠和氯化氢之间发生双重替代反应。化学方程的其余部分写成并平衡。
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  2. Na ₂ S + HCl →
     ::Na2S + HCl +
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  3. In double-replacement reaction,  one of  three possible types of products usually form. What are the three types?
     ::在双重替代反应中,三种可能的产品通常形成三种类型的产品之一,这三种类型是什么?