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  • General

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  • 平衡化学等量

    A boy and girl on a seesaw; the boy's side is down, indicating unequal weights.

    The little boy on this seesaw weighs more than the little girl on the other side. That’s why his side of the seesaw is on the ground and her side is up in the air. For a seesaw to balance, the two riders must be the same . A chemical equation that represents a is a little bit like a seesaw. For a chemical equation to balance, there must be the same number of each type of on both sides of the equation.
    ::这个锯子上的小男孩比另一边的小女孩体重要高。 这就是为什么他那一边的锯子在地面,而她那一边在空中。 要平衡锯子,两个骑手必须是相同的。 代表一个的化学方程式有点像锯子。 要平衡一个化学方程式,方程式两侧的化学方程式数量必须相同。

    Writing Chemical Equations
    ::化学等式

    A chemical equation represents the changes that occur during a chemical reaction. A chemical equation has the general form:
    ::化学方程式代表化学反应期间发生的变化。化学方程式具有一般形式:

    Reactants → Products

    An example of a simple chemical reaction is the reaction in which hydrogen (H 2 ) and oxygen (O 2 ) combine to produce water (H 2 O). In this reaction, the reactants are hydrogen and oxygen and the product is water. To write the chemical equation for this reaction, you would start by writing the reactants on the left and the product on the right, with an arrow between them to show the direction in which the reaction occurs:
    ::简单的化学反应的一个例子是氢(H2)和氧(O2)结合产生水(H2O)的反应。在这种反应中,反应器是氢和氧,产品是水。写化学方程式来进行这种反应,首先写出左边的反应器和右边的产品,用箭来显示反应发生的方向:

    Equation 1:
    ::等式 1 :

    H 2 + O 2 → H 2 O
    ::H2 + O2 + H2O

    Q: Look closely at equation 1. There’s something wrong with it. Do you see what it is?
    ::问题:仔细看看方程1。它有问题。你看到它是什么吗?

    A: All chemical equations must be balanced. This means that there must be the same number of each type of atom on both sides of the arrow. That’s because mass is always conserved in chemical reactions. Count the number of hydrogen and oxygen atoms on each side of the arrow. There are two hydrogen atoms in both . There are two oxygen atoms in the reactants but only one in the product. Therefore, equation 1 is not balanced.
    ::A: 所有化学方程式都必须平衡。 这意味着箭头两侧的原子数量必须相同。 这是因为质量总是在化学反应中得到保护。 计算箭头两侧的氢和氧原子数量。 两者中都有两个氢原子。 反应器中有两个氧原子, 但产品中只有一个。 因此, 等式 1 并不平衡 。

    Using Coefficients
    ::使用系数

    Coefficients are used to balance chemical equations. A coefficient is a number placed in front of a chemical symbol or formula. It shows how many atoms or molecules of the substance are involved in the reaction. For example, two molecules of hydrogen would be written as 2 H 2 , and two molecules of water would be written 2 H 2 O. A coefficient of 1 usually isn’t written. Coefficients can be used to balance equation 1 (above) as follows:
    ::系数用于平衡化学方程式。系数是放在化学符号或公式前面的一个数字。它显示该物质的原子或分子在反应中涉及多少个原子或分子。例如,氢的两个分子将写成2H2,水的两个分子将写成2H2。系数通常不是写成的。系数1通常不是写成的。系数可以用来平衡公式1(以上)如下:

    Equation 2:
    ::等式 2 :

    2 H 2 + O 2 → 2 H 2 O
    ::2 H2 + O2 + 2 H2O

    Equation 2 shows that two molecules of hydrogen react with one molecule of oxygen to produce two molecules of water. The two molecules of hydrogen each contain two hydrogen atoms and so do the two molecules of water. Therefore, there are now four hydrogen atoms in both reactants and products.
    ::等式2显示氢的两个分子与一个氧分子发生反应,产生两个水分子。氢的两个分子各含有两个氢原子,水的两个分子也包含两个氢原子。因此,反应器和产品中现在都有四个氢原子。

    Q: Is equation 2 balanced?
    ::问题:等式2是否平衡?

    A: Count the oxygen atoms to find out. There are two oxygen atoms in the one molecule of oxygen in the reactants. There are also two oxygen atoms in the products, one in each of the two water molecules. Therefore, equation 2 is balanced.
    ::A: 计数氧原子。 反应器中氧的一个分子中有两个氧原子。 产品中还有两个氧原子, 两个水分子中各一个。 因此, 等式 2是平衡的 。

    Steps in Balancing a Chemical Equation
    ::平衡化学赤道的步骤

    Balancing a chemical equation involves a certain amount of trial and error. In general, however, you should follow these steps:
    ::平衡化学方程式涉及一定的尝试和错误。但一般来说,你应该遵循这些步骤:

    1. Count each type of atom in reactants and products. Does the same number of each atom appear on both sides of the arrow? If not, the equation is not balanced, and you need to go to step 2.
      ::在反应器和产品中计算每个原子类型。 箭头两侧的原子数量是否相同? 否则, 方程式是不平衡的, 您需要进入第2步 。
    2. Place coefficients, as needed, in front of the symbols or formulas to increase the number of atoms or molecules of the substances. Use the smallest coefficients possible. Warning! Never change the subscripts in chemical formulas. Changing subscripts changes the substances involved in the reaction. Change only the coefficients.
      ::需要时在符号或公式前面放置系数,以增加物质的原子或分子数量。 使用最小的系数 。 警告! 永远不要改变化学公式的下标。 修改下标会改变反应所涉的物质。 只修改系数 。
    3. Repeat steps 1 and 2 until the equation is balanced.
      ::重复步骤1和2,直到方程平衡。

    Q: Balance this chemical equation for the reaction in which nitrogen (N 2 ) and hydrogen (H 2 ) combine to form ammonia (NH 3 ):
    ::问题:在氮(N2)和氢(H2)结合形成氨(NH3)的反应中,平衡这一化学方程式:

    N 2 + H 2 → NH 3

    A: First count the nitrogen atoms on both sides of the arrow. There are two nitrogen atoms in the reactants so there must be two in the products as well. Place the coefficient 2 in front of NH 3 to balance nitrogen:
    ::A: 首先计算箭头两侧的氮原子。 反应器中有两个氮原子, 因此产品中也必须有两个。 将系数2放在 NH3 前面以平衡氮:

    N 2 + H 2 → 2 NH 3

    Now count the hydrogen atoms on both sides of the arrow. There are six hydrogen atoms in the products so there must also be six in the reactants. Place the coefficient 3 in front of H 2 to balance hydrogen:
    ::现在计数箭头两侧的氢原子。 产品中有6个氢原子, 所以反应器中也必须有6个。 将系数 3 放在 H2 前面以平衡氢 :

    N 2 + 3 H 2 → 2 NH 3

    Summary
    ::摘要

    • A chemical equation represents the changes that occur during a chemical reaction. It has the general form: Reactants → Products. All chemical equations must be balanced. This means that there must be the same number of each type of atom on both sides of the arrow.
      ::化学方程式代表化学反应期间发生的变化。 它具有一般形式 : 反应剂 + 产品 。 所有化学方程式都必须平衡。 这意味着箭头两侧的原子数量必须相同 。
    • Coefficients are used to balance chemical equations. A coefficient is a number placed in front of a chemical symbol or formula. It shows how many atoms or molecules of the substance are involved in the reaction.
      ::系数用于平衡化学方程式。系数是放在化学符号或公式前面的一个数字,它显示该物质有多少原子或分子参与反应。
    • To balance a chemical equation, place coefficients as needed in front of the symbols or formulas so the same number of each type of atom occurs in both reactants and products.
      ::为了平衡化学方程式,在符号或公式前按需要设定系数,以便在反应器和产品中出现每种原子数目相同的现象。

    Review
    ::回顾

    1. Which of the following chemical equations is balanced?
      1. Zn + HCl → ZnCl 2 + H 2
        ::Zn + HCl + ZnCl2 + H2
      2. 2 Zn + 2 HCl → ZnCl 2 + H 2
        ::2 Zn + 2 HCl + ZnCl2 + H2
      3. 2 Zn + HCl → ZnCl 2 + H 2
        ::2 Zn + HCl + ZnCl2 + H2
      4. Zn + 2 HCl → ZnCl 2 + H 2
        ::Zn + 2 HCl + ZnCl2 + H2

      ::下列哪些化学方程式是平衡的? Zn + HCl + ZnCl2 + H2 2 Zn + 2 HCl + ZnCl2 + H2 2 Zn + H2 + HCl + ZnCl2 + H2 ZnCl2+ H2 Zn + 2 HCl+ ZnCl2+ H2
    2. Balance this chemical equation: CH 4 + O 2 → CO 2 + H 2 O
      ::平衡这一化学方程式:CH4+O2+CO2+H2O
    3. Sam was given the following equation to balance: H 2 O → H 2 + O 2 . She balanced it as follows: 2 HO → H 2 + O 2 . What did she do wrong? What is the correct way to balance the equation?
      ::给萨姆平衡的方程式如下:H2O H2 + O2, 她平衡如下: 2 HO H2 + O2, 她做错了什么? 平衡方程式的正确方式是什么?

    Resources
    ::资源