Section outline

  • A historical laboratory scene with scientists discussing materials and conducting experiments.

    What might the scientists in this picture be discussing?
    ::照片中的科学家们会讨论什么?

    When the French scientist Antoine Lavoisier conducted his experiments, he did not know what the products of reactions were going to be.  He had to isolate the material (whether he was heating mercury or measuring from breathing) and then study its elemental composition before he could understand the processes that were occurring.
    ::当法国科学家安托万·拉沃伊瑟(Antoine Lavoisier)进行实验时,他不知道反应的产物会是什么。 他不得不分离物质(不管是加热汞还是从呼吸中测量汞),然后研究其元素构成,然后才能了解正在发生的过程。

    Discovering that a new exists is the start of a long project.  In order to make this new compound in the lab, we need to know a lot about its structure.  Often, the place to start is to determine the in the material.  Then we can find out the relative amounts of each element to continue our evaluation of this new material.
    ::发现新的存在是一个长期工程的开始。 为了在实验室中制造这个新的化合物, 我们需要了解它的结构。 通常, 起始点是确定材料中的内容。 然后我们可以找出每个元素的相对数量, 以继续我们对这一新材料的评估 。

    Empirical Formula
    ::经验公式

    An empirical formula is a formula that shows the elements in a compound in their lowest whole-number ratio. Glucose is an important simple sugar that cells use as their primary source of energy . Its is C 6 H 12 O 6 . Since each of the subscripts is divisible by 6, the empirical formula for glucose is CH 2 O. When chemists analyze an unknown compound, often the first step is to determine its empirical formula. There are a great many compounds whose molecular and empirical formulas are the same. If the molecular formula cannot be simplified into a smaller whole-number ratio, as in the case of H 2 O or P 2 O 5 , then the empirical formula is also the molecular formula.
    ::实证公式是一种公式,它以最低整数比率显示化合物中的元素。 葡萄糖是一个重要的简单糖, 细胞用它作为主要的能源来源。 它是C6H12O6。 由于每个下标可除以6, 葡萄糖的经验公式是CH2O。 当化学家分析未知化合物时, 第一步通常是确定它的经验公式。 许多化合物的分子和实证公式是相同的。 如果分子公式不能简化为较小的整数比率, 如H2O或P2O5, 那么实验公式也是分子公式。

    How would we determine an empirical formula for a compound? Let’s take a compound composed of carbon, hydrogen, and oxygen.  We can analyze the relative amounts of each element in the compound.  When we get a percent figure for each element, we now know how many grams of each are in 100 grams of the original material.  This allows us to determine the number of moles for each element.  The ratios can then be reduced to small whole numbers to give the empirical formula.  If we wanted a molecular formula, we would need to determine the molecular weight of the compound.
    ::我们如何为化合物确定一个实验公式? 让我们选择一个由碳、氢和氧组成的化合物。 我们可以分析化合物中每个元素的相对数量。 当我们获得每个元素的百分率时, 我们现在知道每个元素的克数以原始材料的100克为单位。 这使我们能够确定每个元素的摩尔数量。 然后, 比率可以降低为小数, 以给出实验公式。 如果我们想要一个分子公式, 我们需要确定化合物的分子重量 。

     

     

    Summary
    ::摘要

    • The empirical formula tells the lowest whole-number ratio of elements in a compound.
      ::实证公式显示化合物中元素的最小整数比率。
    • The empirical formula does not show the actual number of atoms.
      ::实证公式没有显示原子的实际数量。

    Review
    ::回顾

    1. Define “empirical formula.”
      ::“经验公式”的定义。
    2. Why is C 6 H 12 O 6 not considered to be an empirical formula for glucose?
      ::为什么C6H12O6不被视为葡萄糖的经验公式?
    3. Can the empirical formula for a compound be the same as the molecular formula?
      ::化合物的经验公式是否与分子公式相同?
    4. What do we need to know in order to determine a molecular formula from an empirical formula?
      ::为了从经验性公式中确定分子公式,我们需要知道什么?
    5. Give three examples of compounds whose empirical formulas are the same as their molecular formulas.
      ::举三个例子说明其实验公式与分子公式相同的化合物。