Section outline

  • A mound of blue copper sulfate crystals on a surface.

    Why does the color change?
    ::为什么颜色变了?

    If you look at a typical bottle of copper sulfate, it will be a bluish-green.  If someone tells you that copper sulfate is white, you won’t believe them.  You are both right; it just depends on the copper sulfate.  Your blue-green copper sulfate has several water molecules attached to it while your friend’s copper sulfate is anhydrous (no water attached).  Why the difference? The water molecules interact with some of the d electrons in the copper and produce the color.  When the water is removed, the electron configuration changes and the color disappears.
    ::如果你看一下典型的铜硫酸盐瓶子, 它会是一个蓝绿色的。 如果有人告诉你铜硫酸盐是白色的, 你就不会相信它们。 您是对的; 它只是取决于铜硫酸盐。 您的蓝绿色铜硫酸盐在朋友的铜硫酸盐是无水的( 没有水附着的)时, 它有多种水分子附着在其中。 为什么区别? 水分子与铜中的一些d电子相互作用, 并产生颜色。 当水被去除时, 电子配置和颜色会发生变化 。

    Percent of Water in a Hydrate
    ::水中水分在水中的比例

    Many naturally contain water as part of the crystal lattice structure.  A hydrate is a that has one or more water molecules bound to each formula unit .  Ionic compounds that contain a transition metal are often highly colored.  Interestingly, it is common for the hydrated form of a compound to be of a different color than the anhydrous form, which has no water in its structure.  A hydrate can usually be converted to the anhydrous compound by heating.  For example, the anhydrous compound cobalt(II) chloride is blue, while the hydrate is a distinctive magenta color.
    ::水合物是一种与每个配方单元捆绑在一起的一个或多个水分子。含有过渡金属的离子化合物往往颜色高。有趣的是,一种化合物的水合物的颜色通常不同于其结构中没有水的无水体,水合物通常可以通过加热转换成无水化合物。例如,一种含水化合物的钴(II)氯化钴(II)是蓝色的,而水合物是一种独特的正红色。

    Anhydrous cobalt(II) chloride is blue; cobalt(II) chloride hexahydrate is magenta.

    On the left is anhydrous cobalt(II) chloride, CoCl 2 . On the right is the hydrated form of the compound called cobalt(II) chloride hexahydrate, CoCl 2 •6H 2 O.
    ::左侧是无水化钴(II)氯化物,CoCl2. 右侧是称为钴(II)氯化六氢酸盐的化合物的水化形式,CoCl2/6H2O。

    The hydrated form of cobalt(II) chloride contains six water molecules in each formula unit.  The name of the compound is cobalt(II) chloride hexahydrate and its formula is CoCl 2 •6H 2 O.  The formula for water is set apart at the end of the formula with a dot, followed by a coefficient that represents the number of water molecules per formula unit.
    ::氯化钴(II)的水化形式在每个公式单位中含有六个水分子,化合物的名称是氯化六氢酸钴(II),其公式是CoCl2/6H2O。水的公式在公式的末尾用点分隔,然后是代表每个公式单位水分子数量的系数。

    It is useful to know the percent of water contained within a hydrate.  The sample problem below demonstrates the procedure.
    ::了解水合物内含水量占水的百分比是有益的,下面的抽样问题说明了这一程序。

    Sample Problem One: Percent of Water in a Hydrate
    ::抽样问题一:水在水中的比例

    Find the percent water in cobalt(II) chloride hexahydrate, CoCl 2 •6H 2 O.
    ::查找氯化六氢酸钴(II)中的水量百分比,COCl2 6H2O。

    Step 1: List the known quantities and plan the problem.
    ::第1步:列出已知数量并规划问题。

    The mass of water in the hydrate is the coefficient (6) multiplied by the of H 2 O.  The molar mass of the hydrate is the molar mass of the CoCl 2 plus the mass of water.
    ::水合物中的水质量是系数(6)乘以H2O。水合物的摩尔质量是COCl2的摩尔质量加上水的质量。

    Known
    ::已知已知

    • mass of H 2 O in 1 mol hydrate = 108.12 g
      ::1毫摩尔水合物中的H2O重量=108.12克
    • molar mass of hydrate = 237.95 g/mol
      ::水合物摩尔质量=237.95克/摩尔

    Unknown
    ::未知

    • percent H 2 O = ? %
      ::H2O = = ?%

    Calculate the percent by mass of water by dividing the mass of H 2 O in 1 mole of the hydrate by the molar mass of the hydrate and multiplying by 100%.
    ::按水的质量计算百分比,将水合物的H2O质量除以1摩尔,将水合物的H2O质量除以水合物的摩尔质量,再乘以100%。

    Step 2: Calculate.
    ::第2步:计算。

    %   H 2 O = 108.12   g H 2 O 237.95   g × 100 % = 45.44 %   H 2 O

    ::H2O=108.12克 H2O237.95克克x10045.44% H2O

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

    Nearly half of the mass of the hydrate is composed of water molecules within the crystal.
    ::水合物质量的近一半是由水晶中的水分子构成的。

     

     

    Summary
    ::摘要

    • The process of calculating the percent water in a hydrate is described.
      ::描述了水合物中水分百分比的计算过程。

    Review
    ::回顾

    1. What is a hydrate?
      ::水合物是什么?
    2. How can you convert a hydrate to an anhydrous compound?
      ::你怎么能把水合物转换成无水化合物?
    3. What does hexahydrate mean?
      ::六氢酸盐是什么意思?