铬酸盐配方——结构、性质、用途、示例问题

铬酸盐化合物由铬和氧元素组成。铬是一种钢灰色、坚硬、易碎且有光泽的过渡金属。它的原子序数是24，用符号Cr表示。它主要用于合金中以增加强度和耐腐蚀性。氧气是一种高反应性的非金属和氧化剂，可与许多元素/化合物形成氧化物。它的原子序数为 8，用符号 O 表示。氧是元素周期表中硫属元素族的成员。

铬酸盐配方

铬酸盐是含有铬酸根阴离子的铬酸盐。它是铬的氧代阴离子和通过从铬酸中去除两个质子而产生的二价无机阴离子。其化学式为CrO ₄ ^2- 。它是用于产生不溶性盐的众多多原子离子之一。一些铬酸盐是钠盐和钾盐。铬酸盐是一种强氧化剂，通常呈深黄色。

铬酸盐的结构

铬酸盐的物理性质

Appearance	Yellow powder
Odor	Odorless
Molecular Weight	115.9921 g/mol
Solubility	Insoluble in water
Valency	2

铬酸盐的化学性质

• 铬酸根离子在酸溶液中起强氧化剂的作用。在碱性溶液中铬酸根离子与水结合形成氢氧化铬(III)。

CrO₄^2- + 4H₂O + 3e^– ⇢ Cr(OH)₃ + 5OH^–

• 作为钾盐的铬酸盐与硝酸钡反应生成铬酸钡和硝酸钾，反之亦然。

K₂CrO₄ + Ba(NO₃)₂ ⇠⇢ BaCrO₄ + 2KNO₃

• 铬酸盐与过氧化氢反应生成一种化合物，其中一个或多个氧原子被过氧化物取代。

铬酸盐的应用

1. 由于铬酸钠和钾盐具有高度腐蚀性，因此可用于搪瓷、涂饰皮革和金属防锈。
2. 铬酸钾晶体用作油墨和染料中的颜料。如果食用它是有毒的/有毒的。
3. 铬酸盐用于镀铬以消除腐蚀。
4. 铬酸铅用于制造不安全的工业蜡笔。

示例问题

问题1：我们如何区分化合物铬酸盐和重铬酸盐？

回答：

The compounds can be distinguished by their appearance. Chromate appears in bright yellow and where as Dichromate appears in orange color.

问题2：铬酸盐是酸还是碱？

回答：

Chromate is a base because chromate ion is predominant species in alkaline solution. Where as Dichromate is acidic because it was the predominant species in acidic solution.

问题3：为什么铬酸钾呈黄色？

回答：

Initially Potassium Chromate is orange in color but it turns out into yellow when sodium hydroxide is introduced. It replaces the hydrogen ions from the solution.

问题4：铬酸钾在哪里使用？

回答：

Potassium Chromate is used as pigment in making paints, inks. It is also used as fungicide in chemical processing. It is carcinogenic and an oxidizing agent.

问题 5：铬和铬酸盐有区别吗？

回答：

Yes. They both are different. Chromium is an item that is applied as an electroplated finish. At the other hand Chromate characterize the process resistant to corrosion which is known as conversion finish.

问题6：铬酸盐的矿物质是什么？

回答：

Minerals containing chromium element are not common very few are present. The most common one is crocoite. It occurs as magnificent long red crystals. It’s chemical formula is PbCrO₄. Rarely potassium chromate minerals are founded in Atacama desert. Finally the only known dichromate mineral is Lopezite.

问题7：计算CrO ₄ ^-2的分子量？

回答：

Molecular weight of Chromium (Cr) = 51.9961

Molecular weight of Oxygen (O) = 15.999

There are 1 Chromium 4 Oxygen atoms in Chromate compound

Total molecular weight = 51.9961 + (4 × 15.999)

= 51.9961 + 63.996

= 115.9921

Molecular weight of CrO₄^-2 is 115.9921 g/mol