The common forms of metal activity sequence table are as follows:
Potassium, calcium, sodium, magnesium, aluminum, zinc, iron, tin, lead (hydrogen), copper, mercury, silver and platinum
Potassium, calcium, sodium, magnesium, aluminum, zinc, iron, tin, lead (hydrogen), copper, mercury, silver, platinum and gold.
The metal activity decreases gradually from front to back.
The essence of metal activity sequence table arrangement is that the standard electrode potential is arranged from small to large and from negative to positive when the metal forms stable low-valent ions in aqueous solution. The so-called stable low-valent ions here refer to valence-changing metals. For example, iron is the standard electrode potential when ferrous ions are formed, and copper is the standard electrode potential when cuprous ions are formed, because cuprous ions are unstable in aqueous solution.
The measurement method of standard electrode potential is as follows: The primary battery consists of standard hydrogen electrode (E=0.000V) in standard state and electrodes of other metals, with the standard hydrogen electrode on the left and the metal on the right. The electromotive force of this battery is measured experimentally, and this electromotive force is the standard electrode potential (E) of the metal on this electrode.
The standard electrode potential values e of various metals measured by the above method are as follows:
EK+/K =-2.924v ECA 2+/Ca =-2.76v ENa+/Na =-2.7 109v
em G2+/Mg =-2.375v ea L3+/Al =- 1.706v ez N2+/Zn =-0.7628v
EFE 2+/Fe =-0.4402v es N2+/Sn =-0. 1346v EP B2+/Pb =-0. 1263v
EH+/H = 0.0000v ECU 2+/Cu = 0.3402v ehg 2+/Hg = 0.85 1V
EAg+/Ag = 0.7996v ept 2+/Pt = 1.2V EAu+/Au = 1.68v
Arranging the standard electrode potential of the metal protoacid from small to large is the metal activity sequence table.
With the metal activity sequence table, combined with the periodic law of elements, the activity of common metals is clear at a glance, which is very convenient to apply. The following problems can be well solved by using the metal active sequence table.
1, judging the activity of metal in aqueous solution.
This is the simplest and most intuitive application of metal activity sequence table. The higher the position of metal in the metal activity sequence table, the stronger the metal activity; The farther back the position, the weaker the metal activity. The more active the metal is, the easier it is to replace the hydrogen in the acid, and the more alkaline the corresponding oxide hydrate-hydroxide is.
2. Determine which metals can react with acids to produce hydrogen.
In the metal activity sequence table, the standard electrode potential of the metal before hydrogen is negative, so the reduced state (simple substance) can reduce hydrogen ions to generate hydrogen, while the metal after hydrogen cannot react with acid to generate hydrogen. Note that what is said here is that hydrogen cannot be produced, not that it does not react with acid.
3, judge the difficulty of metal and oxygen reaction and reaction products.
At room temperature, k ~ na can easily react with oxygen to generate oxides. If it is burned in oxygen or air, it will generate peroxides, even complex peroxides. Mg ~ Zn reacts very slowly with oxygen at room temperature, but can react violently at high temperature to form ordinary oxides. Fe ~ Ag usually does not react, but can only react in high temperature or pure oxygen, and the generated oxides are unstable and easy to decompose, such as mercury oxide decomposed at high temperature to obtain mercury and oxygen.
4. Judge the difficulty of the reaction between metal and water.
In the metal activity sequence table, K ~ Na reacts violently with cold water to generate alkali and hydrogen. Magnesium and hot water produce alkali and hydrogen at a low rate; Al ~ Pb reacts with high temperature steam to generate metal oxides and hydrogen, such as iron reacts with high temperature steam to generate ferroferric oxide and hydrogen.
5, the judgment of nitrate decomposition products
In the metal activity sequence table, the nitrate of k ~ na is decomposed by heating to produce nitrite and oxygen; Nitrate of mg ~ Cu is decomposed by heating to produce metal oxide, nitrogen dioxide and oxygen; Nitrates of silver and mercury are decomposed by heating to produce metal elements, nitrogen dioxide and oxygen. Nitrate is a strong oxidant when heated, because it decomposes to produce oxygen when heated.
6. Judge the positive and negative poles of the primary battery.
In a galvanic cell, metals or metals with different activities and other materials are the two electrodes of the galvanic cell. The more active metal loses electrons to form ions into the solution, and the electrons move directionally from the low potential electrode to the high potential electrode through the external circuit to generate current. The electrode where electrons flow out is the negative electrode of power supply, and the electrode where electrons flow in is the positive electrode of power supply. Therefore, the two kinds of metal electrodes have different activities, and the metal with higher activity is the negative electrode. It is worth noting that the activity of metal is also related to the electrolyte properties of chemical power supply, such as copper-aluminum primary battery, with sodium hydroxide as electrolyte and al as negative electrode; Concentrated nitric acid is used as electrolyte and copper is used as negative electrode.
In addition to the above list, the metal activity sequence table can also be used to judge the occurrence of chemical reactions, help us understand and master the discharge order of cations in the electrolysis process, and judge the electrolytic products.
Although the metal activity sequence table has the above-mentioned extensive uses, it still has certain limitations, and the following aspects should be paid attention to when applying it:
1. The metal activity sequence is arranged according to the standard electrode potential, and only the possibility of redox reaction is pointed out from the thermodynamic point of view, which only refers to the size of the reaction trend and cannot explain the reaction rate.
Secondly, the order of metal activity is from easy to difficult according to the trend of forming stable low-valent ions in aqueous solution, which is not suitable for non-aqueous solution and high-temperature solid-state reaction.
Thirdly, the products of the reaction between metal and acid are related to the oxidation degree, concentration and temperature of acid, which should be treated differently and cannot be generalized.
In short, the activity sequence table has a complete and systematic scientific theoretical basis and a wide range of applications. We should apply what we have learned and give full play to the guiding role of this scientific theory in practice.