Do you know what are the common methods of judging the positive and negative electrodes of primary batteries?

Everyone knows the battery, so do you know the primary battery? Can you judge the positive and negative electrodes of the primary battery? The primary battery reaction is an exothermic reaction, usually a redox reaction, but the difference from the general redox reaction is , the electron transfer is not completed by the effective collision between the oxidant and the reducing agent, but the reducing agent loses electrons on the negative electrode to undergo an oxidation reaction, the electrons are transported to the positive electrode through the external circuit, and the oxidant obtains electrons on the positive electrode to undergo a reduction reaction, thereby Complete the transfer of electrons between the reducing agent and the oxidizing agent.

Everyone knows the battery, so do you know the primary battery? Can you judge the positive and negative electrodes of the primary battery? The primary battery reaction is an exothermic reaction, usually a redox reaction, but the difference from the general redox reaction is , the electron transfer is not completed by the effective collision between the oxidant and the reducing agent, but the reducing agent loses electrons on the negative electrode to undergo an oxidation reaction, the electrons are transported to the positive electrode through the external circuit, and the oxidant obtains electrons on the positive electrode to undergo a reduction reaction, thereby Complete the transfer of electrons between the reducing agent and the oxidizing agent.

The directional movement of ions in the solution between the two poles and the directional movement of electrons in the external wire form a closed loop, which makes the two electrodes react continuously, and an orderly electron transfer process occurs, generating current and realizing the conversion of chemical energy to electrical energy.

However, it should be noted that non-redox reactions can also be designed as galvanic cells. From the perspective of energy conversion, the primary battery is a device that converts chemical energy into electrical energy; from the perspective of chemical reaction, the principle of the primary battery is that the electrons lost by the reducing agent in the redox reaction are transferred to the oxidant through an external wire, so that the redox reaction performed on the two electrodes, respectively.

Do you know what are the common methods of judging the positive and negative electrodes of primary batteries?

Condition of forming primary battery

(1) There are two metals with different activities (or one is a non-metal element or a metal oxide) as electrodes;

(2) The electrode materials are inserted into the electrolyte solution;

(3) The two poles are connected to form a closed circuit;

(4) Internal conditions: redox reaction can be carried out spontaneously.

As shown in the figure above, the composition of the primary battery:

(1) When the electrolyte solution is dilute H2SO4: the Zn electrode is the negative electrode, and its electrode reaction is Zn-2e- = Zn2+, which is an oxidation reaction; the Cu electrode is the positive electrode, and its electrode reaction is 2H+ +2e- =H2↑, This reaction is a reduction reaction.

(2) When the electrolyte solution is CuSO4 solution: the Zn electrode is the negative electrode, and its electrode reaction is Zn-2e- = Zn2+, which is an oxidation reaction; the Cu electrode is the positive electrode, and its electrode reaction is Cu2+ +2e- = Cu, the The reaction is a reduction reaction.

Judgment of positive and negative electrodes of primary batteries

1. According to the two electrode materials that make up the primary battery. Generally, the metal with strong activity is the negative electrode, and the metal with weak activity or non-metal that can conduct electricity is the positive electrode.

2. According to the current direction or the flow direction of electrons, the current flows from the positive electrode to the negative electrode; the electrons flow from the negative electrode to the positive electrode.

3. According to the direction of directional movement of ions in the electrolyte solution in the primary battery. In the electrolyte solution of the primary battery, the pole to which the cations move is the positive electrode, and the pole to which the anions move is the negative electrode.

4. Judging by the changes in the two poles of the primary battery. The negative electrode of the primary battery always loses electrons, and an oxidation reaction occurs, and the positive electrode always gains electrons, and a reduction reaction occurs.

5. According to the change of valence of substances in the overall battery reaction equation, the reaction with increasing valence is at the negative electrode, and the reaction with decreasing valence is at the positive electrode.

6. Judging according to whether the electrode material is dissolved or not. The negative electrode of the primary battery may be dissolved, but the positive electrode must not be dissolved; on the contrary, the one that increases in weight or releases air bubbles is the positive electrode.

7. Experimental method: Look at the direction of the deflection of the ammeter pointer. First use the known battery to verify the deflection direction of the ammeter pointer, and then determine the positive and negative electrodes of the primary battery according to the deflection direction of the ammeter pointer. The above is the method of judging the positive and negative poles of the primary battery, I hope it can help you in your study.

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