What are the reasons for the reaction of acid and salt to produce bubbles?

Answer 1

The reason for the bubbles formed by the reaction of acid and salt was mainly related to the principle of metathesis reaction.

First, from the nature of the reaction
1. Ion exchange and the properties of the products
- In the double decomposition reaction of acid and salt, it involved the exchange of ions. For example, the reaction between sulfuric acid and calcium dioxide (CaCO3 + 2HC1 = CaCl2 +CO2 ^+H2O). In the solution, sulfuric acid (HC1) dissociates into H and Cl. Although calcium dioxide (CaCO3) is difficult to dissolve, a small amount of it is dissolved in the solution and dissociates into Ca2 and CO2.
- When H and CO2 combine, they will form sulfuric acid (H ^CO). Because sulfuric acid is unstable, it is easy to decompose into carbon dioxide (CO2) and water (H ^O). The carbon dioxide escapes in the form of gas, creating bubbles.
2. The principle of strong acid making weak acid
- When a more acidic acid reacted with a salt corresponding to a weaker acid, if the conditions for a metathesis reaction were met, a reaction would occur and bubbles might be produced. For example, when sulfuric acid (a strong acid) reacted with sulfuric acid (CH COONa, which was a weak acid), the reaction equation was: HQ +CH COONa = CH COON +NaCl. This reaction did not produce bubbles. However, if it was the reaction of sulfuric acid and carbon dioxide (Na Chi CO), since carbon dioxide was a weaker acid than sulfuric acid, the reaction would produce carbon dioxide bubbles. The reaction equation was 2HQ +Na Chi CO = 2NaCl2 + H Chi O+ Na Chi CO.

Second, from the reaction conditions and equilibrium movement
1. The resulting gas leaves the system and causes the reaction to proceed in a positive direction
- In the reaction system, the generated gas (such as carbon dioxide) would escape from the solution. According to Le Chatelier's principle, this would cause the reaction equilibrium to continuously move in the direction of the generated gas, thus continuing to produce bubbles until the reaction was complete or one of the reagents was exhausted. For example, in the laboratory, carbon dioxide was produced from sulfuric acid and calcium carbonite. As the carbon dioxide continued to escape, the reaction would continue.
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