Question

Был он синий или красный, а в результате стал нейтральный. Вопрос: как называются такие реакции и к какому типу относятся?

Answer 1

Речь идёт про лакмус

Если среда кислая - лакмус красный

Если среда щелочная - лакмус синий

Если среда нейтральная - лакмус фиолетовый

Answer 2

Types of Reactions and their Classification

The reaction you are referring to, where a substance changes from one color to another and then becomes neutral, is known as a redox reaction. Redox is short for reduction-oxidation, which involves the transfer of electrons between chemical species.

In a redox reaction, one substance undergoes oxidation, which involves the loss of electrons, while another substance undergoes reduction, which involves the gain of electrons. The substance that is oxidized is called the reducing agent, while the substance that is reduced is called the oxidizing agent.

Redox reactions can be classified into different types based on the nature of the reactants and products involved. Some common types of redox reactions include:

1. Combination reactions: In these reactions, two or more substances combine to form a single product. For example, the reaction between iron and sulfur to form iron(II) sulfide:

   Fe(s) + S(s) → FeS(s)
   

2. Decomposition reactions: In these reactions, a single compound breaks down into two or more simpler substances. For example, the decomposition of hydrogen peroxide into water and oxygen gas:

   2 H2O2(aq) → 2 H2O(l) + O2(g)
   

3. Displacement reactions: In these reactions, an element displaces another element from a compound. For example, the reaction between zinc and hydrochloric acid to form zinc chloride and hydrogen gas:

   Zn(s) + 2 HCl(aq) → ZnCl2(aq) + H2(g)
   

4. Combustion reactions: In these reactions, a substance reacts with oxygen gas to produce carbon dioxide and water. For example, the combustion of methane:

   CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(g)
   

5. Neutralization reactions: In these reactions, an acid reacts with a base to form a salt and water. For example, the reaction between hydrochloric acid and sodium hydroxide to form sodium chloride and water:

   HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
   

It's important to note that the color change you mentioned may not always be a direct result of a redox reaction. Other factors, such as the presence of indicators or complex formation, can also cause color changes in chemical reactions.

Please let me know if there's anything else I can help you with!