Topic 2 Neutralization reactions of acids and bases

Topic 2.

                             Neutralization of acids and bases

 1. neutralization reaction

 Acids have similar chemical properties, and bases have similar chemical properties. So, can acids and bases react?

 In the above experiment, the following reaction occurred to form sodium chloride and water:NaOH+HCl=NaCl+H2O

 In fact, other acids and bases can react similarly.

 It can be found that the sodium chloride, calcium chloride and sodium sulfate produced in the above reaction are all composed of metal ions and acid radical ions, and we call such compounds salts. Salt can dissociate metal ions and acid radical ions in aqueous solution. The reaction between acid and base to form salt and water is called neutralization reaction.

 2. Application of neutralization reaction in practice

 Neutralization reaction is widely used in daily life and industrial and agricultural productionIn agricultural production, the growth of crops has certain requirements for the acidity and alkalinity of the soil. According to the soil conditions, the neutralization reaction can be used to add acidic or alkaline substances to the soil to adjust the acidity and alkalinity of the soil to facilitate the growth of crops. For example, in recent years, acid rain has been formed due to air pollution, which has increased the acidity of the soil in some places, which is not conducive to the growth of crops, so people add an appropriate amount of slaked lime to the soil to neutralize the acidity.

 The sewage in the production process of the factory needs a series of treatment. For example, the sewage of a sulfuric acid plant contains sulfuric acid and other substances, which can be neutralized with slaked lime; the wastewater of a printing and dyeing plant is alkaline, and can be neutralized by adding sulfuric acid.

 Human gastric juice contains appropriate amount of hydrochloric acid, which can help digestion. However, if you eat too much, the stomach will secrete a large amount of gastric acid, which will cause stomach discomfort and indigestion. In this case, you can take certain medicines containing alkaline substances as directed by your doctor to neutralize the excess stomach acid.

 After a person is bitten by some mosquitoes, the mosquitoes secrete formic acid in the human skin, which makes the bite quickly swell into a big bag and itchy. If some solutions containing alkaline substances are applied, the pain and itching can be relieved.

 3. The expression of acidity and alkalinity of solution - pH

 We know that acids are acidic and bases are basic. In fact, there are many substances that are either acidic or alkaline. The acidity and alkalinity of a solution can be checked using an acid-base indicator. In life, production and scientific research, it is often necessary to accurately know the acidity and alkalinity of the solution, that is, the pH of the solution. So, how to measure and express the pH of the solution?

 The acidity and alkalinity of a solution is often expressed as pH , and the range of pH is usually 0 ~ 14 . The easiest way to measure pH is with pH paper.

 Understanding the acidity and alkalinity of solutions is of great significance to life, production and human life activities.

 In chemical production, many reactions must be carried out in a solution with a certain pH ; in agricultural production, crops are generally suitable for growing in soil with pH = 7 or close to 7 ; in acidic soil with pH < 4 or pH > 8 Alkaline soil is generally not suitable for planting . Adjusting soil pH is one of the ways to improve soil

 The acidic gas emitted by some factories is discharged into the air without treatment, which may lead to the increase of the acidity of the rainfall (pH of normal rainwater = 5.6), and we call the rainfall with pH < 5.6 acid rain. Acid rain is unfavorable to crops and some buildings. Monitoring the pH of rainwater at any time can help you understand air pollution and take necessary measures.

 The body fluids of healthy people must be maintained within a certain pH range, such as the pH of gastric juice at 0.9-1.5; if there is an abnormality, it may lead to disease. Measuring the pH of fluids in or out of the human body can help people understand the health of the body.

 After studying this topic, you should know

 1.Acids and bases can undergo neutralization reactions to form salt and water. Acid-base neutralization reaction is widely used in life and production.

 2.Salt is a compound that can dissociate metal ions and acid ions in aqueous solution.?

 3.The acidity and alkalinity of the solution can be expressed by pH , and the acidity and alkalinity of the solution can be measured with pH test paper. pH < 7, the solution is acidic;pH = 7, the solution is neutral;pH > 7, the solution is alkaline.

 4.Understanding the acidity and alkalinity of solutions is of great significance to life, production and human life activities.