Acids, Bases, and Salts notes pdf 

• Introduction to Acids, Bases, and Salts
• Properties of Acids and Bases
• Chemical Reactions of Acids and Bases 
• pH Scale 
• Neutralization
• Salts 
• Preparation of Salts
• pH of Salts 
• Chemicals from Common Salt 
• pH Indicators
• Natural Indicators
• Importance of pH in Everyday Life

Acids, Bases, and Salts are three important types of chemical substances that we encounter in our daily lives. They have different properties and characteristics that make them unique.

 

Acids 

Acids are substances that have a sour taste and can dissolve metals, turn blue litmus paper red, and have a pH value less than 7. Examples of common acids include hydrochloric acid (HCl) found in our stomachs, sulfuric acid (H2SO4) used in car batteries, and acetic acid (CH3COOH) found in vinegar.

Base 

Bases are substances that have a bitter taste, feel slippery to the touch, and turn red litmus paper blue. They have a pH value greater than 7. Examples of common bases include sodium hydroxide (NaOH) found in drain cleaners, calcium hydroxide (Ca(OH)2) found in cement, and ammonia (NH3) found in cleaning products

Salts 

Salts are compounds formed when an acid reacts with a base. They are made up of positively charged ions (cations) and negatively charged ions (anions). Common examples of salts include sodium chloride (NaCl) found in table salt, calcium carbonate (CaCO3) found in chalk, and potassium nitrate (KNO3) found in fertilizers.

Properties of acids and bases 

Properties of acids:

Sour taste: Acids have a sour taste. For example, lemon juice, vinegar, and oranges are acidic in nature and have a sour taste.

Turn blue litmus paper red: Acids turn blue litmus paper to red. This is because they produce hydrogen ions (H+) when dissolved in water.

React with metals to release hydrogen gas: When acids react with metals like magnesium, zinc, and iron, they produce hydrogen gas.

Conduct electricity: Acids are good conductors of electricity when they are dissolved in water. This is because they produce ions when dissolved in water.

 Corrosive: Acids can corrode metals and other materials. For example, sulfuric acid is a highly corrosive acid and can burn through clothing and skin.

Properties of Bases: 

 Bitter taste: Bases have a bitter taste.For example, baking soda (sodium bicarbonate) has a bitter taste.

 Turn red litmus paper blue: Bases turn red litmus paper to blue. This is because they produce hydroxide ions (OH-) when dissolved in water.

 Slippery feel: Bases feel slippery or soapy to the touch.

Conduct electricity: Bases are good conductors of electricity when they are dissolved in water. This is because they produce ions when dissolved in water.

 Corrosive: Bases can also be corrosive. For example, sodium hydroxide is a highly corrosive base and can burn through clothing and skin. 

 

Chemical reactions of acids and base 

Reaction of acid with a base: When an acid reacts with a base, it results in the formation of salt and water. This type of reaction is called a neutralization reaction. The general equation for this reaction is:

 acid + base → salt + water 

 For example, when hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH), sodium chloride (NaCl) and water (H2O) are formed: 

 HCl + NaOH → NaCl + H2O

Reaction of acid with a metal: 

 When an acid reacts with a metal, it results in the formation of salt and hydrogen gas. The general equation for this reaction is:

 acid + metal → salt + hydrogen gas

  For example, when hydrochloric acid (HCl) reacts with zinc (Zn), zinc chloride (ZnCl2) and hydrogen gas (H2) are formed: 

 2HCl + Zn → ZnCl2 + H2

    Reaction of base with a non-metal oxide:

 When a base reacts with a non-metal oxide, it results in the formation of salt and water. The general equation for this reaction is:

 base + non-metal oxide → salt + water

  For example, when calcium hydroxide (Ca(OH)2) reacts with carbon dioxide (CO2), calcium carbonate (CaCO3) and water (H2O) are formed: 

 Ca(OH)2 + CO2 → CaCO3 + H2O

pH Scale 

The pH scale is a measure of the acidity or basicity of a solution. It ranges from 0 to 14, with 0 being the most acidic, 7 being neutral, and 14 being the most basic.

 For example, lemon juice has a pH of about 2.0, which means it is very acidic. On the other hand, baking soda has a pH of about 9.0, which means it is basic.

 Some other common examples of substances and their corresponding pH values are: 

•  Battery acid: pH 1.0 
•  Vinegar: pH 3.0 
•  Pure water: pH 7.0
•  Ammonia: pH 11.0
•  Bleach: pH 12.0

 It is important to note that the pH scale is logarithmic, which means that each whole number increase or decrease represents a tenfold increase or decrease in acidity or basicity. For example, a solution with a pH of 4.0 is ten times more acidic than a solution with a pH of 5.0.

Neutralization 

Neutralization is a chemical reaction between an acid and a base, resulting in the formation of salt and water. The reaction involves the transfer of H+ ions from the acid to the OH- ions from the base, forming water (H2O) and a salt. The salt formed depends on the specific acid and base used in the reaction. 

 The general equation for neutralization reaction is: 

 acid + base → salt + water

    For example, let's consider the neutralization reaction between hydrochloric acid (HCl) and sodium hydroxide (NaOH): 

 HCl + NaOH → NaCl + H2O 

 In this reaction, hydrochloric acid (HCl) is an acid and sodium hydroxide (NaOH) is a base. The reaction between them produces sodium chloride (NaCl), which is a salt, and water (H2O). Another example is the neutralization reaction between sulfuric acid (H2SO4) and calcium hydroxide (Ca(OH)2): 

 H2SO4 + Ca(OH)2 → CaSO4 + 2H2O

 In this reaction, sulfuric acid (H2SO4) is an acid and calcium hydroxide (Ca(OH)2) is a base. The reaction between them produces calcium sulfate (CaSO4), which is a salt, and water (H2O).  

Salts 

Salts are ionic compounds that are formed when an acid reacts with a base. Salts are composed of positively charged cations and negatively charged anions. 

 Types of Salts: There are three types of salts: acidic salts, basic salts, and neutral salts. 

 Acidic Salts: These are salts that are formed by the partial neutralization of an acid. They have a pH value less than 7.

 Basic Salts: These are salts that are formed by the partial neutralization of a base. They have a pH value greater than 7.

 Neutral Salts: These are salts that are formed by the complete neutralization of an acid and a base. They have a pH value of 7. 

 Examples of Salts: Some common examples of salts include sodium chloride (table salt), calcium carbonate (chalk), magnesium sulfate (Epsom salt), and potassium nitrate (saltpeter).

Properties of Salts 

Physical state: Most salts are crystalline solids at room temperature, although some are liquids or gases. The crystal structure of salts gives them a regular geometric shape with flat faces, sharp edges, and smooth surfaces. 

 Solubility: Salts are usually soluble in water, which means they can dissolve in water to form a solution. However, some salts are insoluble in water or only partially soluble. 

 Melting and boiling point: Salts have high melting and boiling points due to their strong ionic bonds. They require a lot of energy to break the electrostati c forces between the oppositely charged ions.

 Conductivity: Salts conduct electricity when dissolved in water or when in molten state because they dissociate into ions that can carry an electric current. However, they do not conduct electricity when in the solid state because the ions are not free to move. 

 Color: Salts can be colorless or have a characteristic color depending on the presence of impurities or the metal ions that make up the salt. 

 Reaction with acids and bases: Salts can react with acids and bases to produce different products. Neutralization reactions between an acid and a base produce salts and water. 

 Hygroscopicity: Some salts have the ability to absorb moisture from the air, which is called hygroscopicity. This property makes them useful as drying agents and preservatives.

pH of Salts 

The pH of salts depends on the nature of the cation and the anion in the salt.

 Neutral salts: Neutral salts do not have any acidic or basic properties and form neutral solutions. Examples of neutral salts are sodium chloride (NaCl), potassium nitrate (KNO3), and calcium chloride (CaCl2). The pH of a solution of a neutral salt is 7.

 Acidic salts: Acidic salts are formed when a weak acid reacts with a strong base. These salts contain a cation from the base and an anion from the acid. Examples of acidic salts are ammonium chloride (NH4Cl) and sodium dihydrogen phosphate (NaH2PO4). The pH of a solution of an acidic salt is less than 7. 

 Basic salts: Basic salts are formed when a weak base reacts with a strong acid. These salts contain a cation from the acid and an anion from the base. Examples of basic salts are sodium carbonate (Na2CO3) and calcium hydroxide (Ca(OH)2). The pH of a solution of a basic salt is greater than 7.

 It is important to note that the pH of a salt solution is not affected by the concentration of the salt in the solution. It only depends on the nature of the cation and the anion in the salt. 

 Uses of Salts 

Salts have a variety of uses, including in food preservation, fertilizers, water treatment, and as ingredients in many chemical processes.

Chemicals from common Salts

Common salts such as sodium chloride (NaCl), magnesium sulfate (MgSO4), and copper sulfate (CuSO4) can be used to prepare a variety of chemicals. Here are a few examples: 

 Hydrochloric acid (HCl): Sodium chloride (NaCl) can be reacted with sulfuric acid (H2SO4) to produce hydrochloric acid (HCl) and sodium sulfate (Na2SO4). 

NaCl + H2SO4 → Na2SO4 + 2HCl 

 Epsom salt (magnesium sulfate heptahydrate, MgSO4.7H2O): 

Magnesium sulfate can be obtained by reacting magnesium carbonate with sulfuric acid, or by adding magnesium oxide to dilute sulfuric acid. 

 MgCO3 + H2SO4 → MgSO4 + CO2 + H2O MgO + H2SO4 → MgSO4 + H2O

    Blue vitriol (copper sulfate pentahydrate, CuSO4.5H2O): 

Copper sulfate can be obtained by reacting copper oxide or copper carbonate with sulfuric acid. 

 CuO + H2SO4 → CuSO4 + H2O CuCO3 + H2SO4 → CuSO4 + CO2 + H2O

    Sodium hydroxide (NaOH): 

Sodium hydroxide can be obtained by the electrolysis of a solution of sodium chloride (brine) using a diaphragm cell.

 2NaCl + 2H2O → 2NaOH + H2 + Cl2

pH Indicator 

pH indicators are substances that change color in response to changes in the acidity or alkalinity (pH) of a solution. In Class 10, students typically learn about two common pH indicators: 

 Litmus: Litmus is a natural pH indicator that is derived from lichens. It is available as red and blue litmus paper. Red litmus paper turns blue in the presence of a basic (alkaline) solution, while blue litmus paper turns red in the presence of an acidic solution. 

 Methyl orange: Methyl orange is a synthetic pH indicator that is often used in laboratory experiments. It is red in acidic solutions (pH < 3.1) and yellow in neutral or slightly alkaline solutions (pH > 4.4). 

 Other pH indicators that are commonly used in laboratory experiments include phenolphthalein, bromothymol blue, and universal indicator. These indicators have a range of colors that correspond to different pH levels, and can be used to more precisely measure the pH of a solution.

Natural indicators for pH 

Natural indicators are substances that can be found in nature and can be used to determine the pH of a solution. They are different from synthetic indicators which are artificially made in a laboratory. Some common natural indicators are: 

 Litmus: Litmus is a water-soluble dye that is extracted from lichens. It is blue in alkaline solutions and red in acidic solutions. 

 Turmeric: Turmeric is a yellow spice that is commonly used in Indian cooking. It turns red in acidic solutions and yellow in alkaline solutions.

 Red Cabbage: Red cabbage contains a water-soluble pigment called anthocyanin. It turns red in acidic solutions, purple in neutral solutions, and green in alkaline solutions. 

 Beetroot: Beetroot is a vegetable that contains a water-soluble pigment called betalain. It turns red in acidic solutions and yellow in alkaline solutions. 

 Grape juice: Grape juice contains a pigment called anthocyanin. It turns red in acidic solutions and green in alkaline solutions.

 Blueberries: Blueberries contain a pigment called anthocyanin. It turns red in acidic solutions and green in alkaline solutions.

 These natural indicators can be used to test the pH of solutions in science experiments or in everyday life. However, their accuracy can be limited and may not be as precise as synthetic indicators.  

Importance of pH in everyday life

pH is an important concept in everyday life as it is a measure of the acidity or basicity of a solution. Here are some of the ways pH affects our daily lives: 

 In Agriculture: The pH of soil plays a crucial role in the growth of plants. Different plants require different levels of acidity or alkalinity in the soil to thrive. Farmers and gardeners often test the pH of the soil to determine what nutrients the soil needs and what crops will grow best.

 In Swimming Pools: pH levels are monitored and maintained in swimming pools to keep the water safe for swimmers. If the pH is too low, the water can be acidic and cause skin irritation and damage to the pool equipment. If the pH is too high, it can cause cloudiness and reduce the effectiveness of chlorine in killing bacteria.

 In Food and Beverages: pH levels are important in food and beverage production to ensure safety, flavor, and quality. For example, in the production of cheese and yogurt, pH is used to control the fermentation process. In the case of canned foods, a certain level of acidity is required to prevent bacterial growth and spoilage.

 In Human Body: pH is also important in the human body. The blood pH needs to be maintained within a narrow range of 7.35 to 7.45 for the body to function properly. Acidic blood can cause health problems like acidosis, and alkaline blood can cause alkalosis. 

 In Cleaning Products: pH plays a crucial role in determining the effectiveness of cleaning products.