- A. sour
- B. sweet
- C. bitter
- D. salty
(a) sour
- A. acid
- B. base
- C. salt
- D. salt and base
(d) salt and base
- A. blue
- B. green
- C. red
- D. white
(c) red
- A. OH –
- B. H +
- C. OH
- D. H
(a) OH
- A. acid
- B. base
- C. oxide
- D. alkali
(d) alkali
- A. acetic acid
- C. oxalic acid
- D. formic acid
(d) formic acid
- A. acidity
- B. head pain
- C. teeth decay
- D. None of these
(a) acidity
- A. salt and water
- B. salt
- C. water
- D. no reaction
(a) salt and water
- A. basic
- B. acidic
- C. both a and b
- D. none of these
(a) basic
- A. blue
- B. green
- C. yellow
- D. red
(d) red
Acidus.
CaO.
Deep pink or deep red.
This statement is false. Most of the acids are soluble in water. Acids such as hydrochloric acid, sulphuric acid, nitric acid, and acetic acid are highly soluble in water. When acids dissolve in water, they ionize and release hydrogen ions, which give acids their characteristic sour taste and corrosive properties. However, some acids like silicic acid have limited solubility in water. The solubility of acids in water is an important property that allows them to be used in various chemical reactions and applications.
This statement is false. The correct statement is that acids are sour in taste, not bitter. Sourness is the characteristic taste property of acids due to the presence of hydrogen ions. Common examples include vinegar, lemon juice, and citric acid, which all taste sour. Bases, on the other hand, are bitter in taste. Bases such as sodium hydroxide and ammonia solution have a bitter taste. It is important to distinguish between the taste properties of acids and bases, as this is one of the key ways to identify them in laboratory settings.
This statement is false. The correct statement is that bases are soapy to touch only when they are in aqueous solution or wet form, not when they are dry. When bases are dissolved in water or present in aqueous media, they feel slippery and soapy to the touch due to their ability to saponify oils and fats on the skin. However, when bases are in their dry or solid state, they do not exhibit this soapy feeling. For example, solid sodium hydroxide does not feel soapy until it comes into contact with moisture or water. This soapy feeling is a characteristic property of bases in aqueous solution and is useful for identifying bases in laboratory work.
This statement is true. Acids are corrosive in nature, meaning they can damage or destroy materials they come into contact with. Strong acids such as sulphuric acid and hydrochloric acid are highly corrosive and can burn skin, corrode metals, and damage organic materials. Even dilute acids can be corrosive to certain substances. This corrosive property of acids is due to the presence of hydrogen ions that react with various materials. The corrosive nature of acids makes them dangerous to handle and requires proper safety precautions such as wearing protective equipment and using appropriate containers for storage and transport.
This statement is false. The correct statement is that all alkalis are bases, but all bases are not alkalis. A base is a substance that can neutralize an acid and produce salt and water. Bases include metal oxides, metal hydroxides, and ammonia. An alkali is a specific type of base that is soluble in water and produces hydroxide ions. Common alkalis include sodium hydroxide, potassium hydroxide, and ammonia solution. Since all alkalis are soluble bases that produce hydroxide ions in water, they are all bases. However, not all bases are alkalis because some bases like metal oxides are insoluble in water and do not produce hydroxide ions directly. Therefore, the relationship between bases and alkalis is that alkalis form a subset of bases, not the other way around.
True. Hibiscus flower is indeed a natural indicator because it contains pigments that change color in the presence of acids and bases. The petals of hibiscus flowers contain anthocyanins, which are natural pH-sensitive compounds. When exposed to acidic solutions, hibiscus petals turn pink or red, while in basic solutions they turn blue or greenish. This color-changing property makes hibiscus flowers useful for identifying whether a substance is acidic or basic, making it a reliable natural indicator for laboratory and educational purposes.
An acid is a substance which contains one or more replaceable hydrogen atoms that can be released when the acid reacts with a base or other substances. When dissolved in water, acids ionize to produce hydrogen ions (H⁺), which are responsible for their characteristic sour taste and acidic properties. Common examples of acids include hydrochloric acid, sulfuric acid, acetic acid, and citric acid. Acids are classified as strong or weak depending on the degree to which they ionize in aqueous solution.
Acids are sour in taste, which is one of their most recognizable properties. They are corrosive in nature, meaning strong acids can spoil and damage substances like human skin, clothes, and paper. Generally acids exist in liquid state, but a few acids exist in solid state too, such as benzoic acid and oxalic acid. Acids are typically colorless in their pure form. Acids change the color of indicators, which is a key property used to identify them. Blue litmus paper turns red when treated with acids, and methyl orange turns pink or red in acidic solutions. These color changes occur because acids contain hydrogen ions that react with the dye molecules in the indicators, altering their chemical structure and thus their color.
Acids and bases share several important similarities. Both are corrosive in nature and can damage living tissues and materials. They both undergo ionization in aqueous solution, meaning they break apart into ions when dissolved in water. Both acids and bases conduct electricity in aqueous solution because of the presence of ions. Additionally, both acids and bases undergo neutralization reaction with each other, in which they react to form water and salt, effectively canceling out each other's properties.
Difference between acids and bases:
Acids:
They produce H + ions in water.
They are sour in taste.
Few acids are in solid state.
Acids turn blue litmus paper red.
Bases:
They produce OH – ions in water.
They are bitter in taste.
Most of the bases are in solid state.
Bases turn red litmus paper blue.
A neutralization reaction is a chemical reaction in which an acid and a base react with each other to form water and salt as products. In this reaction, the hydrogen ions from the acid combine with the hydroxide ions from the base to produce water molecules. The remaining ions combine to form a salt. For example, when hydrochloric acid reacts with sodium hydroxide, it produces sodium chloride (salt) and water. Neutralization reactions are important in many practical applications, such as treating acid indigestion with antacids and neutralizing industrial waste.
Bases generally exist in solid state, but some bases exist in liquid state also, such as ammonium hydroxide and calcium hydroxide. Bases give a soapy or slippery touch only in aqueous media and not in their dry state. Bases are bitter in taste, which distinguishes them from acids that are sour. Bases are corrosive in nature, and when they come in contact with the skin frequently, they can form painful blisters and cause chemical burns. Bases also change the color of indicators, which is an important property for identifying them. Red litmus paper turns blue when treated with bases. Similarly, bases turn methyl orange from red to yellow and phenolphthalein from colorless to pink. These color changes occur because bases contain hydroxide ions that react with the dye molecules in the indicators.
Hydrochloric acid present in our stomach helps in the digestion of foodstuff.
Vinegar (acetic acid) is used to preserve food materials.
Benzoic acid is also used to preserve food materials like pickles.
Sodium or potassium salts of higher fatty acids are used to make washing and bathing soaps.
Sulphuric acid is called the king of chemicals. It is an effective dehydrating agent. It is used in various industries to make detergents, paints, fertilizers and many more chemicals.
Hydrochloric acid, Nitric acid and Sulphuric acid are important laboratory reagents.
Cells of all living organisms contain the fundamental nuclear material called nucleic acids. Animals have deoxyribo nucleic acid (DNA) whereas plants contain ribo nucleic acid (RNA).
Bases have numerous important uses in everyday life and industry. Potassium hydroxide is used to make bathing soaps, which are essential personal care products. Sodium hydroxide is used to make washing soaps and detergents for cleaning purposes. Sodium hydroxide is also widely used in paper industries for pulping wood, in textile industries for processing fabrics, and in the preparation of various medicines and pharmaceuticals. Calcium hydroxide is used for white washing walls and buildings, and it also serves as a component in cement and mortar. Aluminum hydroxide and magnesium hydroxides are used in antacids to cure acidity problems and provide relief from indigestion. Ammonium hydroxide is used to manufacture fertilizers for agriculture, and in the production of nylon, plastics, and rubber materials. These diverse applications demonstrate the importance of bases in modern industry and daily life.
1. Ant bite:
Whenever bees or red ants bite they inject an acid called formic acid.
These acids cause burning sensation and pain.
To suppress the pain, a suitable base in the form of calcium hydroxide (readily available at home) is applied to neutralise the formic acid.
2. Wasp bite:
When we are bitten by wasp, we feel the burning sensation and pain. It is due to an alkaline substance injected by the insect.
To neutralise the alkalinity, we use vinegar which is an acid.
3. Tooth decay:
The bacteria present in our mouth decompose the food particles stuck in the gaps between our teeth thereby causing acid formation which leads to tooth decay.
When we brush with tooth powder or tooth paste containing weak bases, the acid gets neutralized.
4. Acidity:
Excessive production of hydrochloric acid in our stomach causes ulcer in stomach and food pipe.
In order to neutralize, antacids which are nothing but weak bases like aluminum and magnesium hydroxides are used.
5. Agriculture:
Farmers add lime fertilisers such as powdered lime (CaO), limestone (CaCO 3 ) or ashes of
burnt wood to the soil to neutralise the acidity.
6. Industries:
Effluents from the industries contain acids such as sulphuric acid. It is treated by adding lime to neutralise it before it is discharged into rivers and streams.
Turmeric indicator is one of the most commonly used natural indicators. To prepare it, a small amount of water is added to turmeric powder to form a paste. This paste is then applied on a blotting paper or filter paper and dried completely to create indicator strips. These strips are used to find the nature of solutions by observing color changes. In acidic solutions, the turmeric indicator paper shows no change in color and remains yellow because turmeric does not react with acids. In basic or alkaline solutions, the color changes dramatically from yellow to red or reddish-brown. This color change occurs because the curcumin compound present in turmeric reacts with bases, altering its molecular structure and producing a different color. This simple and safe method makes turmeric an excellent natural indicator for educational purposes and for testing the pH of various solutions.
Both lemon rice and curd rice taste sour because they contain acids. Curd contains lactic acid, which is produced by the fermentation of milk by lactic acid bacteria. The lactic acid makes curd rice sour in taste. Lemon juice contains citric acid, which is a naturally occurring organic acid found in citrus fruits. The citric acid makes lemon rice sour in taste. Generally, acids are sour in taste, which is one of their characteristic properties. The sourness we perceive is due to the presence of hydrogen ions released by these acids when they come into contact with taste receptors on our tongue. Different acids produce different levels of sourness depending on their strength and concentration. This is why lemon juice tastes more intensely sour than curd, as citric acid is a stronger acid than lactic acid.
Dental caries, commonly known as tooth decay or cavities, is caused by the action of acids on the enamel surface of teeth. The acid is produced when sugar in foods or drinks reacts with bacteria present on the tooth surface. Bacteria in the mouth metabolize sugars and produce acids as a byproduct, which gradually dissolve the tooth enamel. Heshna has developed caries because she has not cleaned her teeth well after consuming sugary drinks and snacking. When sugar remains on the teeth, bacteria continue to produce acids that attack the enamel. In contrast, Keerthi's teeth are white and free from caries because she maintains good oral hygiene. To prevent tooth decay, it is essential to brush teeth after meals and before bed to remove food particles and bacteria. Regular brushing helps remove the plaque that harbors bacteria and prevents acid formation. Additionally, limiting sugary foods and drinks, and using fluoride toothpaste can help strengthen tooth enamel and prevent caries.