DAV Class 7 Science Chapter 4 Acids, Bases and Salts Question Answer Notes
DAV Class 7 Science Chapter 4 Acids, Bases and Salts Question Answer Notes Solution by Expert Science Teacher. DAV Class 7 Science 4th Chapter Acids, Bases and Salts for Students of DAV Schools.
Lesson No 4
Acids, Bases and Salts
A.) Fill in the blanks.
Answer: (1) organic acids (2) bitter, soapy (3) red (4) salt, water (5) nitrate (6) acetic acid, sodium hydroxide
B.) Match the following.
1. Lemon juice | (a) Oxalic acid |
2. Tamarind | (b) Lactic acid |
3. Vinegar | (c) Citric acid |
4. Red ants | (d) Acetic acid |
5. Sour milk | (e) Tartaric acid |
6. Guava | (f) Formic acid |
Answer:
C.) Tick the correct option.
Answer:
1.) bitter taste and a soapy feel
2.) litmus
3.) citric acid
4.) nitric acid
5.) salts
6.) turmeric
7.) sour and bitter
D.) Answer the following questions in brief.
1.) What are mineral acids?
One kind of acid that comes from inorganic substances is called a mineral acid. Examples include phosphoric, sulfuric, nitric, and hydrochloric acids. Numerous industrial, commercial, and laboratory uses are possible for these acids.
2.) Give two examples each of mineral acids and organic acids.
Answer: Mineral Acids: 1. Hydrochloric acid 2. Sulfuric acid Organic Acids: 1. Acetic acid 2. Formic acid
3.) Name any two substances that can be used as indicators.
Answer: Litmus paper and turmeric.
4.) Write the meaning of the term ‘neutralisation reaction.
A chemical reaction known as a neutralisation reaction occurs when an acid and a base combine to produce salt and water. The hydrogen ion from the acid is swapped out for the hydroxide ion from the base in this reaction between an acid and a base. A salt and water are produced as a result of this reaction.
5.) Give any two properties of salts.
Answer: 1.) Salts are mostly soluble in water.
2.) Salts might be rystalline solids under general conditions.
6.) Classify the following salts as neutral, acidic or basic. Also, write their names.
(a) Na3PO4
(b) K2CO3
(c) NH4NO3
Answer:
(a) Sodium Phosphate; neutral salts.
(b) Potassium carbonate; basic salts.
(c) Ammonium nitrate; acidic salts.
E.) Answer the following questions.
1.) All alkalies are bases but all bases are not alkalies. Justify this statement.
Answer: Alkalis are bases that are soluble in water. But however all bases do not dissolve with water hence are insoluble.However , all alkalis have the basic property of a base and can neutralise an acidic solution.
2.) Suggest an activity that can help one to decide whether a given solution is acidic or basic in nature.
Answer: Litmus paper test and give us an idea whether a solution is acidic or basic in nature. when the litmus paper is dipped in the solution if it turns pink in colour then the solution is acidic in nature. if it turns blue in color this means that the solution is basic in nature
3.) Write chemical equations for the following reactions:
Answer:
(a) Ca(OH)2 + 2HNO3 → Ca(NO3)2 + 2H2O
(b) 2CH3COOH + Ca(OH)2 → Ca(CH3COO)2 + 2H2O
(c) HCl + NaOH → NaCl + H2O
(d) 2NH4OH + H2SO4 → (NH4)2SO4+ 2H2O
4.) State the difference between neutral, acidic and basic salts. Give one example of each.
Answer:
- Neutral salts are formed by the reaction of strong acid with a strong base
- basic salts are formed by the reaction of weak acid and strong
- basic salts are formed by the reaction of weak acid and strong base acidic soils are formed by the reaction of strong acid and a weak base
5.) Describe an activity to show that solutions of salts, in water, can conduct electricity.
Answer: A simple experiment can be conducted for which one will need a beaker, water, some table salt or sodium chloride. We shall also require a light bulb and battery . We need to half fill the beaker with the water containing dissolved sodium chloride. We will have to attach graphite rods that will be used as cathodes to the battery terminals and connect it with the bulb. After this it is required to submerge the rods within the solution. As we conduct the experiment we will soon observe that the bulb starts glowing thereby indicating that electricity has been passing as it has been conducted by the solution.
More Extra Questions for Preparation
Q.1) Fill in the blanks.
1.) Sulphuric acid is known as king of chemicals.
2.) Bases which are soluble in water are called alkalis.
3.) A chemical reaction between acid and base is called neutralization reaction.
4.) Litmus can be used as an indicator in the form of a solution.
Q.2) Match the following.
1. China rose | a) Neutral salt |
2. Sodium hydroxide | b) Sour in taste |
3. Acid | c) Base |
4. Sodium acetate | d) Indicator |
5. Sodium chloride | e) CH3COONa |
Answer= 1 – d, 2 – c,3 – b, 4 – e, 5 – a.
Q.3) Define the following.
1.) Organic acids.
Answer=Acids which are naturally occurring and are found in plants and animals, are called organic acids.
2.) An indicator.
Answer=An indicator is a substance which shows different in colours in an acidic and a basic medium.
Q.4) True or false with reason for false answer.
1.) Red ants contain formic acid.
Answer= True.
2.) Bases are insoluble in water.
Answer=False.
Reason: Bases are soluble in water.
3.) Turmeric acts as an indicator.
Answer= True.
4.) Litmus is purple in color.
Answer= True
5.) Sour milk contains acetic acid.
Answer= False
Reason: Sour milk contains lactic acid.
Q.5) Answer the following.
1.) Write the properties of salts.
Answer=1. Salts are formed through reactions between acids and bases.
2.) Most of the salts are readily soluble in water.
3.) Salts do not conduct electricity in their solid state. However, molten salts and solution of salts in water conduct electricity.
2) How salts are classified? Explain.
Answer= Salts are classified as neutral, acidic and basic.
1.) Neutral salts:- Salts formed by the reaction of a strong acid with a strong base are neutral salts.
Examples of neutral salts are Sodium chloride.
2.) Acidic salts:- Salts formed by the reaction of a strong acid and a weak base are acidic salts.
Examples of acidic salts are Aluminum chloride.
3.) Basic salts:- Salts formed by the reaction of a weak acid and a strong base are basic salts.
Examples of basic salts are Sodium acetate.
3.) Role of hydrochloric acid.
Answer=
1.) Hydrochloric acid present in small quantities in our stomach.
2.) It helps in digestion of food.
3.) However, when an excess of this acid gets secreted in the stomach, it causes nausea and pain in stomach.
4.) Antacids are used to cure the problem.
5.) Antacids contain mild base which neutralizes the excess acid present in the stomach.
Q.6) Complete the following.
1.) Salts of carbonic acids are named as
Answer= Carbonates.
2.) Mg (OH) 2 + 2HNO3
Answer= Mg (NO3)2 + 2H2O
3.) Strong base
Answer= Potassium hydroxide.
4.) Vinegar contains
Answer= Acetic acid.
5.) Mineral acid
Answer=Hydrochloric acid (HCL)
6.) Acids having low concentration are called
Answer=Dilute acids.
Q.7) What are indicators? Give examples of indicators.
Answer= 1.) An indicator is a substance which shows different colours in an acidic and basic medium.
2.) The colour of the indicator can thus help in identifying acids and bases.
3.) An indicator used very often is litmus.
4.) Litmus can be used as an indicator in form of solution.
Examples of indicator are Turmeric, juice of China rose.