Question

write any 10 own questions and answers from lesson acids bases and salts class 7​

Answer 1

Answer:

1. State differences between acids and bases.

Solution:

Acids Bases

Acids are sour in taste Bases are bitter in taste

Acids turn blue litmus paper into red color The base does not change the colour of blue litmus paper

Acids does not change the colour of the red litmus Bases turn red litmus paper to blue color

Acids do not change the colour of turmeric Bases turn turmeric to red

2. Ammonia is found in many household products, such as window cleaners. It turns red litmus blue. What is its nature?

Solution:

The answer is basic in nature

3. Name the source from which litmus solution is obtained. What is the use of this solution?

Solution:

Litmus solution is extracted from lichens. Litmus solution is used as an indicator to find acidic and basic nature of a solution.

4. Is the distilled water acidic/basic/neutral? How would you verify it?

Solution:

Distilled water is neutral in nature, and this can be tested by using red and blue litmus paper. In either of the cases, colour remains unchanged.

5. Describe the process of neutralisation with the help of an example.

Solution:

Neutralisation is a reaction between an acid and a base. Here both acids and bases get neutralised. For example, when sodium hydroxide (NaOH) is added to hydrochloric acid (HCl), sodium chloride (NaCl) and water (H2O) are obtained.

NaOH + HCl → NaCl + H2O + Heat

6. Mark ‘T’ if the statement is true and ‘F’ if it is false:

(i) Nitric acid turn red litmus blue. (T/F)

(ii) Sodium hydroxide turns blue litmus red. (T/F)

(iii) Sodium hydroxide and hydrochloric acid neutralise each other and form salt and water. (T/F)

(iv) Indicator is a substance which shows different colours in acidic and basic solutions. (T/F)

(v) Tooth decay is caused by the presence of a base. (T/F)

Solution:

i) False

ii) False

iii) True

iv) True

v) False

7. Dorji has a few bottles of soft drink in his restaurant. But, unfortunately, these are not labelled. He has to serve the drinks on the demand of customers. One customer wants acidic drink, another wants basic and third one wants neutral drink. How will Dorji decide which drink is to be served to whom?

Solution:

Dorji can taste a few drops out of soft drinks bottles, acidic solution is sour in taste, basic solution is bitter in taste, and the neutral solution has no taste. Along with tasting, Dorji can use litmus paper to test the nature of soft drink. He should use blue litmus paper to test the acidic solution. Dorji has to put a drop of solution on blue litmus. If it turns red then the solution will be acidic in nature.

Similarly, he can use red litmus paper to test the basic solution. He has to put a drop of solution on red litmus. If it turns blue then the solution will be basic in nature.

8. Explain why:

(a) An antacid tablet is taken when you suffer from acidity

(b) Calamine solution is applied on the skin when an ant bites.

(c) Factory waste is neutralised before disposing it into the water bodies.

Solution:

The antacid tablet contains base like milk of magnesia which neutralises the acid produced in the stomach. Hence, it is used while suffering from acidity.

When ant bites, it injects formic acid inside the skin. Calamine consists of Zinc carbonate which is basic in nature. Hence calamine neutralises the effect of formic acid to bring relief for the affected person.

Factory wastes are acidic in nature which may cause harm to the aquatic life. Hence, they are neutralised by using a base before disposing it into the water bodies.

9. Three liquids are given to you. One is hydrochloric acid, another is sodium hydroxide and third is a sugar solution. How will you identify them? You have only turmeric indicator.

Solution:

The following steps are taken to test the given liquids:

Put a drop of provided liquid on the turmeric indicator. The solution that changes the colour of the indicator to red, is sodium hydroxide, which is basic in nature.

Now, to make two mixtures, add a drop of sodium hydroxide on the other two liquids individually.

The drop of each combination added to the turmeric indicator one after another.

The mixture that changes the indicator to red colour includes a neutral solution of sugar.

While the mixture contains hydrochloric acid that has been neutralized by the addition of sodium hydroxide, which does not show any colour change in the indicator.

10. Blue litmus paper is dipped in a solution. It remains blue. What is the nature of the solution? Explain.

Solution:

Above solution may be neutral or basic in nature as both of them will not change the colour of the blue litmus paper.

Answer 2

Acids, Bases, and Salts is a chapter that deals with the physical, chemical, and reactive properties of chemicals/substances.

• Some of the questions that can be asked in this chapter are:

1. Define acids with an example.
2. Define base with an example.
3. How are salts formed?.
4. Illustrate what kind of reaction: 2NaOH + Zn → Na₂ZnO₂ + H₂
5. Give a few examples of acids and bases that are found in a laboratory.
6. How to measure pH in a given solution?
7. How to determine the pH is acidic in a given solution?
8. Why is pH important in our day-to-day life?
9. Give the reaction of bleaching.
10. Give the reaction of baking soda.

• The answers to the above questions are:

1. Acids are substances that provide a sour taste in water solution and have a pH range between 1 to 6. For example, citrus fruits have citrus which is acidic in nature.
2. Bases are hydroxides combined to groups 1 and 2 of the periodic table. For example, sodium hydroxide.
3. Salts are formed when the acid is treated with a base. Therefore, salt is a combination of cation and anion that results in neutralization or in other terms no charge.
4. 2NaOH + Zn → Na₂ZnO₂ + H₂ is a reaction that determines the interaction between the base(NaOH) and metal(Zn).
5. Acids like H₂SO₄, HCl, HNO₃. Bases like NaOH, KOH, LiOH, etc.
6. We measure pH using pH paper or pH meter.
7. When a pH paper is placed in a solution, and the color changes to a range between 1 to 6, it is considered acidic.
8. pH is important for digestion as it helps in protecting our body from diseases. Saliva, HCl in the stomach protects e the body from encountering various diseases.
9. Bleaching: Ca(OH)₂ + Cl₂ → CaCOl₂ + H₂O
10. Baking soda: NaCl +  H₂O + CO₂ + NH₃ → NH₄Cl + NaHCO₃