Acids, Bases and Salts: Class 7 Science Q&A · Page 2
34 free answers on Acids, Bases and Salts (Science) for Class 7 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- ScienceClass 7CBSE
Products of a neutralisation reaction are always (a) an acid and a base. (b) an acid and a salt. (c) salt and water. (d) a salt and a base.
Soln: The answer is (c) salt and water.
- ScienceClass 7CBSE
The correct way of making a solution of acid in water is to (a) add water to acid. (b) add acid to water. (c) mix acid and water simultaneously. (d) add water to acid in a shallow container.
Soln: The answer is (b) add acid to water. Explanation: If we add water to acid, it will be an exothermic reaction which will produce a lot of heat which may lead to an explosion. Hence, water should be added to the acid.
- ScienceClass 7CBSE
Consider the following statements: (a) Both acids and bases change colour of all indicators. (b) If an indicator gives a colour change with an acid, it does not give a change with a base. (c) If an indicator changes colour with a base, it does not change colour with an acid. (d) Change of colour in an acid and a base depends on the type of the indicator. Which of these statements are correct? (i) All four (ii) a and d (iii) b, c and d (iv) only d
Solution: (iv) Only d is correct Important topics covered in NCERT Solutions for Class 7 Chapter 5 Acids, Bases and Salts Section Number Topic 1 Acids and Bases 2 Natural Indicators around Us 3
- ScienceClass 7CBSE
Blue litmus paper is dipped in a solution. It remains blue. What is the nature of the solution? Explain.
Solution: The above solution may be neutral or basic in nature as both will not change the colour of the blue litmus paper.
- ScienceClass 7CBSE
Three liquids are given to you. One is hydrochloric acid, another is sodium hydroxide, and the 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. <l
- ScienceClass 7CBSE
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 aquati
- ScienceClass 7CBSE
Dorji has a few bottles of soft drinks in his restaurant. But, unfortunately, these are not labelled. He has to serve the drinks on the demand of customers. One customer wants an acidic drink, another wants a basic drink, and the third one wants a 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; the acidic solution is sour in taste, the 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 the soft drinks. 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
- ScienceClass 7CBSE
Mark ‘T’ if the statement is true and ‘F’ if it is false. (i) Nitric acid turns 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
- ScienceClass 7CBSE
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
- ScienceClass 7CBSE
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.
- ScienceClass 7CBSE
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.
- ScienceClass 7CBSE
Ammonia is found in many household products, such as window cleaners. It turns red litmus blue. What is its nature?
Solution: The answer is it is basic in nature.
- ScienceClass 7CBSE
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 </
- ScienceClass 7All
What is neutralisation reaction give two examples?
A neutralization reaction is a chemical reaction between an acid and a base that results in the formation of water and a salt. The reaction involves the transfer of protons (H⁺ ions) from the acid to the base, leading to the formation of water and an ionic compound known as a salt. The general form of a neutralization reaction is: acid+base→salt+wateracid+base→salt+water Here are two examples of neutralization reactions: 1. Hydrochloric Acid and Sodium Hydroxide: Hydrochloric acid (