Class 10th Science Ch-2 Ncert Exemplar Question Answers. If you’re here to solve the Ncert Exemplar of the chapter 2 Acid Bases and Salts then I can understand that now you’re fully prepared.
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Multiple Choice Questions:- [Class 10th Science Ch-2 Ncert Exemplar Question Answers]
1. What happens when a solution of an acid is mixed with a solution of a base in a test tube?
(i) The temperature of the solution increases
(ii) The temperature of the solution decreases
(iii) The temperature of the solution remains the same
(iv) Salt formation takes place
- (i) only (b)
- (i) and (iii)
- (ii) and (iii)
- (i) and (iv)
Ans:- (4). (i) and (iv)
Explanation:- When an Acid Reacts with Base Rise in Temepratere takes place because it is a type of Exothermic Reaction and Acid + base —> Salt + water.
2. An aqueous solution turns red litmus solution blue. Excess addition of which of the following solution would reverse the change?
(a) Baking powder
(c) Ammonium hydroxide solution
(d) Hydrochloric acid
Ans:- (d) Hydrochloric acid
Explanation:- The color of Litmus paper was changed from Red to Blue means litmus paper was treated with any Basic Solution. And the change can be Reverse by adding hydrochloric acid Because it will neutralize the Basic effect and the litmus paper will again change to Red.
3. During the preparation of hydrogen chloride gas on a humid day, the gas is usually passed through the guard tube containing calcium chloride. The role of calcium chloride taken in the guard tube is to
(a) absorb the evolved gas
(b) moisten the gas
(c) absorb moisture from the gas
(d) absorb Cl– ions from the evolved gas
Ans:- (c). To Absorb the moisture from the Gas.
Explanation:- Calcium is used as a good dehydrating agent. It has the property to absorb moisture.
4. Which of the following salts does not contain water of crystallisation?
(a) Blue vitriol
(b) Baking soda
(c) Washing soda
Ans:- (b). Baking Soda (NaHCO₃)
5. Sodium carbonate is a basic salt because it is a salt of
(a) strong acid and strong base
(b) weak acid and weak base
(c) strong acid and weak base
(d) weak acid and strong base
Ans:- (d) weak acid and strong base, Because when weak Carbonic acid (H2CO3) and Strong base Sodium hydroxide(NaOH) reacts together then they form Na2CO3 (Sodium Carbonate).
6. Calcium phosphate is present in tooth enamel. Its nature is
Ans:- (a) basic, Calcium Phosphate is Basic in Nature.
7. A sample of soil is mixed with water and allowed to settle. The clear supernatant solution turns the pH paper yellowish-orange. Which of the following would change the colour of this pH paper to greenish-blue?
(a) Lemon juice
(c) Common salt
(d) An antacid
Ans:- (d) An antacid
8. Which of the following gives the correct increasing order of acidic strength
- Water < Acetic acid < Hydrochloric acid
- Water < Hydrochloric acid< Acetic acid
- Acetic acid< Water < Hydrochloric acid
- Hydrochloric acid< Water<Acetic acid
Ans:- (1). Water < Acetic acid < Hydrochloric acid
Water is neutral in nature with pH valur of 7. Acetic acid is an organic acid which is weak in nature with pH value of 4.7, and Hydrochloric acid is a strong acid with pH value of 3.01.
9. If a few drops of a concentrated acid accidentally spills over the hand of a student, what should be done?
(a) Wash the hand with saline solution
(b) Wash the hand immediately with plenty of water and apply a paste of sodium hydrogen carbonate
(c) After washing with plenty of water apply a solution of sodium hydroxide on the hand
(d) Neutralise the acid with a strong alkali
Ans:- (b) Wash the hand immediately with plenty of water and apply a paste of sodium hydrogen carbonate. Because, Washing hand with water will reduce the Concentration of Acid. And after that Apply the paste of Sodium Hydrogen, that will neutrilise the effect of Acid.
10. Sodium hydrogencarbonate when added to acetic acid evolves a gas. Which of the following statements are true about the gas evolved?
(i) It turns lime water milky
(ii) It extinguishes a burning splinter
(iii) It dissolves in a solution of sodium hydroxide
(iv) It has a pungent odour
(a) (i) and (ii)
(b) (i), (ii) and (iii)
(c) (ii), (iii) and (iv)
(d) (i) and (iv)
Ans:- (a) (i) and (ii)
Reaction between Sodium hydrogen carbonate (NaHCO3) and acetic acid (CH3COOH) lead to evolution of carbon-di-oxide gas. CO2 turns the lime water (CaO) milky and helps in extinguishing a burning splinter.
11. Common salt besides being used in kitchen can also be used as the raw material for making
(i) washing soda
(ii) bleaching powder
(iii) baking soda
(iv) slaked lime
(a) (i) and (ii)
(b) (i), (ii) and (iv)
(c) (i) and (iii)
(d) (i), (iii) and (iv)
Ans:- (a) (i) and (ii)
12. One of the constituents of baking powder is sodium hydrogencarbonate, the other constituent is
(a) hydrochloric acid
(b) tartaric acid
(c) acetic acid
(d) sulphuric acid
Ans:- (b) tartaric acid.
13. To protect tooth decay we are advised to brush our teeth regularly. The nature of the tooth paste commonly used is
Ans:- (c) Basic.
14. Which of the following statements is correct about an aqueous solution of an acid and of a base?
(i) Higher the pH, stronger the acid
(ii) Higher the pH, weaker the acid
(iii) Lower the pH, stronger the base
(iv) Lower the pH, weaker the base
(a) (i) and (iii)
(b) (ii) and (iii)
(c) (i) and (iv)
(d) (ii) and (iv)
Ans:- (d) (ii) and (iv)
15. The pH of the gastric juices released during digestion is
(a) less than 7
(b) more than 7
(c) equal to 7
(d) equal to 0
Ans:- (a) less than 7
16. Which of the following phenomena occur, when a small amount of acid is added to water?
(iv) Salt formation
(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii) and (iii)
(d) (ii) and (iv)
Ans:- (b) (i) and (iii).
17. Which one of the following can be used as an acid–base indicator by a visually impared student?
(c) Vanilla essence
(d) Petunia leaves
Ans:- (c) Vanilla essence
18. Which of the following substance will not give carbon dioxide on treatment with dilute acid?
(c) Baking soda
Ans:- (d) Lime
19. Which of the following is acidic in nature?
(a) Lime juice
(b) Human blood
(c) Lime water
Ans:- (a). Lime Juice.
21. Which of the following is used for dissolution of gold?
(a) Hydrochloric acid
(b) Sulphuric acid
(c) Nitric acid
(d) Aqua regia
Ans:- (d) Aqua regia
22. Which of the following is not a mineral acid?
(a) Hydrochloric acid
(b) Citric acid
(c) Sulphuric acid
(d) Nitric acid
Ans:- (b) Citric acid
23. Which among the following is not a base?
(d) C2H5 OH
Ans:- (d) C2H5 OH
24. Which of the following statements is not correct?
(a) All metal carbonates react with acid to give a salt, water and carbon dioxide
(b) All metal oxides react with water to give salt and acid
(c) Some metals react with acids to give salt and hydrogen
(d) Some non metal oxides react with water to form an acid
Ans:- (b) All metal oxides react with water to give salt and acid
Short Answer Questions [Class 10th Science Ch-2 Ncert Exemplar Question Answers]
33. What will be the action of the following substances on litmus paper? Dry HCl gas, Moistened NH3 gas, Lemon juice, Carbonated soft drink, Curd, Soap solution.
Effect of Dry HCl gas on Litmus Paper:- No effect
Effect of Moistened NH3 gas Litmus Paper:- litmus paper will turn from Red color to blue color
Effect of Lemon juice on Litmus Paper:- litmus paper will turn to red color
Effect of Carbonated soft drink on Litmus paper:- Turns litmus paper to blue color.
Effect of Curd on Litmus Paper- litmus paper will turn to red color
Effect of Soap solution on Litmus Paper:- Litmus paper to blue color
34. Name the acid present in ant sting and give its chemical formula. Also, give the common method to get relief from the discomfort caused by the ant sting.
Ans:- Methanoic acid is Present in Ant Sting. The chemical formula of methanoic acid is HCOOH. If we rub baking soda (NaHCO₃) on the affected area it can give relief from the discomfort caused by ant sting.
35. What happens when nitric acid is added to eggshell?
Ans:- Egg Shells are made up of Calcium Carbonate (CaCO3). And when Eggshells react with the HNO3 (Nitric acid) then Calcium Nitrate (Ca(NO3)2) and carbon-di-oxide gas (CO2). HNO3 is considered one of the strongest acids, and when it reacts with the Eggshells then a lot of energy released in the form of heat.
37. How would you distinguish between baking powder and washing soda by heating?
Ans:- We can Distinguish between the baking powder and washing soda by the following properties:- 1. The formula of baking Powder is NaHCO3, whereas the formula of washing soda is Na2CO3.10H2O.
2. Also when we heat Baking Powder then CO2 gas releases that help in making cakes and bakery products softer, whereas when we heat washing soda then no gas CO2 gas released.
You can also test the CO2 gas by passing it through the lime water. When we pass CO2 through the lime water then it turns Milky.
41. What are strong and weak acids? In the following list of acids, separate strong acids from weak acids. Hydrochloric acid, citric acid, acetic acid, nitric acid, formic acid, sulphuric acid.
Ans:- Strong Acids:- These acids are the acids that completely ionized in Aqueous solutio*n. Weak acids:- these acids are the acids that do not completely ionized in the aqueous solution.
2. Here HCl (Hydrochloric Acid):- It is a strong synthetic Acid.
Citric Acid:- this is a weak natural acid. found in lemon.
acetic Acid:- this is also a weak acid found in vinegar.
Nitric Acid:- This is a strong synthetic Acid.
Formic acid:- This is a natural weak acid found in the ant or bee sting. Also, known as Methanoic Acid.
Sulphuric acid:- This acid is a strong acid and this is also known as King of all the Acids.
42. When zinc metal is treated with a dilute solution of a strong acid, a gas is evolved, which is utilized in the hydrogenation of oil. Name the gas evolved. Write the chemical equation of the reaction involved and also write a test to detect the gas formed.
Ans:- when Zinc so react with the dilute acid then H2 (Hydrogen) gas releases which are also used in the process of Hydrogeniatiojn (ch-4) topic.
In this Reaction, hydrogen gas will evolved. Zn+HCl(dil.) —-> ZnCl2 + H2.
The h2 gas can be tested by the soap water test. In which when we burn the hydrogen gas then it burst with a pop sound.
Long Answer Questions [Class 10th Science Ch-2 Ncert Exemplar Question Answers]
Ans:- The Reaction takes place will be more vigorous and fast. Mest the rate of reaction will increase.
(ii). No, any extra-ordinary effect will appear. The about same amount of H2 gas will release.
(iii). Then no hydrogen gas will release because Cu doesn’t react with the dil. Hydrochloric acid.
(iv). In this case, H2 gas will release but the salt form will be Sodium Zincate (Na2ZnO2). NaOH + Zn —-> Na2ZnO2 + H2
44. For making a cake, baking powder is taken. If at home, your mother uses baking soda instead of baking powder in cake,
(a) how will it affect the taste of the cake and why?
(b) how can baking soda be converted into baking powder?
(c) what is the role of tartaric acid added to baking soda?
Ans:- The cake that will be formed will be bitter in taste. Because on heating Baking soda sodium carbonate will form.
Here is the reaction that will take place when we heat baking powder:- 2NaHCO3 +Heat Na2Co3+CO2+H2O.
(ii). baking soda can be converted into baking powder by adding a weak edible acid that is tartaric acid.
(iii). When we dissolve tartaric acid in the water, then Hydrogen ions released. Then Hydrogen ions react with Sodium Carbonate (Na2CO3) to produce carbon dioxide (CO2), which makes the cake fluffy.
45. A metal carbonate X on reacting with acid gives a gas which when passed through a solution Y gives the carbonate back. On the other hand, a gas G that is obtained at the anode during electrolysis of brine is passed on dry Y, and it gives a compound Z, used for disinfecting drinking water. Identity X, Y, G, and Z.
Ans:- Here the Metal X is Calcium and when Calcium Carbonate reacts with the HCl then it produces CO2 (Carbon dioxide).
And when CO2 gas will pass through the lime water that is CaO it will give the metal Carbonate back that is Calcium Carbonate.
So here Y is lime water.
And Z is chlorine. Because when we pass chlorine gas on dry lime water, it gives bleaching powder (CaOCl2) which is used for disinfecting water.
46. A dry pellet of a common base B, when kept in the open absorbs moisture and turns sticky. The compound is also a by-product of the chloralkali process. Identify B. What type of reaction occurs when B is treated with an acidic oxide? Write a balanced chemical equation for one such solution.
A compound that is a byproduct of the chloralkali process is NaOH. Hence compound B is NaOH.
When NaOH is treated with acidic oxide neutralization process occurs. For example, If NaOH is treated with carbon-di-oxide, it gives Sodium carbonate.
2NaOH+ CO2 →Na2CO3+ H2O
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