NCERT Chapter 2 Science Class 10 Addition question solution || Acid, Base and Salt solution class 10 || Chemistry || Science ||

-
                                 Page 18:
 Ques 1: You have been provided with 3 test tubes. One of them contains distilled  water and the other 2 contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the  contents of each test tube? 

Ans 1: If the colour of red litmus paper gets changed to blue, then it is a base and if there  is no colour change, then it is either acidic or neutral. Thus, basic solution can be  easily identified. Let us mark the three test tubes as A, B, and C. A drop of the solution in A is put  on the red litmus paper. Same is repeated with solution B and C. If either of them changes colour to blue, then it is basic. Therefore, out of three, one is eliminated.  Out of the remaining two, any one can be acidic or neutral. Now a drop of basic  solution is mixed with a drop of each of the remaining two solutions separately and then the nature of the drops of the mixtures is checked. If the colour of red litmus turns blue, then the second solution is neutral and if there is no change in colour, then the second solution is acidic. This is because acidic and basic solutions neutralise each other. Hence, we can distinguish between the three types of solutions.

                                  Page 22:
 Ques 1: Why should curd and sour substances not be kept in brass and copper vessels?

Ans 1: Curd and other sour substances contain acids. Therefore, when they are kept in brass and copper vessels, the metal reacts with the acid to liberate hydrogen gas and harmful products, thereby spoiling the food.

Metal + Acid → Salt + Hydrogen gas

     Cu + H Cl → Cu Cl 2 + H 2 ↑

Ques 2: Which gas is usually liberated when an acid reacts with a metal? Illustrate with an example. How will you test for the presence of this gas? 

Ans 2: Hydrogen gas is usually liberated when an acid reacts with a metal. 

Take few pieces of zinc granules and add 5 ml of dilute H 2 SO 4. Shake it and pass  the gas produced into a soap solution. The bubbles of the soap solution are formed. These soap bubbles contain hydrogen gas.

        Z n + 2 H 2 SO 4 → Z n SO 4 + H 2 ↑

Ques 3: Metal compound A reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride.

Ans 3: C a CO 3 + 2 H Cl → C a Cl 2 + CO 2 + H 2 O

                             Page 25:

Ques 1: Why do HCl, H NO 3, etc., show acidic characters in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character? 

Ans 1: The dissociation of HCl or H NO 3 to form hydrogen ions always occurs in the presence of water. Hydrogen ions (H+) combine with H2O to form hydronium ions (H 3 O+) . 

Ques 2: Why does an aqueous solution of an acid conduct electricity? 

Ans 2: Acids dissociate in aqueous solutions to form ions. These ions are responsible for conduction of electricity. 

Ques 3: Why does dry HCl gas not change the colour of the dry litmus paper? 

Ans 3: Colour of the litmus paper is changed by the hydrogen ions. Dry HCl gas does not contain H+ ions. It is only in the aqueous solution that an acid dissociates to give ions. Since in this case, neither HCl is in the aqueous form nor the litmus paper is wet, therefore, the colour of the litmus paper does not change. 

Ques 4: While diluting an acid, why is it recommended that the acid should be added to  water and not water to the acid? 

Ans 4: The process of dissolving an acid or a base in water is a highly exothermic one. Care must be taken while mixing concentrated nitric acid or sulphuric acid with water. The acid must always be added slowly to water with constant stirring. If water is added to a concentrated acid, the heat generated may cause the mixture to splash out and cause burns. The glass container may also break due to excessive local heating 

Ques 5: How is the concentration of hydronium ions (H 3 O+) affected when a solution of an acid is diluted? 

Ans 5: When an acid is diluted, the concentration of hydronium ions (H 3 O+ ) per unit volume decreases. This means that the strength of the acid decreases. 

Ques 6: How is the concentration of hydroxide ions (OH–) affected when excess base is  dissolved in a solution of sodium hydroxide? 

Ans 6: The concentration of hydroxide ions (OH−) would increase when excess base is dissolved in a solution of sodium hydroxide.

                                  Page 28:

Ques 1: You have two solutions, A and B. The pH of solution A is 6 and pH of solution  B is 8. Which solution has more hydrogen ion concentration? Which of this is acidic and which one is basic? 

Ans 1: A pH value of less than 7 indicates an acidic solution, while greater than 7 indicates a basic solution. Therefore, the solution with pH = 6 is acidic and has more hydrogen ion concentration than the solution of pH = 8 which is basic. 

Ques 2: What effect does the concentration of H+  ions have on the nature of the solution? 

Ans 2: Concentration of H+ can have a varied effect on the nature of the solution. With an increase in H+ ion concentration, the solution becomes more acidic, while a decrease of H+ ion causes an increase in the basic city of the solution. 

Ques 3: Do basic solutions also have H+ ions? If yes, then why are these basic? 

Ans 3: Yes, basic solution also has H+ ions. However, their concentration is less as  compared to the concentration of OH− ions that makes the solution basic.

Ques 4: Under what soil condition do you think a farmer would treat the soil of his fields with quick lime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate)? 

Ans 4: If the soil is acidic and improper for cultivation, then to increase the basic city of  soil, the farmer would treat the soil with quick lime or slaked lime or chalk.

                                  Page 33:

Ques 1: What is the common name of the compound (calcium oxychloride) C a O Cl 2? 

Ans 1: The common name of the compound C a O Cl 2 is bleaching powder. 

Ques 2: Name the substance which on treatment with chlorine yields bleaching powder. 

Ans 2: Calcium hydroxide [C a(OH)2], on treatment with chlorine Cl 2, yields bleaching  powder. 

Ques 3: Name the sodium compound which is used for softening hard water. 

Ans 3: Washing soda (Na2CO3.10H2O) is used for softening hard water. 

Ques 4: What will happen if a solution of sodium hydro carbonate is heated? 

Ans 4: When a solution of sodium hydro carbonate is heated, sodium carbonate and water are formed with the evolution of carbon dioxide gas.

Ques 5: Write an equation to show the reaction between Plaster of Paris and water. 

Ans 5: Plaster of Paris is a white powder and on mixing with water, it changes to gypsum giving a hard solid mass.

Comments

Post a Comment

Popular posts from this blog

Diagonal Relationship between Beryllium and Aluminium || Relation between Beryllium and Aluminium

-
  Diagonal Relationship between Beryllium and Aluminium The ionic radius of Beryllium (Be 2+) is estimated to be nearly 31 pm; the charge/radius ratio Or e/m ratio is nearly the same as that of the Al 3+ ion. Hence beryllium resembles aluminium in these ways. Some of the similarities are given below: » Like Aluminium, Beryllium(be) is not readily attacked by acids H+ donor because of the formation of an oxide film on the surface of the metal by reacting with oxygen, i.e. they are rendered passive by nitric acid. » Beryllium hydroxide[[Be(OH)4]2] dissolves in excess of alkali to give a beryllate ion, [ Be(OH)4]2– just as aluminium hydroxide[Al(OH)3] gives aluminate ion, [Al(OH)4] » The chlorides of metals beryllium and aluminium have Cl– bridged chloride structure in vapour phase. Both the chlorides are soluble in organic solvents and are strong as Lewis acids They are used as Friedel Craft catalysts. » Beryllium(Be) and aluminium(Al) ions have strong tendency to form complexes, (BeF4)2
Read more

KVS CBSE Worksheets CHAPTER 1 Electric Charges and Fields Class 12

-
Image
                      SECTION A CONCEPTUAL AND APPLICATION TYPE QUESTIONS  1 Is the force acting between two point charges q1 and q2 kept at some distance apart in air attractive or repulsive when i) q1 q2 > 0 ii) q1 q2 < 0 ? 1 (2007)  2 If the distance between two equal point charges is doubled and their individual charges are also doubled ,what would happen to the force between them ? 1(2014)  3 Do the electrostatic field lines form closed loops? 1(2014)  4 A hollow metal sphere of radius 5cm is charged such that the potential on its is 10V. What is the electric field at the center of the sphere? 1(2011)  5 What is meant by the statement that   “the electric field of a point charge has spherical symmetry whereas electric field due to an electric dipole is cylindrically symmetrical’’ ? 1(1996)  6 Why is it difficult to perform electrostatic experiments on a humid day? 1  7 The distance of the field point on the equatorial plane of a small electric dipole , is halved. By wha
Read more

S-Block Elements || S-block element class 11 chapter 8 || Group 1A, 2A elements || S block elements chapter 8 notes class 11 || Chemistry ||

-
Image
                    INTRODUCTION : The s- block elements of the periodic table are those in which the last electron enters  into the outermost s-orbital. As the s-orbital can accommodate only two electrons, in two group (1 & 2) belong to the s-block of the periodic table. Group 1 of the periodic table consists of the elements : lithium (L i), sodium (Na), potassium (K), rubidium (R b), caesium (C s) and francium (F r). They are collectively known as alkali metals. These are called because they forms hydroxides on reaction with water which are strongly alkaline in nature. The elements of Group 2nd include beryllium (Be), magnesium (Mg), calcium (C a), strontium (S r), barium (B a) and radium (Ra). These elements with the exception of Beryllium are commonly known as the alkaline earth metals. These are so called because their oxide and hydroxide are alkaline in nature and these metal oxides are found in the earth’s crust . The general electronic configuration of s- block element is
Read more

Electric Charges and Fields || Electrostatics Notes || Physics || Class 12 || Chapter 1 Notes Class 12 ||

-
Image
                            Charge Charge is that property of an object by virtue of which it apply electrostatic force of interaction on other objects. Charges are of two types (i) Positive charge (+ve)  (ii) Negative charge (-ve)  Like charges repel and unlike charges attract each other.               Quantization of Charge Charge on any object can be an integer multiple of a smallest charge (e).                     Q = ± n e where, n = 1, 2, 3,……. and e = 1.6 * 10-19 C.                   Conservation of Charge Charge can neither be created nor be destroyed. but can be transferral from one object to another object. Recently a new particle has been discovered called ‘Quark’. It contains charge ± e / 3, ± 2e / 3. [The protons and neutrons are combination of other entities called quarks, which have charges 1 / 3 e. However, isolated quarks have not been observed, so, quantum of charge is still e. ]         Coulomb’s Law of Electrostatics Electrostatic force of interaction acting betwee
Read more

Diwali 2020 || Deepawali 2020 || Happy diwali || Festival of lights || 2020 ||

-
Image
                            Diwali Diwali is the festival of lights. Diwali is one of the most popular festivals of Hindus all over the world which is celebrated with great excitement , happiness and delight. Kids have a great time on Diwali as they get an opportunity to share their joyful experiences about the festival. Youngsters usually love this festival as it brings a lot of happiness and delightful moments for everyone. They get to meet their family, friends and relatives and share greetings and gifts with their loved ones. Diwali is also popularly known as “Deepawali” is one of the most celebrated festivals of Hindus residing in India or across the world. Diwali is celebrated with great fervour and enthusiasm by people throughout the world. Although it’s considered as a Hindu festival, but people from different communities celebrate the bright festival by bursting crackers and fireworks. According to Hindu mythology, Diwali is a festival which commemorates the return of Lord Ram
Read more