CBSE Class 10 Science Acids Bases And Salts Worksheet Set B

 ACIDS BASES AND SALTS

Question. Ionic theory of acid and bases was proposed by -
(A) Lowry
(B) Bronsted
(C) Lewis
(D) Arrhenius
Answer. D

Question. The conjugate acid of NH₂^– is -
(A) NH₃
(B) NH₂OH
(C) NH₄⁺
(D) ClO₄^–
Answer. A

Question. According to Lewis concept, the acid is -
(A) proton acceptor.
(B) electron pair donor.
(C) electron pair acceptor.
(D) proton donor.
Answer. C

Question. Which of the following could act as a Lewis acid but not Bronsted acid ?
(A) HCl
(B) H₂SO₄
(C) HSO₃^–
(D) SO₃
Answer. D

Question. Which of the following ion is a Lewis base ?
(A) CH₃⁺
(B) H₃O ⁺
(C) NH₂^–
(D) NH₄⁺
Answer. C

Question. Which of the following represents acid-base pair for the equilibrium reaction ?
HCl + H₂O H₃O⁺ + Cl^–
(A) HCl, H₂O
(B) HCl, H₃O⁺
(C) HCl, Cl^–
(D) Cl^–, H₂O
Answer. C

Question. The reaction of water with ammonia is given by the following equation , in this reaction water acts as :
H₂O + NH₃ NH₄⁺ + OH^–
(A) neutral
(B) base
(C) acid
(D) both acid and base
Answer. C

Question. The salt whose aqueous solution will have no effect on ether red litmus or blue litmus is -
(A) potassium sulphate
(B) sodium carbonate
(C) ammonium sulphate
(D) sodium acetate
Answer. A

Question. Which of the following indicators is colourless in acidic medium:
(A) methyl orange
(B) turmeric powder
(C) litmus
(D) phenolphthalien
Answer. D

Question. The chemical composition of plaster of paris is : 
(A) CaSO₄ . 2H₂O
(B) CaSO₄. H₂O
(C) CaSO₄. ½ H₂O
(D) CaSO₄. 3H₂O
Answer. C

Question. The pair of the solutions which have pH value less than 7, is - 
(A) solution of washing soda and solution of vinegar
(B) solution of soap and solution of washing soda
(C) solution of copper sulphate and solution of washing soda
(D) solution of copper sulphate and vinegar
Answer. D

Question. Salt made of non-metallic elements only is :
(A) NaCl
(B) NH₄Cl
(C) AlN
(D) MgCl₂
Answer. B

Question. pH of soda water is : 
(A) 7
(B) < 7
(C) > 7
(D) 0
Answer. B

Question. Common name of Sodium Carbonate is-
(A) Baking Soda
(B) Washing Soda
(C) Bleaching Powder
(D) Quick Lime
Answer. B

Question. What is the Molecular formula of Gypsum ? 
(A) CaCO₃
(B) CaSO₄ . 2H₂O
(C) CaO
(D) Ca(OH)₂
Answer. B

Question. About (i) CsOH, (ii) KOH, (iii) Be (OH)₂ the correct statement is : 
(A) All are bases
(B) (ii) and (iii) are bases, (i) is acidic
(C) (i) is acidic, (ii) is basic , (iii) is amphoteric
(D) (ii) and (iii) are basic, (i) is amphoteric
Answer. A

Question. Sodium Bicarbonate on decomposition forms :
(A) NaHCO₃
(B) Na₂CO₃
(C) Na₂CO₃. H₂O
(D) Na₂CO₃. 10H₂O
Answer. B

Question. Salt of strong acid and weak base have pH value :
(A) Less than 7
(B) More than 7
(C) Only 7
(D) Only 14
Answer. A

Question. Electric current is passed through a concentrated aqueous solution of sodium chloride by means of a battery. After disconnecting the circuit the solution thus obtained is divided into two equal parts by volume. In one part phenolphthalein and in another part methyl orange indicator was added. The colour of the solutions will be respectively -
(A) Pink and Red
(B) Colourless and Yellow
(C) Pink and Yellow
(D) Colourless and Red
Answer. C

Question. An acid, obtained by destructive distillation of wood , which in turn give acetic acid is ............
(A) Oxalic acid
(B) Pyroligneous acid
(C) Chloro acetic acid
(D) Citric acid
Answer. B

Question. The colour of phenolphthalein in acidic medium is-
(a) Yellow
(b) Pink
(c) Colourless
(d) Blue
Answer. C

Question. The gas which burns with a pop sound –
(a) H₂
(b) CO₂
(c) O₂
(d) CH₄
Answer. A

Question. Milkiness of limewater disappear when excess CO₂ is passed due to the formation of-
(a) Calcium hydroxide
(b) Calcium chloride
(c) Calcium bicarbonate
(d) Calcium carbonate
Answer. C

Question. The acid present in tomato is-
(a) Lactic acid
(b) Oxalic acid
(c) Tartaric acid
(d) Methanoic acid
Answer. B

Question. The common name for the substance used as antacid-
(a) Washing soda
(b) Plaster of Paris
(c) Bleaching powder
(d) Baking soda
Answer. D

Question. Calcium carbonate reacts with hydrochloric acid to form X, Y ,Z. What areX, Y, Z ? 
(a) X:Ca(OH)₂,Y:H₂O,Z:CO₂
(b) X:CaCl₂,Y:H₂O, Z:CO₂
(c) X:Ca(OH)₂,Y:H₂O,Z:H₂
(d) X:CaCl₂,Y:H₂O,Z:H₂
Answer. B

Question. When you clean a metal vessel with tamarind the reaction taking place is:
Metaloxide+X--------→ Salt+Water. What is X here?
(a) Acid
(b) Base
(c) Hydrogen
(d) Carbon dioxide
Answer. A

Question. Brine is an
(a) aqueous solution of sodium hydroxide
(b) aqueous solution of sodium carbonate
(c) aqueous solution of sodium chloride
(d) aqueous solution of sodium bicarbonate
Answer. C

Question. Sodium carbonate is a basic salt because it is a salt of a
(a) strong acid and strong base
(b) weak acid and weak base
(c) strong acid and weak base
(d) weak acid and strong base
Answer. D

Question. Nettle sting is a natural source of which acid?
(a) Methanoic acid
(b) Lactic acid
(c) Citric acid
(d) Tartaric acid
Answer. A

Question. Tooth enamel is made up of
(a) calcium phosphate
(b) calcium carbonate
(c) calcium oxide
(d) potassium
Answer. A

Question. Rain is called acid rain when its:
(a) pH falls below 7
(b) pH falls below 6
(c) pH falls below 5.6
(d) pH is above 7
Answer. C

Question. Farmers neutralize the effect of Acidity on soil by adding
(a) Slaked Lime
(b) Gypsum
(c) Caustic Soda
(d) Baking Soda
Answer. A

Question. In which pH range does our body work to survive in the atmosphere?
(a) 5.5 to 8.5
(b) 7.0 to 7.8
(c) 2.3 to 7.0
(d) 7.5 to 12.5
Answer. B

Question. The pH of a solution is 7. How can you increase its pH?
(a) By adding a small amount of acid
(b) By adding a small amount of base.
(c) By adding a small amount of salt.
(d) By passing carbon dioxide gas through it.
Answer. B

Question. Which gas is evolved when acids react with metals?
(a) O₂
(b) CO₂
(c) H₂
(d) N₂
Answer. C

Question. Which of the following gives the correct increasing order of acidic strength?
(a) Water < Acetic acid < Hydrochloric acid
(b) Water < Hydrochloric acid < Acetic acid
(c) Acetic acid < Water < Hydrochloric acid
(d) Hydrochloric acid < Water < Acetic acid
Answer. A

Question. One of the constituents of baking powder is sodium hydrogen carbonate, the other constituent is
(a) hydrochloric acid
(b) tartaric acid
(c) acetic acid
(d) sulphuric acid
Answer. B

Question. The pH of three solutions X, Y and Z is 6, 4 and 8 respectively. Which of the following is the correct order of acidic strength?
(a) X > Y > Z
(b) Z > Y > X
(c) Y > X > Z
(d) Z > X > Y
Answer. C

Question. What is gastric acid present in the stomach composed of?
(a) Hydrochloric acid
(b) Sulphuric acid
(c) Nitric acid
(d) Lactic acid
Answer. A

ASSERTION AND REASON QUESTIONS:

DIRECTION: Each of these questions contains an Assertion followed by Reason. Read them carefully and answer the question on the basis of following options. You have to select the one that best describes the two statements.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true and R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.

Question. Assertion (A) : The acid must be added to water with constant stirring.
Reason(R) : Mixing of an acid with water decreases the concentration of H+ ions per unit volume.
Answer. B

Question. Assertion(A): Copper sulphate crystals are wet because it contains water of crystallization.
Reason(R): Water of crystallization is the fixed number of molecules of water present in one formula unit of salt.
Answer. D

Question. Assertion(A): The aqueous solution of glucose and alcohol do not show acidic character.
Reason(R ): Aqueous solution of glucose and alcohol do not give H+ ions .
Answer. A

Question. Assertion(A): Pure water is neither acidic nor basic.
Reason(R ): The pH of a solution is inversely proportional to the the concentration of H+ ions in it.
Answer. B

Question. Assertion(A): Weak acids have low electrical conductivity.
Reason(R ): Strong acids and weak acids have equal concentration of H+ ions in their solutions.
Answer. C

Question. The acid present in tomato is-
(a) Lactic acid
(b) Oxalic acid
(c) Tartaric acid
(d) Methanoic acid

Answer: B

Question. Rain is called acid rain when its:
(a) pH falls below 7
(b) pH falls below 6
(c) pH falls below 5.6
(d) pH is above 7

Answer: C

Question. Sodium carbonate is a basic salt because it is a salt of a
(a) strong acid and strong base
(b) weak acid and weak base
(c) strong acid and weak base
(d) weak acid and strong base

Answer: D

Question. One of the constituents of baking powder is sodium hydrogen carbonate, the other constituent is
(a) hydrochloric acid
(b) tartaric acid
(c) acetic acid
(d) sulphuric acid

Answer: B

Question. When you clean a metal vessel with tamarind the reaction taking place is:
Metaloxide + X--------→ Salt + Water. What is X here?
(a) Acid
(b) Base
(c) Hydrogen
(d) Carbon dioxide

Answer: A

Question. The pH of a solution is 7. How can you increase its pH?
(a) By adding a small amount of acid
(b) By adding a small amount of base.
(c) By adding a small amount of salt.
(d) By passing carbon dioxide gas through it.

Answer: B

Question. Which gas is evolved when acids react with metals?
(a) O₂
(b) CO₂
(c) H₂
(d) N₂

Answer: C

Question. Calcium carbonate reacts with hydrochloric acid to form X, Y ,Z. What areX, Y, Z ?
(a) X:Ca(OH)₂,Y:H₂O,Z:CO₂
(b) X:CaCl₂,Y:H₂O, Z:CO₂
(c) X:Ca(OH)₂,Y:H₂O,Z:H₂
(d) X:CaCl₂,Y:H₂O,Z:H₂

Answer: B

Question. What is gastric acid present in the stomach composed of?
(a) Hydrochloric acid
(b) Sulphuric acid
(c) Nitric acid
(d) Lactic acid

Answer: A

Question. Nettle sting is a natural source of which acid?
(a) Methanoic acid
(b) Lactic acid
(c) Citric acid
(d) Tartaric acid

Answer: A

CASE STUDY BASED QUESTIONS:

1. Read the following and answer the questions :
There are many substances which are used to detect the solutions as acidic or basic. They are called Acid-Base indicators. Depending upon the property of the indicator, we have
different groups of Acid-Base indicators. Some indicators show different colors in acidic or basic medium and some indicators give different odors in acidic and basic medium. These
indicators are either extracted from the plants or synthesized in the laboratory or industry.

Question. Which one of the following can be used as an acid-base indicator by visually impaired student?
(a) Turmeric
(b) Hibiscus
(c) Vanilla
(d) Litmus

Answer: C

Question. Select the incorrect option. 

Answer: B

Question. Which of the following are olfactory indicators?
(a) Onion Extract 
(b) Vanilla Extract
(c) Clove Oil
(d) All are correct

Answer: B

Question. Which of the following will turn red litmus blue?
(a) Amla juice
(b) Soft drink
(c) lemon juice
(d) Baking soda

Answer: D

Question. A solution turns blue litmus red, the pH of the solution is likely to be
(a) 6
(b) 7
(c) 8
(d) 9

Answer: A

2. Read the following and answer the questions :
Taj mahal, the seventh wonder of the world, is made of white stone. This white stone contains the same substance ‘A’ that is present in chalk powder and lime-stone. It is turning
yellow due to polluted air. If it is cleaned by an acidic cleaner, a gas ‘B’ is released, which
when passed through a solution ‘C’, forms the same substance which is present in the white
stone that was used to make Taj mahal.

Question. Solution C is-
(a) CaCl₂
(b) B. CaCO₃
(c) Ca(OH)₂
(d) CaSO₄

Answer: C

Question. The polluted air around Taj mahal leads to the following problem because of which it is getting Marble cancer:
(a) Global Warming
(b) Acid Rain
(c) Green House Effect
(d) All are correct

Answer: B

Question. What is the nature of the substance A?
(a) Acidic
(b) Basic
(c) Neutral
(d) None

Answer: B

Question. The substance A is-
(a) Ca3CO₂
(b) CaCO₃
(c) Ca(OH)₂
(d) CaSO₄

Answer: B

Question. Gas B is-
(a) Hydrogen
(b) Nitrogen
(c) Chlorine
(d) Carbon di oxide

Answer: D

3. Read the following and answer the questions :
A scale for measuring hydrogen ion concentration in a solution, called pH scale has been developed. The p in pH stands for ‘potenz’ in German, meaning power. On the pH scale we can measure pH from 0 to 14. pH should be thought of simply as a number which indicates the acidic or basic nature of a solution. Higher the hydronium ion concentration, lower is the Ph value.

Question. A basic solution could have a pH of-
(a) 3
(b) 5
(c) 7
(d) 9

Answer: B

Question. The table provides the pH of four solutions P, Q, R and S:

Which of the following correctly represents the solutions in increasing order of their hydronium ion concentration?
(a) P> Q>R >S
(b) P>S >Q >R
(c) S<Q <R <P
(d) S< P < Q<R

Answer: C

Question. If the pH of any solution is 13, then the color obtained on adding universal indicator to it will be:
(a) Red
(b) Orange
(c) Green
(d) Purple

Answer: D

Question. Which one of the following will have the highest hydrogen ion concentration?
(a) pH=1.1
(b) pH = 2.2
(c) pH =3.3
(d) pH =4.4

Answer: A

Question. How is the hydrogen ion concentration and pH related to each other?
(a) They are inversely proportional.
(b) They are directly proportional.
(c) They are equal.
(d) They have no relation.

Answer: D

4. Read the following and answer the questions :
The Ph value of any solution is a number which simply represents the acidity and basicity of that solution. The pH value of any solution is numerically equal to the logarithm of the inverse of the hydrogen ion(H⁺) concentration.

Question. The nature of toothpaste is:
(a) Neutral
(b) Acidic
(c) Basic
(d) Can be acidic or basic

Answer: C

Question. If a solution gives dark blue color and water is added to it, its color will become:
(a) Dark blue
(b) Red
(c) Light blue to green
(d) Purple

Answer: C

Question. Universal indicator strip gives green colur when put in our mouth before eating food. This indicates that:
(a) The pH of saliva is basic in nature
(b) The pH of saliva is near neutral
(c) Saliva is acidic in nature
(d) All are in correct

Answer: A

Question. The pH value for distilled water would be:
(a) 5
(b) 6
(c) 7
(d) 10

Answer: C

Question. Using above picture can you predict the colour of Ph paper when dipped in limejuice:
(a) Dark Red
(b) Light Orange
(c) Green
(d) Blue

Answer: D

5. Read the following and answer the questions :
Water of crystallization is the fixed number of water molecules present in one formula unit of a salt. Water of crystallization or water(s) of hydration are water molecules that are present inside crystals. Water is often incorporated in the formation of crystals from aqueous solutions. A salt with associated water of crystallization is known as a hydrate.

Question. The formula of Plaster of Paris is CaSO4. ½ H₂O, it is to be noted that half water molecule is shown to be attached as water of crystallization. This indicates that
(a) Only half water molecule is present in Calcium Sulphate crystal
(b) Two formula units of Calcium Sulphate share one molecule of water.
(c) Two formula units of calcium Sulphate share two molecules of water
(d) Two formula units of Calcium Sulphate share one and a half molecules of water.

Answer: B

Question. Given below are some chemicals. Select the one that have 7 molecules of water attached in hydrated form:
(a) Blue vitriol
(b) Green Vitriol
(c) POP
(d) Washing Soda

Answer: B

Question. When blue vitriol is heated its color changes from:
(a) White to Blue `
(b) Blue to White
(c) White to Green
(d) Blue to Green

Answer: B

Question. Which of the following salt does not contain water of crystallisation?
(a) Blue Vitriol
(b) Baking Soda
(c) Washing soda
(d) Gypsum

Answer: B

Question. The temperature at which Gypsum (CaSO₄. 2H₂O) into Plaster of Paris (CaSO₄.1/2 H₂O
(a) 373K
(b) 273K
(c) 374K
(d) 430K

Answer: A
 

Very Short Answers Type Questions

Question. A teacher provided acetic acid, water, lemon juice, aqueous solution of sodium hydrogen carbonate and sodium hydroxide to students in the school laboratory to determine the pH values of these substances using pH papers. One of the students reported the pH values of the given substances as 3, 12, 4, 8 and 14 respectively. Which one of these values is not correct ? Write its correct value stating the reason.
Answer : The value of pH for water is not correct. The correct value of pH of water is 7 because it has almost equal concentration of H+ and OH– due to which it is neutral.

Question. What is observed when a pinch of sodium hydrogen carbonate is added to 2 ml of acetic acid taken in a test tube ? Write chemical equation for the reaction involved in this case.
Answer : CO₂ gas is evolved with brisk effervescence when sodium hydrogen carbonate is added to acetic acid.
NaHCO₃       +        CH₃COOH CH₃COONa   + H₂O + CO₂
Sodium hydrogen    Acetic acid     Sodium
carobonate acetate

Question.Blue litmus solution is added to two test tubes A and B containing dilute HCl and NaOH solution respectively. In which test tube a colour change will be observed ? State the colour change and give its reason. 
Answer : Test tube A will show colour change because acids turn blue litmus to red. So the final colour of test tube would be red.

Question. What is observed when 2 ml of dilute hydrochloric acid is added to 1 g of sodium carbonate taken in a clean and dry test tube ? Write chemical equation for the reaction involved.
Answer : A brisk effervescence would be observed if HCl is
added to Na₂CO₃ due to the evolution of CO₂ gas.
Na₂ CO₃ + HCl → NaCl + H₂O + CO₂.

Question. A gas is liberated immediately with a brisk effervescence, when you add acetic acid to sodium hydrogen carbonate powder in a test tube. Name the gas and describe the test that confirms the identity of the gas. 
Answer :
CH₃COOH + NaHCO₃ → CH3COONa + CO₂ + H₂O
Gas evolved is CO₂. It is tested by passing CO₂ in lime water which turns milky due to formation of insoluble CaCO₃.
Ca(OH)₂ + CO₂ → CaCO₃↓ + H₂O

Question. Name one animal and one plant whose stings contain formic acid (or methanoic acid). 
Answer : Animal that contains formic acid–ant. Plant that contains formic acid–nettle plant.

Question. If someone is suffering from the problem of acidity after overeating, which of the following would you suggest as remedy ? Lemon juice, Vinegar, Baking soda solution. Give reason for your choice. 
Answer : Baking soda solution. The solution being basic in nature, it neutralises excess acid in the stomach.

Question.How is the neutralisation of a carbonate with an acid different from the neutralisation of an oxide or a hydroxide ? 
Answer : Neutralisation of a carbonate with an acid produces carbon dioxide gas but not with an oxide or hydroxide.

Question. Why do acids not show acidic behaviour in the absence of water ?
Answer : Acids do not show acidic behaviour in the absence of water because the dissociation of hydrogen ions from an acid occurs in the presence of water only. It is the hydrogen ions that are responsible for the acidic behaviour.

Question. On adding dilute hydrochloric acid to copper oxide powder, the solution formed is blue-green.
(a) Predict the new compound formed which imparts a blue-green colour to solution.
(b) Write a balanced chemical equation of the reaction which takes place.
(c) On the basis of the above reaction, what can you say about the nature of copper oxide ?
Answer :
(a) The new compound formed is Copper (II) chloride,CuCl₂.
(b) CuO(s) + 2HCl(aq) → CuCl₂(aq) + H₂O(l)
(c) Copper oxide is basic in nature.

Question. A substance X which is used as an antacid reacts with dilute hydrochloric acid to produce a gas Y which is used in one type of fire-extinguisher. Name the substance X and gas Y. Write a balanced equation for the chemical reaction which takes place.
Answer : Substance X is sodium hydrogen carbonate; gas Y is
carbon dioxide.
NaHCO₃ + HCl → NaCl + CO₂ + H₂O

Question. (a) Why is it wrong to treat a bee sting with vinegar ?
(b) Why is it wrong to treat a wasp sting with baking soda solution ?
Answer :
(a) Bee injects acid into the skin. Vinegar is acetic acid so it can’t be used to treat bee sting.
(b) Since baking soda is basic in nature so it can’t be used to treat wasp sting because wasp injects alkaline liquid into the skin.

Question. What happens when phenolphthalein is added to an acidic solution ?
Answer : There is no change in colour as it remains colourless.

Question. In the laboratory of a school, the sample of hard water is not available “to study the comparative cleaning capacity of a sample of soap in soft and hard water”.
Which salt from the laboratory can be added to tap water to make it hard ? In the experiment how is cleaning capacity of soap compared ?
Answer :
(a) Sulphate, chloride or hydrogen carbonate of calcium or magnesium can be added to tap water to make it hard.
(b) By adding equal amount of soap to water taken in two test tubes, shaking vigorously and comparing the length of lather or foam formed in each test tube. The cleaning capacity of soap is compared.

Short Answers Type Questions

Question. Complete and balance the following chemical equations : 
(i) NaOH(aq) + Zn(s) →
(ii) CaCO₃(s) + H₂O(l) + CO₂(g) →
(iii) HCl(aq) + H₂O(l) →
Answer :
(i) 2NaOH + Zn    550º C→    Na₂ZnO₂ + H₂
(ii) Calcium carbonate will react with water that is saturated with carbon dioxide to form the soluble calcium bicarbonate.
CaCO₃(s) + CO₂ (g) + H₂O (l) → Ca (HCO₃)₂(aq)
(iii) HCl + H₂O → H₃O+ + Cl–

Question. (a) While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid ?
(b) Dry hydrogen chloride gas does not change the colour of dry litmus paper why ? 
Answer :
(a) The process of mixing the concentrated acid with water is highly exothermic. So, when a concentrated acid is added to water then heat is easily absorbed by the large amount of water. Thus it is recommended to add acid to water and not water to the acid.
(b) Dry hydrogen chloried does not contain any hydrogen ions in it, so it does not show acidic behaviour and thus does not change the colour of dry litmus paper.

Question. How is sodium hydroxide manufactured in industries? Name the process. In this process a gas X is formed as by-product. This gas reacts with lime water to give a compound Y, which is used as a bleaching agent in the chemical industry. Identify X and Y and write the chemical equation of the reaction involved.
Answer : Sodium hydroxide is manufactured by the electrolysis of concentrated aqueous solution of sodium chloride.
                                      Electricity
2NaCl(aq.)   +   2H₂O(l)     →
                                    (Electrolysis)

Sodium chloride   Water
                          (Brine)
2NaOH(aq.)    +    Cl₂(g)      +   H₂(g)
Sodium hydroxide   Chloride     Hydrogen
(Caustic Soda)

The process of manufacture of sodium hydroxide by electrolysis process is called chlor-alkali process.
Gas X is chlorine gas and compound Y is calcium oxychloride (Bleaching powder)
Cl₂(g)    +    Ca(OH)₂  →  CaOCl₂ + H₂O
Chlorine    Lime water     Calcium
gas (X)                       oxychloride (Y)

Question. What would a student report nearly after 30 minutes of placing duly cleaned strips of aluminium, copper, iron and zinc in freshly prepared iron sulphate solution taken in four beakers ? 
Answer : Aluminium displaces the iron from iron sulphate and the colour of two solution changes from green to colourless.
No change takes place when copper strip is dipped in iron sulphate solution.
No change will be observed when iron strips are dipped in iron sulphate solution.
The colour of the solution changes from green to colourless when zinc is added to iron sulphate solution.

Question. Milkiness of limewater disappear when excess CO₂ is passed due to the formation of-
(a) Calcium hydroxide
(b) Calcium chloride
(c) Calcium bicarbonate
(d) Calcium carbonate

Answer: C

Question. Tooth enamel is made up of
(a) calcium phosphate
(b) calcium carbonate
(c) calcium oxide
(d) potassium

Answer: A

Question. The colour of phenolphthalein in acidic medium is-
(a) Yellow
(b) Pink
(c) Colourless
(d) Blue

Answer: C

Question. Farmers neutralize the effect of Acidity on soil by adding
(a) Slaked Lime
(b) Gypsum
(c) Caustic Soda
(d) Baking Soda

Answer: A

Question. Brine is an
(a) aqueous solution of sodium hydroxide
(b) aqueous solution of sodium carbonate
(c) aqueous solution of sodium chloride
(d) aqueous solution of sodium bicarbonate

Answer: C

Question. Which of the following gives the correct increasing order of acidic strength?
(a) Water < Acetic acid < Hydrochloric acid
(b) Water < Hydrochloric acid < Acetic acid
(c) Acetic acid < Water < Hydrochloric acid
(d) Hydrochloric acid < Water < Acetic acid

Answer: A

Question. The pH of three solutions X, Y and Z is 6, 4 and 8 respectively. Which of the following is the correct order of acidic strength?
(a) X > Y > Z
(b) Z > Y > X
(c) Y > X > Z
(d) Z > X > Y

Answer: C

Question. The gas which burns with a pop sound –
(a) H₂
(b) CO₂
(c) O₂
(d) CH₄

Answer: A

Question. In which pH range does our body work to survive in the atmosphere?
(a) 5.5 to 8.5
(b) 7.0 to 7.8
(c) 2.3 to 7.0
(d) 7.5 to 12.5

Answer: B

Question. The common name for the substance used as antacid-
(a) Washing soda
(b) Plaster of Paris
(c) Bleaching powder
(d) Baking soda

Answer: D

ASSERTION AND REASON QUESTIONS:

DIRECTION: Each of these questions contains an Assertion followed by Reason. Read them carefully and answer the question on the basis of following options. You have to select the one that best describes the two statements.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true and R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.

Question. Assertion(A): The aqueous solution of glucose and alcohol do not show acidic character.
Reason(R): Aqueous solution of glucose and alcohol do not give H⁺ ions.

Answer: A

Question. Assertion(A): Pure water is neither acidic nor basic.
Reason(R): The pH of a solution is inversely proportional to the the concentration of H⁺ ions in it.

Answer: B

Question. Assertion (A) : The acid must be added to water with constant stirring.
Reason(R) : Mixing of an acid with water decreases the concentration of H⁺ ions per unit volume.

Answer: B

Question. Assertion(A): Weak acids have low electrical conductivity.
Reason(R): Strong acids and weak acids have equal concentration of H⁺ ions in their solutions.

Answer: C

Question. Assertion(A): Copper sulphate crystals are wet because it contains water of crystallization.
Reason(R): Water of crystallization is the fixed number of molecules of water present in one formula unit of salt.

Answer: D

Very short answer type questions:

Question. What is the chemical name and chemical formula of baking soda?
Answer: Sodium Hydrogen Carbonate or Sodium bicarbonate. Its formula is NaHCO₃.

Question. Which bases are called alkalies? Give an example.
Answer: Water soluble bases are called alkalies. e.g.- NaOH

Question. Name an olfactory indicator?
Answer: Onion

Question. Name the gas evolved when dilute HCl reacts with sodium bi carbonate? How is it recognized?
Answer: The gas evolved is CO₂. When it is passed through lime water, it becomes milky.

Question. The pH of an aqueous solution decreases from 3 to 2. What will happen to the nature of the solution ?
Answer: The acidic character of the solution will further increases.

Short answer type questions:

Question. The oxide of a metal M was water soluble. When a blue litmus trip was dipped in this solution, it did not undergo any change in color .Predict the nature of the oxide.
Answer: The metal oxide (MO) is of basic in nature. It dissolves in water to from metal hydroxide as follow.
MO + H₂O-----→M(OH)₂
A blue litmus does not undergo any change in color in the basic medium.

Question. A doctor applied surgical bandages on the fractured bones of a patient after making it wet. What changes are likely to occur?
Answer: Surgical bandages are made from plaster of Paris. When applied on the fractured bones after making them wet , it changes into a hard mass called Gypsum.
CaSO₄.1/2 H₂O + 3/2 H₂O-------→ CaSO₄.2H₂O

Question. Fresh milk has pH of 6. When it changes to curd, will its pH value increase or decrease? Why?
Answer: When fresh milk changes to curd, the pH of the solution is likely to decrease. Actually, lactose present in milk gets converted to lactic acid when curd is formed from milk. Therefore, the medium becomes more acidic and its pH decreases.

Question. A sample of bleaching powder was kept in an air tight container. After a month, it lost some of its chlorine content. How will you account for it?
Answer: Bleaching powder if kept even in an air tight container will slowly decompose of its own and form calcium chlorate and calcium chloride. The reaction is called auto oxidation. This will result in decrease in its Chlorine contents. 6CaOCl₂ -----→Ca(ClO₃)₂ + 5CaCl₂

Question. An old man complained of acute pain in stomach. Doctor gave him a small antacid tablet and he got immediate relief. What actually happened?
Answer: The old man was suffering from acute acidity. Antacid tablet contains NaHCO₃. It reacts with the acid HCl formed because of acidity and neutralizes its effect.

Long answer type questions:

Question. Explain why:
(i) Common salt becomes sticky during the rainy season
(ii) Blue vitriol changes to white upon heating.
(iii) If bottle full of Conc. Sulphuric acid is left open in the atmosphere by accident, the acid starts flowing out of the bottle of its own.
Answer: (i) Common salt contains the impurity of MgCl₂ which is of deliquescent in nature. When exposed
to atmosphere, it becomes moist. Therefore common salt becomes sticky during the rainy season.
(ii) Blue vitriol (CuSO₄.5H₂O) upon heating changes to anhydrous copper sulphate which is white in color.
(iii) Concentrated Sulphuric acid is highly hygroscopic. It absorbs moisture from air and gets diluted. Since the volume increases, the acid starts flowing out of the bottle.

Question. (a) What is the action of red litmus on (i) dry ammonia gas (ii) solution of Ammonia gas.
(b) State the observation you would make on adding ammonium hydroxide to aqueous solution of (i) Ferrous Sulphate (ii) Aluminium Chloride.
Answer: (a) (i) Red litmus has no action on dry ammonia because it does not has hydroxyl ion.
(ii) When interact with ammonia solution it turns in blue as the solution has hydroxyl ion.
(b) (i) A green ppt of ferrous hydroxide will be formed
FeSO₄ + 2 NH₄OH -----→Fe(OH)₂ + (NH₄)₂SO₄
(ii) A white ppt is formed
AlCl₃ + 3 NH₄OH ---→ Al(OH)₃ + 3 NH₄Cl

Question. (a) Name the raw materials used in the manufacture of Sodium carbonate in Solvay process?
(b) How is sodium bi carbonate formed during Solvay process separated from a mixture of NH₄Cl and NaHCO₃?
(c)How is sodium carbonate obtained from Sodium bi Carbonate?
Answer: (a) The raw materials used are: NaCl, Lime stone or CaCO₃ and NH₃
(b) NaHCO₃ is sparingly soluble or less soluble in water and gets separated as a precipitate while NH₄Cl remains in solution. The filtrate is removed by filtration.
(c ) NaHCO₃ is converted to sodium carbonate upon heating.
2NaHCO₃ ----→ Na₂CO₃ + H₂O + CO₂

Question. What will you observe when-
(i) Red litmus paper introduced into a solution of sodium carbonate.
(ii) A methyl orange drop is added to dilute hydrochloric acid.
(iii) A drop of phenolphthalein is added to the solution of lime water.
(iv) Blue litmus is introduced into a solution of Ferric chloride.
Answer: (i) The color of litmus paper will change to blue. Sodium carbonate dissolves in to water to form NaOH and Carbonic acid H₂CO₃. The solution is basic in nature since NaOH is a strong base and carbonic acid is a weak acid.
Na₂CO₃ + H₂O -------→ 2 NaOH + H₂CO₃
(ii) In the acidic solution, the color of methyl orange will change to reddish.
(iii) Lime water contains traces of Calcium hydroxide Ca(OH)₂ . It is therefore basic in nature. The colour of phenolphthalein will become pink.
(iv) Ferric chloride solution on reaction with water will form ferric hydroxide and HCl. Since the acid is strong, the solution will be acidic. Therefore the color of blue litmus will change to red. FeCl₃ + H₂O ----------→Fe(OH)₃+ 3HCl

Question. (a) Why does an aqueous solution of an acid conduct electricity?
(b) How does the concentration of hydrogen ion changes the solution of an acid is diluted with water?
(c) Which has a higher pH value ; a concentrated or dilute HCl?
(d) What would you observe on adding dilute HCl to
(i) Sodium bicarbonate placed in a test tube.
(ii) Zinc metal in a test tube.
Answer: (a) An aqueous solution of an acid conducts electricity because in water an acid dissociates to give ions. Since current is carried by the movements of ions, a.q. solution of acid conduct electricity.
(b) Upon dilution, more of acid dissociates into ions Therefore concentration of hydrogen ion increases.
(c ) Although more H+ ions are formed upon dilution , but the number of ions per unit volume decrease. Therefore, pH will increase upon dilution.
(d) (i) CO₂ gas would evolve accompanied by brisk effervescences.
NaHCO₃ +HCl ------→NaCl + CO₂ + H₂O
(ii) Hydrogen gas would evolve accompanied by brisk effervescences.
Zn + 2HCl ---→ ZnCl₂ + H₂

Paragraph/Table and Case Study Based Questions

1. Read the following and answer any four questions from 1(i) to 1(v):

Reshma broke her leg in an accident. She went to see the Dr. Sant Prakash. On examination, Dr. Prakash mixed the white power in water and applied to her leg along with the cotton and gauze. After a while, it turned into white, solid, hard mass. He said that it would support her fractured bone in the right position.

Question. After treatment, the doctor repacked the white powder back into moisture proof, airtight container. Why?
(a) The fungus growth will occur in open
(b) The powder would react to moisture and turn into solid mass
(c) The powder with react to sunlight and turn into solid mass
(d) To prevent the stealing of the powder as it is very expensive
Answer. B

Question. What is 'white, solid hard mass' called as?
(a) Talcum powder
(b) Paris of Plaster
(c) Plaster of Paris
(d) Copper sulphate
Answer. C

Question. The reaction involved in the formation of white mass is :
(a) Combustion
(b) Oxidation
(c) Mineralisation
(d) Crystallisation
Answer. D

Question. Study the following reaction and choose the correct option:
CaSO₄. 1/2 H₂O + 3/2 H₂O → CaSO₄.2H₂O
(a) Reactant is calcium hemihydrate, product is Gypsum
(b) Reactant is Gypsum, product is calcium hemihydrate
(c) Reactant is Gypsum, product is calcium sulphate hemihydrate
(d) Reactant is calcium sulphate hemihydrate, product is Gypsum
Answer. D

3. Sodium chloride is known as common salt. Its main source is sea water. It is also exists in the form of rocks and is called rock salt. Common salt is an important component of our food. It is also used for preparing sodium hydroxide, baking soda, washing soda etc. Sodium Hydroxide is prepared by passing electricity through an aqueous solution of sodium chloride also known as brine. This process is known as chloralkali process. It is white translucent solid. Crystals of sodium hydroxide are deliquescent. It is readily soluble in water and gives strong alkaline solution. Washing Soda is sodium carbonate decahydrate. It is prepared by heating baking soda. Recrystallisation of sodium carbonate gives a compound, which is used for removing permanent hardness of water. It is used in glass, soap and paper industries. It can be used as a cleaning agent for domestic purposes.
Plaster of Paris is is obtained by heating Gypsum upto 373K. On treatment with water it is again converted into gypsum and sets as a hard mass. It is used by doctors for setting fractured bones. It is used for making statues, models and other decorative materials.

Question. What is the chemical formula of plaster of paris?
Answer : CaSO₄.1/2H₂O.

Question. Name the chemical compound obtained by the recrystallization of sodium carbonate.
Answer : Recrystallization of sodium carbonate gives washing soda.

Question. Name the solution that is used to prepare caustic soda.
Answer : Brine solution is used prepare caustic soda.

Question. Which of these statements is incorrect?
(i) On treatment with water plaster of paris is again converted into gypsum.
(ii) Crystals of sodium hydroxide are deliquescent.
(iii) Sodium chloride is known as common salt.
(iv) Plaster of Paris is calcium sulfate hydrates.
Answer : The correct chemical name of plaster of paris is calcium sulfate hemihydrates.
Hence, the incorrect option is (iv).

4.
S. No.   I                       II
1.      Tartaric acid     Calcium hydroxide
2.      Lactic acid       Sodium hydroxide
3.      Formic acid      Ammonia
4.      Citric acid        Magnesium

Question. What does column I represents ?
Answer : Column I represents acids.

Question. What does column II represents ?
Answer : Column II represents bases.

Question. Name one source of citric acid.
Answer : Oranges are good source of citric acid.

Question. What is released by ant’s sting ?
Answer : Formic acid is released by ant’s sting.

5.
S. No.   Test tubes    Nature of Solution
1.         I                 Neutral
2.         II                Acidic
3.         III               Basic
4.         IV               Neutral

Question. State the difference between an acid and base.
Answer : Acids release hydronium ions in the solution and bases give hydroxide ions in aqueous solution.

Question. What is the color of litmus paper for test tube I ?
Answer : The color of litmus paper for test tube I is green.

Question. Give one example of the solution that could be present in test tube II.
Answer : Solution of vinegar in water is a example of solution that could be present in test tube II.

Question. What is the color of litmus paper for test tube III ?
Answer :  The color of litmus paper for test tube III is blue.

6.
S. No.   Name of compound
1.         Plaster of Paris
2.         Baking Soda
3.         Washing soda
4.          Slaked lime

Question. Give one use of plaster of paris.
Answer : Plaster of Paris is used for making statues, models and other decorative materials.

Question. Give chemical formula of baking soda.
Answer : The chemical formula of baking soda is NaHCO₃.

Question. State difference between baking soda and washing soda.
Answer : Sodium hydrogen carbonate (NaHCO₃) is known as baking soda whereas Sodium carbonate (Na₂CO₃) is known as washing soda.

Question. Give chemical formula of slaked lime.
Answer : The chemical formula of slaked lime is Ca(OH)₂.

7.
S. No.     Substances pH value
1.           Lemon juice 2.0
2.           Wine 4.0
3.           Detergent 10.0
4.           Bleach 12.5
Question. What is the nature of bleach ?
Answer :  Bleach is basic in nature.

Question. What is color of litmus for lemon juice ?
Answer : Lemon juice turns blue litmus red.

Question. What is the pH value for neutral solutions ?
Answer : The pH value for neutral solutions is 7.

Question. Name the substances that would turn red litmus blue.
Answer : Detergent and bleach would turn red litmus blue.