ACIDS BASES AND SALT 10

  PRACTICE PAPER 

SUB: CHEMISTRY (2020)

Class X                                                    ACID BASE AND SALT          ___________________________________________________________________________________

I. Multiple Choice Questions

1. 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

2. Base produce
a. hydrogen ions or OH-1
b. hydroxide ions or H+1
c. Hydrogen ions or H+1
d. Hydroxide ion or OH-1

3. Which one of the following can be used as an acid–base indicator by a visually      impaired student?

     a. Litmus

     b.Turmeric

     c. Vanilla essence

     d. Petunia leaves

4. Which among the following is not a base?

a. NaOH

b. KOH

c. NH₄OH

d. C₂H₅ OH

5. Acid produce

a. hydrogen ions or OH-1
b. hydroxide ions or H+1
c. hydrogen ions or H+1
d. hydroxide ion or OH-

6. A sample of soil is mixed with water and allowed to settle. The clear supernatural 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

b. Vinegar

c. Common saltd

d. An antacid 

7. The inner lining of stomach protects vital cells from 
a. base present in food
b. HCl acid secreted by stomach
c. acid present in food
d. helps in killing bacteria and harmful organisms that may be present in food.

i. a and b
ii. b and c
iii.a and d
iv.b and d

8. Which of the following salts does not contain water of crystallisation?

a. Blue vitriol

b. Baking soda

c. Washing soda

d. Gypsum

9. Which of the following are present in a dilute aqueous solution of hydrochloride 

    acid?

    a. H₃O⁺ + ClO⁺

b. H₃O⁺+ OH^-

c. Cl^-+ OH^-

d. unionized HCl

10. To protect tooth decay we are advised to brush our teeth regularly.

    The nature of the tooth paste commonly used is

    a. acidic

    b. neutral

    c. basic

    d. corrosive

11. Bee and plants like nettle secrete 
a. mild acidic substance 
b. highly basic substance 
c. highly acidic substance 
d. mild basic substance
for self defense.

12. Which of the following statements is true for acids?

    a. Bitter and change red litmus to blue

    b. Sour and change red litmus to blue

    c. Sour and change blue litmus to red

    d. Bitter and change blue litmus to red

13. The substance formed by the combination of acid and base is

a. acid
b. base
c. salt
d. none of the above

14. 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

15. The chemical reaction of acid with base is called
a. neutralization reaction.
b. combination reaction
c. decomposition reaction
d. displacement reaction
i. a and b
ii. b and c
iii. a and d
iv. b and d

16. 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

17. An aqueous solution turns red litmus solution blue. Excessa addition of which of the following solution would reverse the change

a. Baking powder

b. Lime

c. Ammonium hydroxide solution

d. Hydrochloric acid

18. Which of the following phenomena occur, when a small amount of

acid is added to water?

a. Ionisation

b. Neutralisation

c. Dilution

d. Salt formation

(i) (a) and (b) 

(ii) (a) and (c)

(iii) (b) and (c) 

(iv) (b) and (d)

19. Non metallic oxides are generally
a. acidic in nature.
b. basic in nature
c. neutral in nature
d. none of the above

20. What happens when a solution of an acid is mixed with a solution of a base in a test tube?

    a. The temperature of the solution increases

    b. The temperature of the solution decreases

    c. The temperature of the solution remains the same

d. Salt formation takes place

(i) (a) only 

(ii) (a) and (c)

(iii) (b) and (c) 

(iv) (a) and (4)

21. Which of the following is acidic in nature?

   a. Lime juice

   b. Human blood

   c. Lime water

   d. Antacid

22. Calcium phosphate is present in tooth enamel. Its nature is
    a. basic
    b. acidic
    c.  neutral
    d. amphoteric

23. Which of the following is not a mineral acid?

   a. Hydrochloric acid

   b. Citric acid

   c. Sulphuric acid

   d. Nitric acid

24. Sodium hydrogencarbonate when added to acetic acid evolves a gas.Which of the following statements are true about the gas evolved?

   a. It turns lime water milky

   b. It extinguishes a burning splinte

   c. It dissolves in a solution of sodium hydroxide

   d. It has a pungent odour

   (i) (a) and (b) 

   (ii) (a), (b) and (c)

   (iii) (b), (c) and (d)

   (iv) (a) and (d)

25. Common salt besides being used in kitchen can also be used as the raw material for making 

   a. washing soda.

   b. bleaching powder

   c. baking soda

   d.  slaked lime

   (i) (a) and (b) 

   (ii) (a), (b) and (d)

   (iii) (a) and (c) 

   (iv) (a), (c) and (d)

26. Which of the following statements is correct about an aqueous solution of an acid and of a base?

  a. Higher the pH, stronger the acid

  b.  Higher the pH, weaker the acid

  c.  Lower the pH, stronger the base 

  d. Lower the pH, weaker the base

  (i) (a) and (b) 

  (ii) (b) and (c)

  (iii) (a) and (d) 

  (iv) (b) and (d)

27. Which  is not true about sodium chloride
a. Sodium chloride is known as brine.
b. Its main source is sea water. 
c. It is also called rock salt.
d. It is basic in nature.

28. 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

29. Which of the following substance will not give carbon dioxide on treatment with dilute acid?
   a. Marble
   b. Limestone
   c. Baking soda
   d. Lime

30. 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 solution of sodium hydroxide on the hand
   d. Neutralise the acid with a strong alkali

31. 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

II. Fill in the blanks

a. Organic acids are derived from living organisms like …….. and ……..
b. Mineral acids are……... acids. They are dangerous.
c. Strong acids are completely dissociate into its ……. in aqueous solutions.
d. ………...acids have a low concentration of acids in aqueous solution

and ………. acids have a high concentration of acids in aqueous solutions.
e. A scale for measuring hydrogen ion concentration in a solution, called ………. .
f. Water soluble bases are called……..
g.The pH of mouth should always be more than …………
h. …………. are substances which indicate the acidic or basic nature of

the solution by their ………....
i. The pH value for acids is ………

III. True / False

a. Acid have a slippery, ‘soapy’ feel.
b. Base dissolve fatty material.
c. Base turn red litmus blue.
d. Stomach secretes H2SO4 to kill bacteria in the food. 
e. Higher  pH of some food can cause tooth decay.
f. The pH of salts solution depends on the strength of acids and base combined in neutralization reaction.

g. The water must be added slowly to acid with constant stirring.
h. The process of dissolving an acid, or a base in water is a endothermic reaction.

IV. Assertion and Reasoning questions

In the following questions a statement of Assertion is followed by a statement of Reason. Mark the correct choice as

a. If both Assertion and Reason are true and Reason is the correct explanation of Assertion.

b. If both Assertion and Reason are true but Reason is not the correct -explanation of Assertion.

c. If Assertion is true but Reason is false.

d. If Reason is true but Assertion is false.

e. If both Assertion and Reason are false.

Assertion: Acetic acid does not act as an acid in benzene solution.

Reason: Benzene is non-polar

Assertion Calcium oxide is a base but not an alkali.

Reason: Calcium oxide is insoluble in water.

Assertion There is no change in the colour of litmus paper when brought in contact with distilled water.

Reason: Litmus Paper is used to find whether an solution is Acidic or Basic.

Assertion: When bleaching power is left in the open, its colour changes from blue to white.

Reason: The change in colour as oxygen breaks away from the compound.

Assertion Sodium and Potassium is kept inside kerosene.

Reason: Sodium does not react with organic solvents like kerosene.

IV. Match the followings:

ORGANIC ACID	SOURCES
a. Citric acid b. Acetic acid c. Tartaric acid d. Oxalic acid e. Lactic acid	i. Tomato and guava ii. Tamarind iii. Curd and sour milk. iv. Vinegar v. Fruits

 V. Match the following

INORGANIC ACIDS	CHEMICAL FORMULA
Sulphuric acid Hydrochloric acid Nitric acid Carbonic acid	i. HNO3 ii. H2CO3 iii. H2SO4 iv. HCl

VI. Match the following

Sulphuric acid Acetic acid Hydrochloric acid Nitric acid Carbonic acid Citric acid

i. Weak acid ii. Strong acid

VII. Match the following

SALT	USES
a. Epsom salt           (MgSO4)  b. ammonium nitrate(NH4NO3)  c. baking soda (NaHCO3)	i. used as fertilizer, ii. used in cooking. iii. used in bath salts,

 

VIII. Match the following

Indicator	Colour in acidic medium	Colour in basic medium
1. Blue litmus  2. Red litmus 3. Methyl orange 4.Phenolphthalein	a.Red b.blue c. Colour less d.pink e.yellow	i..Red ii.blue iii. Colour less iv.pink v.yellow

IX. Match the following

Name of Salt	Formula
a. Bleaching powder b. Baking Soda c. Washing Soda d. Plaster of Paris e. Gypsum	i. CaSO4. ½ H2O ii. Na2CO3.10H2 iii. NaHCO3 iv. CaSO4. 2H2O v. CaOCl2,

X. Sanswer type questions:

1. Name the acid present in lemon juice.
2. Name the acid present in ant sting.
3. Name the acid presents in our stomach.
4. What is common to both acid and base?
5. Write the name of a compound known as Lewis acid & one as Lewis base.
6. How zinc metal reacts with conc. caustic soda? Write the chemical equation.
7. What is the alternate name of the term negative log [H⁺]?
8. Name the plant which on rubbing gives relief to the skin affected by stinging nettles(methanoic acid).
9. If H⁺ the concentration of a solution is 1 x 10^-2 Mol/L, what will be its pH value?
10. Give one example of each of the basic oxide and acidic oxide.
11.  Give an example of a natural indicator and synthetic indicator.
12. Write the name of a highly water-soluble base and strong acid with the molecular formula.
13. Name the gases evolved at anode and cathode by the electrolysis of brine?
14. Amongst dry HCl and HCl solution, which can show the acidic property? 
15. A chemical substance is used to set the fractured bones in the right position. Give the chemical name and formula of this substance.
16. What is the salt of sulphuric acid, nitric acid, and hydrochloric acid?
17. Write three strong acids and three weak acids.
18. What is the ideal pH of the soil for the healthy growth of a plant? 
19. What is the difference between baking powder and washing soda?
20. Which gas is usually liberated when an acid reacts with a metal?
21. Which is a stronger acid with pH = 5 or with pH = 2 ?
22. What is the effect of dilution on H⁺ ion concentration of an acid?
23. What are strong acid or base and weak acid or base?
24. A compound that is prepared from gypsum has the property of hardening when mixed with the proper quantity of water. Identify the compound and write its chemical formula.
25. A compound that is formed due to the recrystallization of sodium carbonate. Identify the compound and write its chemical formula
26. What do you understand by the term water of crystallization? 
27. Name a salt which does not contain water of crystallization.
28. Give reasons why chips manufacturers usually flush bags of chips with a gas such as nitrogen.
29. Fresh milk has a pH of 6. When it changes into curd will its pH value increase or decrease? Why?
30. What would be the colour of litmus in a solution of sodium carbonate?
31. Why does tooth decay start when the pH value of the mouth is lower than 5.5?
32. How does the use of toothpaste help in preventing tooth decay caused due to eating chocolate and sweets?
33. What effect does an increase in the concentration of H⁺ in a solution have on the pH of the solution?
34. Which one of these has a higher concentration of H⁺ ions? 1M HCl or 1M CH₃COOH.
35. During the summer season, a milkman usually adds a very small amount of baking soda to fresh milk. Give one reason.
36. Give chemical equations to show the changes that occur when clean coloured ferrous sulphate crystals are heated. Mention the change observed as well as the reason for this change.
37. The plaster of Paris should be stored in a moisture-proof container. Why?  
38. How does the change in pH value of milk when it changes to curd. Explain.
39. Explain and write the chemical formula of baking soda. How is baking soda prepared?
40. Write the reactions which take place when baking soda is heated during cooking.
41. What is a neutralization reaction? Give two examples.
42. A knife which is used to cut fruit, was immediately dipped into water containing drugs or blue Litmus solution if the colour of the solution is changed to read what inference can be drawn about the nature of the fruit? And why?
43. The colour of copper sulphate solution changes when an iron nail is dipped in it. State the reason for giving the chemical equation for the reaction involved.
44. Write an equation to show the reaction between the plaster of Paris and water.
45. Name a substance that on treatment with chlorine yields bleaching powder.
46. Name the sodium compound which is used for softening hard water.

XI. Short answer type questions: 

1. Write the name of acids in the following:
   (i) Tomato.
   (ii) Vinegar.
   (iii) Lemon.
   (iv) Apple.
2. A piece of zinc metal is dropped in a dilute solution of hydrochloric acid.
   (a) Which gas is liberated when a metal reacts with an acid?
   (b) How will you test the presence of this gas?
   (c) Is it lighter or heavier than air?
   (d) How will you collect the above gas? 
3. A white powder is added while baking bread and cakes to make them soft and fluffy. What is the name of the Powder? What are the main ingredients in it? What are the functions of each ingredient?
4. Classify the following as acidic, basic, or neutral salts: NaCl, KNO₃, AlCl₃, ZnSO₄, CuSO₄, CH₃COONa, NaHCO₃, Na₂CO₃.    
5. Salt A commonly used in bakery products on heating gets converted into another salt B which itself is used for removal of hardness of water and a gas C is evolved. The gas C when passed through lime water, turns it milky. Identify A, B, and C.
6. The solution of hydrochloric acid is added to the solution of sodium hydroxide solution containing phenolphthalein indicator dropwise. After some time the pink colour of the solution disappears.
   (a) Identify the type of reaction
   (b) Why the pink colour of the solution fades away after some time? 
7. Name the acid and base used to form the following salts:
   NaHCO₃, ZnSO₄, AlCl₃.  
8. A milkman adds a small amount of baking soda to fresh milk.
   (a)Why does the milkman shift the pH of fresh milk is slightly alkaline?
   (b)Why does the milk take a longer time to set as curd?
9.  A green coloured hydrated metallic salt on heating, loss its water of crystallization and give the smell of burning sulphur. Identify the salt and write down the reaction involved.
10. While diluting an acid why is it recommended that the acid should be added to water and not water to the acid? 
11. Dry HCl gas does not change the colour of dry blue litmus paper. Give reasons.
12. HCl and HNO₃ show acidic characteristics in aqueous solution, while alcohol and glucose solutions do not. Give reasonHCl and HNO₃ show acidic characteristics in aqueous solution, while alcohol and glucose solutions do not. Give reason. 
13. Name the gas evolved when sodium hydrogen carbonate is made to react with dilute hydrochloric acid. How will you test the gas?
14. A substance X, which is an oxide of metal is used intensively in the cement industry. This element is present in bones also. On treatment with water, it forms a solution that turns red litmus blue. Identify X and also write the equation for its chemical reactions with water.
15. How will you prove that a given salt is a carbonate of metal?
16. You might have seen lemon or tamarind juice being used to clean the tarnished surface of copper vessels. Explain why these sour substances are effective in cleaning the vessels? 
17. Though the compounds such as glucose and alcohol have hydrogen atom in their molecules yet they are not categorized as acids. Why?
18. What is a neutralization reaction? Give an example.
19. State the chemical name of the Plaster of Paris. Write a chemical equation to show the reaction between the Plaster of Paris and water. 
20. What is the colour of FeSO₄ crystals? How does this colour change upon heating? Give a balanced chemical equation for the changes. 
21. Classify the following salts into acidic, basic and neutral: Potassium Sulphate, ammonium chloride, sodium carbonate, sodium chloride.
22. Write chemical equations that show Aluminium oxide reacts with acid as well as base,
23. Crystal of a substance changed their colour on heating in a closed vessel but regained after some time, when they were allowed to cool down.
    (a) Name one such substance (b) Explain the phenomenon involved.
24. (a) How is the concentration of hydronium ions (H₃O⁺) affected when a solution of an acid is diluted?
    (b) How is the concentration of hydroxide ions (OH^-) affected when excess base is dissolved in water?
25. What is meant by the term pH of the solution? The pH of rainwater collected from two cities A and B was found to be 6 and 5 respectively. The water in which the city is more acidic?
26. Explain and write the chemical formula of baking soda. How is baking soda prepared?
27.  What is a neutralization reaction? Give two examples.
28. A knife which is used to cut fruit, was immediately dipped into water containing drugs or blue Litmus solution if the colour of the solution is changed to red what inference can be drawn about the nature of the fruit? And why?
29. The colour of copper sulphate solution changes when an iron nail is dipped in it. State the reason-giving the chemical equation for the reaction involved.
30. The colour of copper sulphate solution changes when an iron nail is dipped in it. State the reason-giving the chemical equation for the reaction involved.
31. What are strong acid or base and weak acid or base?
32. A compound that is prepared from gypsum has the property of hardening when mixed with the proper quantity of water. Identify the compound and write its chemical formula.
33. Give chemical equations to show the changes that occur when clean coloured ferrous sulphate crystals are heated. Mention the change observed as well as the reason for this change.
34. The plaster of Paris should be stored in a moisture-proof container. Why?  
35. Write the chemical formula of bleaching powder. Write a balanced chemical equation involved in the preparation of bleaching powder. 

XII. Long answer type questions: 

1. White hydrated salt of sodium is used for removing permanent hardness from water.
   (a) Write the chemical name and formula of the salt.
   (b) Write the steps of preparation of the salt.
   (c) Mention one domestic use and one industrial use of the compound.  
2. In one of the industrial processes for the manufacture of sodium hydroxide, a gas X is formed as a by-product. The gas X reacts with lime water to give a compound Y which is used as a bleaching agent in the chemical industry. Identify X and Y giving the chemical equation of the reaction involved.
3. Comment on the following :
   (i) An acid reacts with substance X produces a gas that burns with a pop sound. What is the nature of X?
   (ii) An acid when reacting with Z, produces CO₂ gas. What can be Z?
   (iii) CaO and SO₂ are two oxides. Name the oxide which will base?
   (iv) A sodium compound is used for removing the permanent hardness of the water. Name the compound.
   (v) A substance on treatment with chlorine gas yields bleaching powder. Name the substance.
4. What will be the action of the following substances on litmus paper? 
   (i) Dry HCl gas. 
   (ii) Moistened NH₃ 
   (iii) Lemon juice. 
   (iv) Carbonate soft drink 
   (v)Curd 
   (vi) Soap solution.
5.  I. Name the acid present in ant stings and gives its chemical formula. Also, give the common method to get relief from the discomfort caused by the ant sting. Write the colour of the following indicators in acid, base and neutral solution: 
   (i) Litmus 
   (ii) Phenolphthalein 
   (iii) Methyl orange (iv)Turmeric juice. 
   II. When 1 drop of orange juice is added to pure water how the pH value will vary for water? If one drop of lemon juice is also added, will there be any more change in the pH value?
6. 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, it gives a compound Z, used for disinfecting drinking water. Identify X, Y, G, and Z.
7. For the baking cake, baking powder is taken. If at home you have backing soda instead of baking powder:
   (i) How will it affect the test of the cake?
   (ii) How can baking soda be converted into baking powder?
   (iii) What is the role of tartaric acid added to baking soda?
8. What is bleaching powder? How is it prepared? list two uses of bleaching powder.
   Or 
   [Do your self:  (a) Write the common name of CaOCl₂ How is it prepared. Write the chemical equation of the reaction involved in the process. Give any two uses of it.
   (b) Write the chemical name of washing soda. How is it prepared? Give the relevant chemical equation.]
9.  (a) What would be the colour of the solution when copper oxide and dilute hydrochloric acid are mixed?
   (b) Write a chemical equation that represents that the effect of a base is nullified by an acid and vice versa
10. A dry pellet of a common base B, when kept in open absorbs moisture and turns sticky. The compound is also a by-product of Chlor- alkali process Identify B. What type of reactions occurs when B is treated with an acidic oxide.
11. Write the chemical formula of the following salt and obtained from which acid or base:
    (i) Ammonium chloride.    ( ii) Copper Sulphate
    (iii) Sodium chloride          (iv) Magnesium Nitrate
    (v) Potassium Sulphate.    (vi) Calcium nitrate.
12. While constructing a house a builder select marble flooring and marble tabletop for the kitchen where vinegar, juices of lemon, and tamarind, etc. are more often used for cooking. Will you agree to this selection and why?
13. A white powder A is the mild non-corrosive base and is used in the preparation of cakes. When the powder A is heated it gives another powder B.The powder B is recrystallized to get a substance C that has detergent properties. Identify A, B, and C and also write balanced chemical equations for the conversions of A to B and then B to C.
14.  A substance is used as an antacid reacts with hydrochloric acid to produce a gas Y which is used in extinguishing the fire.
    (a) Name the substance X and gas Y.
    (b) Write a balanced chemical equation of the reaction between X and hydrochloric acid.
15.   A substance is used as an antacid reacts with hydrochloric acid to produce a gas Y which is used in extinguishing the fire.(a) Name the substance X and gas Y.
    (b) Write a balanced chemical equation of the reaction between X and hydrochloric acid.
16. (a) Write the name given to bases that are highly soluble in water. Give an example.
    (b) How is tooth decay related to pH? How can it be prevented?
    (c) Why does bee-sting cause pain and irritation? Rubbing of baking soda on the sting area gives relief. How?
17.  I. Differentiate between strong and weak acids. Identify the strong and weak acids from the following list of acids: hydrochloric acid, acetic acid, formic acid, nitric acid.
    II. What is meant by the term hydrated salt? Give two examples of hydrated salt which are white and state their chemical formula.
18. A compound that is prepared from gypsum has the property of hardening when mixed with the right quantity of water.
    (a) Identify the compound and write its chemical formula.
    (b) Write the chemical equation for its preparation.
    (c) List any two uses of the above compound.
19.  A student dropped a few pieces of marble in dilute hydrochloric acid contained in a test tube the evolved gas was then passed through lime water, what change would be observed in lime water? What will happen if excess of gas is passed through lime water?
20. . I. You are given two solutions A and B. The pH of solution A is 6 and pH of solution B is 8 
    (a) Identify the acidic and basic solutions.
    (b) Which solution has more H⁺  ion concentration? Give reasons for your answer.
    II Why is HCl a stronger acid than acetic acid? Explain.
21.  When a concentrated aqueous solution of substance X is electrolyzed, then NaOH, Cl₂ and H₂ are produced.
    (a) Name the substance X
    (b) What is the special name of this process and why is it so-called?
    (c) Which gas is liberated at the anode? List one uses of this process.
22. What is the chloralkali process? Why is it so-called? Write the equation for the reaction.
    Name the three products of the chloralkali process. Write one commercially or industrially important material is that can be prepared from each of these products.
23.  "Sodium hydrogen carbonate is a basic salt "Justify the statement. How is it converted into washing soda? Explain.
24. There are three test tubes A, B, C. Test tube A has an acidic solution, test tube B has a basic solution and test tube C has distilled water. Identify the contents of each test tube with the help of litmus paper.
25. A liquid has a pH of less than 7 which is represented as an acidic solution.
    (a) State the nature of the solution if its pH increases from 7 to 14.
    (b) Mention the ion concentration increases with an increase in pH value. 
    (c) Suggest a method that is generally used for measuring PH value.
26.  A few crystals of copper Sulphate is heated in a dry boiling tube:
    (a) What is the colour before and after heating?
    (b) What is the reason for the colour change?
    (c) Can its original colour be restored? How?
27. I.Giving reasons for each state which of the following will conduct electricity and which will not :
    (a) A solution of glucose
    (b) Dilute hydrochloric acid?  
    II.(a) If acetic acid and hydrochloric acid of the same concentration are taken, which of the two is stronger acid and why?
    (b) How is the strength of an acid affected when some water is added to it?
28. I. While eating food, you happen to spill some curry on your white shirt. You immediately scrub with soap. What happens to its yellow colour?  What happens to this stain when the shirt is washed with plenty of water? 
    II. (a) Write the chemical formula of plaster of Paris and Gypsum.
    (b) How can plaster of Paris be converted into gypsum?
    (c) List anyone uses of plaster of Paris.
29. Rahul has been stung by the honey bee and is in great pain.            (a) What could be the reason for this burning pain? State the type of chemical compound that can be applied to the affected area to give relief to Rahul.
    (b) Write the name and formula of each of the following:
    (i) an acidic salt (ii) a basic salt (iii) a neutral salt.
30.  I. A local musician was showing magic in a village street. He took eggshells and poured a solution over it. As a result, if an effervescence were formed. When he took a burning matchstick over it, went off: 
    (a) Identify the solution poured and a substance present in eggs. 
    (b) What is the reason behind the effervescence? 
    (c) Write its balanced chemical equation. 
    (d) Give the common name of the substance present in eggshell. 
31.  (a) Acids as well as bases ionized in water. Name the ions produced by each in water. 
    (b) If we have hydrochloric acid and acetic acid of equal concentration, which will be a strong acid and why? 
    (c) How will the concentration of hydrogen ion get effected if acid is diluted? 
32. (a) Identify the acid and base whose combination forms the common salt that you use in your food. Write the formula and chemical name of this salt. Name the source from where it is obtained.
    (b)What is rock salt? Mention its colour and the reason due to which it has this colour.
    (c) What happens when electricity is passed through brine? Write the chemical formula for it.
33.  (a) Write the chemical name and chemical formula of washing soda.
    (b) How it is obtained from sodium chloride? Give equations of the reaction?
    (c) Why is it called a basic salt? Give it's anyone uses?
34.  (a) Name the gas which is liberated when an acid reacts with metal.  How will you test the presence of this gas?
    (b) Write the chemical equation for the reaction of Zinc metal with.
    (i) Hydrochloric acid and  (ii) With Sodium hydroxide. Write the chemical name of salt obtained in each case. 
    (b)Identify the acid and base for Ammonium chloride salt. What would be the nature of the salt? Mention the pH range of the salt.
35.  Write a chemical name of Na₂CO₃.10H₂O and Na₂CO₃. Write the significance of 10H₂O. Mention the term used for water molecules attached with a salt. With the help of the chemical equation, explain the method of preparation of both Na₂CO₃.10H₂O and Na₂CO₃. Also, list two uses of Na₂CO₃.10H₂O.
36.  (a) Mention the pH ranges within which our body works. Explain how antacid give relief from acidity? Write the name of one such antacid.
    (b) Mention the nature of toothpaste.
37.  (a) A metal compound X reacts with dilute H2SO₄ to produce effervescence. The gas evolved extinguishes a burning candle. If one of the compounds formed is calcium Sulphate, then what are X and the gas evolved? Also, write a balanced chemical equation for the reaction reach which occurred.
    (b) Name one antacid. How does it help to relieve indigestion in the stomach 
    (c) A farmer treats the soil with quick lime or calcium carbonate. What is the nature of soil? Why does the farmer treat the soil with quicklime?
38.  I. Write a balanced chemical equation only for the following chemical properties of acids: 
    (a) When an acid reacts with metal.
    (b) When an acid reacts with metal bicarbonate
    (c) When an acid reacts with a base.
    II. Three solution A, B, C has pH values 5, 8 and 10 respectively. Among the three which solution has maximum hydrogen ion concentration? Classify the nature of the three solutions as acidic or basic.
39.  (a) Study the following chemical equation. CaSO₄.2H₂O→CaSO4.1/2H₂O +3/2H₂O.
    Name the reactant and the product and mention one use of the product.
    (b) The following salts are formed by the reaction of an acid with a base. Name the acids and base from which these salts are formed. Also mention the nature of the salt, whether it is acidic or basic.
    (i) Sodium chloride 
    (ii) Ammonium nitrate.
40.  Under what soil condition do you think a farmer would treat the soil of these fields with quick lime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate)?
41.  Five solutions A, B, C, D, and E, when tested with universal indicator, showed pH as 4, 1, 11, 7 and 9 respectively. Which solution is it?
    (i)  Neutral, 
    (ii) Strongly alkaline, 
    (iii) Strongly acidic, 
    (iv) Weakly acidic, 
    (v) Weakly alkaline. 
    Arrange the pH in increasing order of hydrogen-ion concentration.
    Or  
    (a) Explain why is hydrochloric acid a strong acid and acetic weak acid? How can it be verified?
    (b) Explain why the aqueous solution of acid conduct electricity.
    (c) You have 4 solutions A, B, C, D. The pH of solutions of A is 6, B is 9, C is 12 and D is 7, 
    (i) Identify the most acidic and most basic solution.
    (ii) Arrange the above four solutions in the increasing order of H⁺ ion concentration.
    (iii) State the change in colour of pH paper on dipping in solutions and D.