SCERT KERALA TEXTBOOKS SOLUTIONS & NOTES: STD IX Chemistry (English Medium) Chapter 05 ACIDS, BASES, SALTS

 SCERT KERALA TEXTBOOKS SOLUTIONS & STUDY NOTES: Class 9 Chemistry (English Medium) Chapter 05 ACIDS, BASES, SALTS 

Textbooks Solution for Class 9th Chemistry (English Medium) | Text Books Solution Chemistry (English Medium) Chapter 05 ACIDS, BASES, SALTS 

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ഈ അദ്ധ്യായം Malayalam Medium ഇവിടെ ക്ലിക്ക് ചെയ്യുക  

Chemistry Questions and Answers in English

Class 9 Chemistry Questions and Answers

Chapter 05 ACIDS, BASES, SALTS 

ഈ അദ്ധ്യായത്തിന്റെ Work Sheet - നായി ഇവിടെ ക്ലിക്കുക 

* Soda water is made by dissolving carbon dioxide in water under high pressure.

1. Choose the molecular formula of soda water from the following.

[ H₂SO₄, H₂CO₃, H₂SO₃, HNO₃ ]

2.What change in colour do you observe when a blue litmus paper is dipped in soda water.

3. Give a reason for the colour change

Ans.

1. H₂CO₃

2. Turns red 

3. Soda water contains carbonic acid. Acid turns blue litmus red

 

* a) Find the odd one out

[ Na₂O, MgO, SO₂, Al₂O₃ ]

b) Write down the molecular formulae of the acid formed when the oxide gets dissolved in water.                

c) Write down the ionisation reaction of the acid obtained in          

Ans.

1) SO₂

2) H₂SO₃                            

3) H₂SO₃ ------>H++ HSO₃ -                                     

4. HSO₃- -------> H+ + SO3² -                                            

* What are the methods used to identify acids and alkalies

Ans: Using indicators like litmus, phenolphthalein and methyl orange.

* Equations given below represent the ionisations of two acids. Complete the equations.

H₂CO₃  --------->    .....P....... + CO₃²-

HNO₃ --------> H+ + ......Q.......

a) What are P and Q

b) Which one of them is a monobasic acid? 

Ans.

1. P - 2H+ / H+

Q  -  NO₃-

2. HNO₃

* Find the characteristics of the substances given in the table below using litmus papers.

Substance	Change in the colour of litmus	Characteristics
Vinegar
Lime water
Soap solution
Hydrochloric acid

Ans.

Substance	Change in the colour of litmus	Characteristics
Vinegar	Blue turns red	.Acidic
Lime water	Red litmus turns blue	Alkaline
Soap solution	Red litmus. turns blue	Alkaline
Hydrochloric acid	Blue litmus turns red	Acidic

* Molecular formulae of a few acids are given.

[H2SO₃, H₂CO₃, HNO₃, H₂SO₄]

a) Find the odd one out.

b) Write down the ionisation equation of this acid.

Ans.

a) HNO₃       

b) HNO₃ -------> H+ + NO₃-                                                   

* Some water is taken in a beaker.

1. What is the pH value of water?                  

2. Some caustic soda is added to water taken in the beaker. Is there any change in the pH value of the resulting solution? Justify your answer.

Ans.

1. 7

2. pH value increases.

Caustic soda is an alkali. So the resulting solution gets alkaline in nature  

* Complete the table given below 

Molecular formulae	Cation	Anion
Ca3(PO4)2	Ca2+	.....(a).....
NaCl	.....(b).....	Cl-
MgSO4	Mg2+	.....(c).....
NH4Cl	.....(d).....	Cl-

Ans.

1. (PO₄)³-

2. Na+

3. (SO₄)²-

4. NH₄+ 

* Take a small piece of zinc in a test tube as shown in the figure. Add 2ml of dilute hydrochloric acid using a dropper. Show a burning match stick at the mouth of the test tube. Record the observation.

Ans: Burn with a ‘pop’ sound

What would be the reason?

Ans: Hydrogen gas liberated burns

Now complete the chemical equation of this reaction

Zn + 2HCl → ZnCl₂ + …………..

Answer:

Zn + 2HCl → ZnCl₂ + H₂

Acids react with reactive metals to form hydrogen gas

* A few acids and alkalies are given in the box)

NaOH, Mg(OH)2, HCl, H2SO4, H3PO4

1. Which of them is a tribasic acid?

2. Which acid is used to produce the salt MgSO₄?

3. Complete the following chemical equation.

.....A........ + HCl           NaCl + .......B......

Ans.

1. H₃PO₄                          

2. H₂SO₄                           

3. A - Na OH                          

B - H₂O  

  

* Now complete the chemical equation of this reaction

Zn + ₂HCl → ZnCl₂ + …………..

Ans:

Zn + 2HCl → ZnCl₂ + H₂

* Equations given below represent the ionisations of two acids. Complete the equations.

H₂CO₃. ---------> .....P....... + CO₃^2-

HNO₃  ---------->  H⁺ + ......Q.......

a) What are P and Q

b) Which one of them is a monobasic acid?

Ans.

1.   P - 2H⁺ / H⁺

Q  -  NO₃^- 

2.   HNO₃

* Take some calcium carbonate (marble pieces) in a boiling tube as shown in the figure. Add dilute hydro¬chloric acid to it through a thistle funnel. Pass the evolving gas through clear lime water taken in a test tube. Which is the gas that comes out through the delivery tube?

Ans: Carbon dioxide

.

* What is your observation when this gas is passed through clear lime water?

Ans: LimeWater turns milky

When acids react with carbonates, carbon dioxide (CO2) gas is liberated.

* Given below are equations of the reactions taking place when hydrochloric acid dissolves in water.

HCl ---------> H⁺ + Cl -

H⁺ + H2O ----------->    ......A.......

1. What is A in this equation?   

2. The following equations show the ionisation of H2SO₄. Complete the equation.

H2SO₄ -------->  H⁺+ ......B.......                        

B ------------->  H⁺+ ......C......    

Ans.

1. H3O + / Hydronium ion  

2. B - HSO₄- (Bisulphate ion‍ )   

C - SO₄² (Sulphate ion)     

* From the characteristics given below, find out those suitable for acids and put (✓) Mark.

1. Have an alkaline taste.

2. Turn blue litmus red

3. React with carbonates to form carbon dioxide gas

4. Soapy to touch

5. Liberate hydrogen on reaction with highly reactive metals like Mg and Zn

6. Have a sour taste

7. Turns red litmus blue

Ans:

1. Have an alkaline taste.

2. Turn blue litmus red (✓)

3. React with carbonates to form carbon dioxide gas (✓)

4. Soapy to touch

5. Liberate hydrogen on reaction with highly reactive metals like Mg and Zn (✓)

6. Have a sour taste (✓)

7. Turns red litmus blue

* Classify the following into acidic oxides and basic oxides.

MgO, NO2, K2O, SO2

Ans.
Acidic oxide: NO₂, SO₂
Basic oxide:  K₂O, MgO 

* Which component is responsible for the common properties of acids
Ans: H

* Chemical equations showing the formation of oppositely charged ions when hydrochloric acid (HCI) and nitric acid (HN03) dissolve in water are given.
HCI → H⁺+Cl^–
HNO₃ → H⁺+ NO^–
a) Which are the ions present in HCl solution?
b) Which are the ions present in HNO3 solution
c) Which is the ion common to both?
Ans:
a) H⁺ and Cl^–
b) H⁺ and NO₃^–
c) H⁺

* What are acids?
Ans:
Acids are substances which can increase the concentration of hydrogen (H⁺) ions in an aqueous solution.

* List the acids that are present in lime juice, curd, tamarind, vinegar.
Ans:
Lime juice — Citric acid
Curd — Lactic acid
Tamarind — Tartaric acid
Vinegar — Acetic acid

* Write the chemical equation for the ionization of HCl.
Ans: HCl → H⁺+Cl^–

* How many hydrogen ions are released when one molecule of HCI is ionized?
Ans: one H⁺

* What is the basicity of an acid?
Ans:
The number of hydrogen ions that can be donated by one molecule of acid is its basicity.
If the basicity is 1, it is called monobasic acid.

* Write the ionization equation of nitric acid (HNO3) and find its basicity.
Ans:
HNO₃ → H⁺ +NO^–₃
Basicity -1

* Write the chemical equation for the ionization of the sulphuric acid (H2S04)
Ans:
H2SO₄ → H⁺ + HSO^–₄ (bisulphate ion)
HSO^–₄ → H+ + SO^2–₄ (sulphate ion)

* How many hydrogen ions are released when one molecule of H₂SO₄ gets ionized? What is its basicity? ’
Ans:
Two H+ ions basicity = 2
It the basicity of acid is 2,
it is said to be a dibasic acid.

* Complete the ionization equation of phosphoric acid (H3PO4).
H₃PO₄ → ………… + PO^3–₄(Phosphate ion)
Ans:
H₃PO₄ → 3H+ + PO^3–₄ (Phosphate ion)

* What is the basicity of H₃PO₄?
Ans:
3
If the basicity is 3,
the acid is called a tribasic acid.

* The chemical formulae of some acids are given in the box. Pick out monobasic and dibasic acids.
H₂CO₃, HNO₃, H₃PO₄, H₂SO₃, HCI, H₂SO₄
Ans:
Monobasic: HNO₃, HCI
Dibasic: H₂CO₃, H₂SO₃, H₂SO₄

* How do you make soda water? Write the equation of this reaction.
Ans:
CO₂ is dissolved in water to make soda water.
H₂O + CO₂ → H₂CO₃ (Carbonic acid)

* Complete the equation of the dissolution of SO₂ in water.
………… + ………….. → H₂SO₃ (sulfurous acid)
Ans:
SO₂ + H₂O → H₂SO₃ (sulfurous acid)
CO₂, SO₂ and NO₂ are non-metallic oxides. Generally, compounds formed by the reaction of non-metallic oxides with water are acidic.

* Given below is the equation of reaction between calcium oxide and water
Cao + H₂O --------> ........A.........
1. Identify product A.
2. What is the nature of A? Suggest a method to identify A.
Ans.
1. Ca(OH)₂ / Calcium hydroxide
2. Alkaline nature
3. Red litmus turns blue.

* Choose the statements suitable for acids

1. Have an alkaline taste.

2. Turns red litmus blue

3. Turns blue litmus red

4. Have a sour taste

Ans.

Turns blue litmus red              

Have sour taste  

* The name of some familiar acids and their chemical formulae are given in the table below. Complete the table.

Ans:

Name of acid	Chemical formula
Hydrochloric acid	HCI
Nitric acid	HNO3
Carbonic acid	H2CO3
Sulphuric acid	H2SO4

 

* What is acid rain?
Ans:
In industrial areas and townships, the chances of air pollution are very high. In such regions, gases like SO₂ and NO₂ reach the atmosphere in larger amounts. These gases dissolve in rainwater and reach the soil as acids. This is known as ‘acid rain’.

* What are the environmental problems caused by acid rain?
Ans:

• Plants lose their ability to produce carbohydrates through photosynthesis as their leaves are de- strayed.

• Severe acid rain destroys the greenery of a region.

• The acidic nature of water causes the death and destruction of fish and corals.

* What measures are to be taken against the environmental issues caused by acid rain?
Ans:

• Reduce the excessive use of fossil fuels.

• Before using fossil fuels, remove sulfur compounds from them as far as possible.

* Burn a neatly rubbed and cleaned magnesium ribbon. Record the observation. What would be the white powder obtained?
Ans: Magnesium burns brightly and a white powder is formed. The white powder formed is magnesium oxide (MgO)

* Take the product in a watch glass and add two or three drops of water. Find its nature using litmus paper.
Ans: Red litmus turns to blue. MgO is alkaline in nature.

* Write the chemical equation of this reaction.
MgO + H₂O → Mg(OH)₂
Ans. magnesium hydroxide

* Take some water in a beaker, add some quick lime (calcium oxide) and stir it. Take some clear solution in a test tube from the beaker and add a drop of red litmus solution.
a) What do you observe?
b) What is the substance formed when calcium oxide reacts with water? Complete the chemical equation of the reaction.
Cao + H₂O → ……………
c) What do you infer about the nature of this substance from this litmus test?
Ans.
a) The solution turns to blue
b) CaO + H₂O → Ca(OH)₂
c) Ca(OH)₂ is alkaline in nature
c) Ca(OH)₂ is alkaline in nature

* Are MgO and CaO metallic oxides or non-metallic oxides?
Ans:
Metallic oxides
Metallic oxides generally exhibit characteristics of bases. The bases that dissolve in water are called alkalies.

* From the oxides given below, find out the basic oxides. K₂O, SO₂, P₂O₅, MgO, CaO, NO₂
Ans:
Basic oxides- K₂O, MgO, CaO

* pH values of a few substances are given in the table given below. Answer the following questions

Substances	pH value
A	7
B	14
C	2

1. Which one of them shows a neutral nature?
2. Which substance among them usually react with metals to produce hydrogen gas?
3. Name the product formed when B and C combine
4. Identify the gas formed when the substance C reacts with carbonates?
Ans.
1. A                          
2. C                                 
3. H₂O                                  
4. CO₂                                         

* pH Value of substances P, Q and R are given in the table. Answer the following questions.

Substance	pH value
P	2
Q	13
R	7

1. Which the substance is acidic in nature?
2. Which one of them turns red litmus blue?
3. What happens to the concentration of H+ ions on increasing pH value?
4. What is the nature of substance R?
Ans.
1. P
2. Q
3. Decrease
4. Neutral solution

* Write the equation of the dissolution of sodium hydroxide in water.
Ans:
NaOH → Na⁺ +OH^– (hydroxide ion)

* Complete the given equation of the ionization of calcium hydroxide.
Ca(OH)₂ → Ca⁺₂ +……….
Answer:
Ca(OH)₂→ Ca⁺₂ + 2OH^–

* Which is the common ion released when alkalies dissolve in water?
Ans:
OH-
Alkalies are substances which can increase the concentration of hydroxide (OH) ions in an aqueous solution.

* What is Arrhenius theory?
Ans:
According to Arrhenius theory, acids are substances which liberate H+ ions in aqueous solution and bases are substances which liberate OH- ions in aqueous solutions.

* The equation of a neutralisation reaction is given below...

Ca(OH)₂ + H₂SO₄  ---------> CaSO₄ + 2H₂O

1. Identify the alkali in this reaction?

2. Write down the chemical equation of the reaction between Mg(OH)₂ and HCl

3. Which is the product formed when the common components of an acid combine with the common component of an alkali?

Ans.

1. Ca(OH)₂

2. Mg (OH)₂ + 2HCl  --------> MgCl₂ + 2 H₂O

3. H₂O

* Given below is the equation of a chemical reaction between an acid and an alkali.

Na⁺OH^- + H⁺Cl^-   -------->  NaCl + H₂O

1. Which is the salt formed in this reaction?
2. What is such type of reactions commonly known as ?
2. Name the salt formed when H₂SO₄ is used instead of HCl?
4. Write down the chemical equation of this reaction.

Ans.

1. NaCl

2. Neutralisation

3. Na₂SO₄ (Sodium sulphate)

4. 2NaOH + H₂SO₄ ------------>  Na₂SO₄ + 2H₂O

* Match the columns suitably

A	B	C
Muriate of potash	CaSO4. 2H2O	Fungicide
Blue vitriol	KCl	To control the setting time of cement
Gypsum	CuSO4 .5H2O	Substitute for table salt for B.P patients

Ans. 

A	B	C
Muriate of potash	KCl	Substitute for table salt for B.P patients
Blue vitriol	CuSO4 .5H2O	Fungicide
Gypsum	CaSO4. 2H2O	To control the setting time of cement

* Given below are a few ions 

NH4+, Ca2+ , SO42_

1. Write down the molecular formula of any one compound formed from the given ions.
2. Mention any one use of this salt.

Ans.
1. (NH₄)₂SO₄ / CaSO₄

2. (NH₄)₂ SO₄ - Chemical fertiliser

CaSO_{4 -} To control the setting time of cement.

* The salt (NH4)₂SO4 can be used as chemical fertilizer.

1. Name the cation and anion in this compound.

2. Write down the molecular formulae and chemical name of the compound formed when the anion combines with magnesium ion (Mg²⁺)

Ans.

1. Anion: Sulphate ion

Cation‍ Ammonium ion

2. MgSO₄ - Magnesium sulphate

* The molecular formulae of Sodium sulphate is Na₂SO₄
1. Which is the anion in this compound?
2. Write down the molecular formulae of the compound formed when the anion of sodium sulphate combines with ammonium ion ( NH₄⁺). Mention anyone use of it.
Ans.
1. SO₄^2- / Sulphate ion
2. (NH₄)₂SO₄ chemical fertilizer

* The symbols of a few ions are given in the box

Ca2+, Cl- , NH4 + , SO4 2-

a) Identify the cations.

b) Identify the anions

c) Write down the molecular formulae of all the possible compounds using the given cations and anions.

Ans.

a) Cations

Calcium ion/ Ca ²⁺

Ammonium ion‍/ NH⁴⁺

b) Anions

Chloride ion‍/ Cl^- 

Sulphate ion‍ /SO₄^2- 

c) CaSO₄

CaCl₂

(NH₄)₂SO₄

NH₄Cl

* Analyse the following chemical equation and answer the following question.

H₂SO₄ + Mg(OH)₂ --------> MgSO₄ + 2H₂O

a) Identify the substance which is basic in nature? 

b) Name the salt formed.

c) Name the acid and base which are required to produce potassium nitrate?

Ans.

a) Magnesium hydroxide / Mg(OH)2

b) Magnesium sulphate / MgSO4

c) Acid - Nitric acid/ HNO3

Base - Potassium hydroxide / KOH

* It is necessary to determine the pH of soil before farming. Give the reason for this statement.

Ans.

Determination of pH shows whether the particular soil is acidic or basic in nature. .Based on the PH value suitable crops can be chosen. The PH value of the soil can also be controlled.

* The medicines used to reduce acidity are known as ..............?

(Acids, Antacids, Alkalies, Salts)

Ans. Antacids

* Take some water in a test tube. Pass sulphur dioxide (SO₂ ) gas through it.
a) Dip a blue litmus paper in the solution thus obtained. What do you observe?
b) Write down the chemical equation of the reaction taking place here.

Ans.

a) Blue litmus paper turns red.
b)   SO₂ + H₂O ---------> H₂SO₃

* Match the following. 

A	B	C
Copper sulphate	CaSO4.2H2O	Manufacture of glass
Sodium carbonate	CuSO4.5H2O	A fungicide
Gypsum	Na2CO3.10H2O	Manufacture of cement

Ans.

A	B	C
Copper sulphate	CuSO4. 5H2O	A fungicide
Sodium carbonate	Na2CO3.10H2O	Manufacture of glass
Gypsum	CaSO4.2H2O	Manufacture of cement

* Which one of the following compounds is not used as chemical fertilizer?
[ ( NH₄)₂SO₄, KCl, NaHCO₃, NaNO₃ ]
Ans.
NaHCO₃

* Which of the following compounds is used as chemical fertiliser?

( NaCl , HNO_3, (NH₄)₂SO₄, BaCl₂ )

Ans.

(NH₄)₂SO₄ / Ammonium sulphate

* Molecular the formula of magnesium chloride is MgCl₂

a) Identify the cation and anion and write them

b) What is the valency of magnesium

c) Write down the chemical formula of magnesium oxide if the valency of oxygen is 2

Ans.

a) Cation - Magnesium ion /Mg²⁺

      Anion - Chloride ion‍/Cl^-

b) 2

c) MgO

* When an acid reacts with an alkali, the products obtained are magnesium sulphate and water.

1. Name the acid used in this reaction?

2. Identify the alkali used here?

Ans.

1. Sulphuric acid / H₂SO₄

2. Magnesium hydroxide /Mg(OH)₂

* What is the pH value of water?
( 0, 5, 7, 14 )
Ans. 7
 

* Complete the given chemical equation.

1. NaOH + HCl   ---------->  .................. + ................

2. What is the common name by which this type of reaction known?

3. What is the nature of the substances used to reduce acidity in the stomach. ?

Ans.

1. NaCl    +  H₂O

2. Neutralisation

3. Basic nature

* pH value of some solutions is given in the table. Examine the table and answer the questions

Solution	pH value
A	4
B	7
C	13
D	2
E	8

1. Which one of these represents a neutral solution?

2. Which the solution is more alkaline in nature?

3. Which one of these is more acidic in nature?

4. Give the common name of the reaction in which A and C react together?

Ans.

1. B

2. C

3. D

4. Neutralisation reaction

* Complete the following ionic equations.

a) H₂CO₃  ----------->  ...............  +  CO₃ ^2- 

b) KOH  ------------>   K⁺ +   .............

c) NH₄OH ----------->  ...............  +  OH^-

d) HNO_{3 ---------------->}  H⁺ + ...............

Ans.

a) 2H⁺

b)  OH^-

c) NH₄⁺

d) NO₃^-

a) Which one of the following represents a tribasic acid?

( H₂CO₃, HNO₃, H₃PO₄, HCl, H₂SO₄ )

b) Compete for the following chemical equations.

H₂SO_{4  ------------>}  ...............  + HSO₄^-

HSO₄^-   -----------> H⁺ + ..................

Ans.

a) H₃PO₄

b) H ⁺

SO₄ ^2-

* Given below are the equations of the chemical reaction taking place when Hydrochloric acid dissolves in water. Analyse them and complete the equations.

HCl  ---------------> H⁺ + .................

H⁺ + H₂O ----------> ..................

Ans.

Cl^-

H₃O⁺

a) Classify the following into acidic and basic oxides.

[ CaO, CO₂, MgO, SO_2‍ ]

b) Name the gases found in large quantities in the materials expelled from factories?

c) Which are the acids obtained when these gases dissolve in water?

Ans.

a) Acidic - CO₂, SO₂

    Basic - CaO, MgO

b)  CO₂, SO_2,, NO₂  

c)  Carbonic acid(H₂CO₃), sulphurous acid(H₂SO₃), Nitric acid(HNO₃)

* Take dilute hydrochloric acid in a test tube. Put some calcium carbonate in it.

a) Name the gas produced here?

b) Name the compound formed when this gas gets dissolved in water?

c) Write the balanced chemical equation for the reaction in (b)

Ans.

a) Carbon dioxide

b) Carbonic acid /H₂CO₃

c) CO₂ +   H₂O ---------> H₂CO₃

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