Kerala Syllabus 9th Standard Chemistry Solutions Chapter 5 Acids, Bases, Salts

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Kerala State Syllabus 9th Standard Chemistry Solutions Chapter 5 Acids, Bases, Salts

Acids, Bases, Salts Textual Questions and Answers

Learning Activities

hss live guru 9th chemistry Acids, Bases, Salts Question 1.
What are the methods used to identify acids and alkalies
Answer:
Using indicators like litmus, phenolphthalein and methyl orange.

kerala syllabus 9th standard chemistry chapter 5 Acids, Bases, Salts Question 2.
Find the characteristics of the substances given in the table below using litmus papers.

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

Answer:

Substance	Change in the color 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

class 9 chemistry chapter 5 kerala syllabus Acids, Bases, Salts Question 3.
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.

Answer:
Burn with a ‘pop’ sound

kerala syllabus 9th standard chemistry notes Acids, Bases, Salts Question 4.
What would be the reason?
Answer:
Hydrogen gas liberated burns

kerala syllabus 9th standard chemistry notes chapter 5 Question 5.
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

class 9 chemistry chapter 5 notes kerala syllabus Question 6.
Take some calcium carbonate (marble pieces) in a boiling tube as shown in 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?
Answer:
Carbon dioxide

class 9 chemistry chapter 5 notes Acids, Bases, Salts Ques 7.
What is your observation when this gas is passed through clear lime water?
Answer:
LimeWater turns milky
When acids react with carbonates, carbondioxide(CO₂) gas is liberated.

9th class chemistry chapter 5 Acids, Bases, Salts Question 8.
From the characteristics given below, find out those suitable for acids and put (✓) Mark.
1. Have 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 sour taste
7. Turns red litmus blue
Answer:

1. Have 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 sour taste (✓)
7. Turns red litmus blue

Question 9.
The name of some familiar acids and their chemical formulae are given in the table below. Complete the table.

Answer:

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

Question 10.
Which component is responsible for the common properties of acids
Answer:
H

Question 11.
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?
Answer:
a) H⁺ and Cl^–
b) H⁺ and NO₃^–
c) H⁺

Question 12.
What is acids?
Answer:
Acids are substances which can increase the concentration of hydrogen (H⁺) ions in an aqueous solution.

Question 13.
List the acids that are present in lime juice, curd, tamarind, vinegar.
Answer:
Lime juice — Citric acid
Curd — Lactic acid
Tamarind — Tartaric acid
Vinegar — Acetic acid

Question 14.
Write the chemical equation for the ionization of HCl.
Answer:
HCl → H⁺+Cl^–

Ques 15.
How many hydrogen ions are released when one molecule of HCI is ionized?
Answer:
one H⁺

Question 16.
What is the basicity of an acid?
Answer:
The number of hydrogen ions that can be donated by one molecule of an acid is its basicity.
If the basicity is 1, it is called monobasic acid.

Question 17.
Write the ionization equation of nitric acid (HNO3) and find its basicity.
Answer:
HNO₃ → H⁺ +NO^–₃
Basicity -1

Question 18.
Write the chemical equation for the ionization of the sulphuric acid (H2S04)
Answer:
H2SO₄ → H⁺ + HSO^–₄ (bisulphate ion)
HSO^–₄ → H+ + SO^2–₄ (sulphate ion)

Question 19.
How many hydrogen ions are released when one molecule of H₂SO₄ gets ionized? What is its basicity? ’
Answer:
Two H+ ions basicity = 2
It the basicity of an acid is 2,
it is said to be a dibasic acid.

Question 20.
Complete the ionization equation of phosphoric acid (H3PO4).
H₃PO₄ → ………… + PO^3–₄(Phosphate ion)
Answer:
H₃PO₄ → 3H+ + PO^3–₄ (Phosphate ion)

Question 21.
What is the basicity of H₃PO₄?
Answer:
3
If the basicity is 3,
the acid is called a tribasic acid.

Ques 22.
The chemical formulae of some acids are given in the box. Pick out monobasic and dibasic acids.
H₂CO₃, HNO₃, H₃PO₄, H₂SO₃, HCI, H₂SO₄
Answer:
Monobasic: HNO₃, HCI
Dibasic: H₂CO₃, H₂SO₃, H₂SO₄

Question 23.
How do you make soda water? Write the equation of this reaction.
Answer:
CO₂ is dissolved in water to make soda water.
H₂O + CO₂ → H₂CO₃ (Carbonic acid)

Question 24.
Complete the equation of dissolution of SO₂ in water.
………… + ………….. → H₂SO₃ (sulfurous acid)
Answer:
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.

Question 25.
What is acid rain?
Answer:
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’.

Question 26.
What are the environmental problems caused by acid rain?
Answer:

• 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.

Question 27.
What measures are to be taken against the environmental issues caused by acid rain?
Answer:

• Reduce the excessive use of fossil fuels.
• Before using fossil fuels, remove sulfur compounds from them as far as possible.

Question 28.
Burn a neatly rubbed and cleaned magnesium ribbon. Record the observation. What would be the white powder obtained?
Answer:
Magnesium burns brightly and a white powder is formed. The white powder formed is magnesium oxide (MgO)

Question 29.
Take the product in a watch glass and add two or three drops of water. Find its nature using litmus paper.
Answer:
Red litmus turns to blue. MgO is alkaline in nature.

Question 30.
Write the chemical equation of this reaction.
MgO + H₂O → Mg(OH)₂
magnesium hydroxide

Question 31.
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?
Answer:
a) The solution turns to blue
b) CaO + H₂O → Ca(OH)₂
c) Ca(OH)₂ is alkaline in nature

Question 32.
Are MgO and CaO metallic oxides or non-metallic oxides?
Answer:
Metallic oxides
Metallic oxides generally exhibit characteristics of bases. The bases that dissolve in water are called alkalies.

Question 33.
From the oxides given below, find out the basic oxides. K₂O, SO₂, P₂O₅, MgO, CaO, NO₂
Answer:
Basic oxides- K₂O, MgO, CaO

Question 34.
Chemical names and formulae of some familiar alkalies are given in the table. Complete the table.

Answer:

Chemical name of alkalies	Chemical formula
Sodium hydroxide	NaOH
Calcium hydroxide	Ca(OH)2
Ammonium hydroxide	NH4OH
Potassium hydroxide	KOH

Question 35.
Can you find out the common factor in alkalies?
Answer:
OH

Bases and alkalies:
All bases are not alkalies. Water-soluble bases are called alkalies.
NaOH and KOH are alkalies. But even though Al(OH)₃ and Cu(OH). are based, they are not considered as alkalies as they are not soluble in water. Metallic oxides are generally basic in nature. But a few of them have both acidic as well as basic character. Such oxides are called amphoteric oxides. Example Al,O₃, ZnO
They can react with acids as well as bases.

Question 36.
Write the equation of the dissolution of sodium hydroxide in water.
Answer:
NaOH → Na⁺ +OH^– (hydoxide ion)

Question 37.
Complete the given equation of the ionization of calcium hydroxide.
Ca(OH)₂ → Ca⁺₂ +……….
Answer:
Ca(OH)₂→ Ca⁺₂ + 2OH^–

Question 38.
Which is the common ion released when alkalies dissolve in water?
Answer:
OH-
Alkalies are substances which can increase the concentration of hydroxide (OH) ions in anaqueous solution.

Question 39.
Write common names of some alkalies, their chemical names and chemical formulae
Answer:

Question 40.
The equations representing the ionization of some acids and alkalies are given below. Fill in the blanks.
Answer:
HCl → H⁺ + Cl^–
KOH → K⁺ +OH^–
H₂CO₃ → 2H⁺ + CO₃^2-
NH₄OH → NH⁺₄ + OH^–
HNO₃ → H⁺ + NO^–₃

Question 41.
What is Arrhenius theory?
Answer:
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.

Question 42.
What was the color of NaOH solution when phenolphthalein was added?
Answer:
Pink

Question 43.
Which nature of the NaOH solution is indicated here?
Answer:
Alkaline

Question 44.
What do you infer from the decrease in the intensity of colour of the NaOH solution on adding HCl?
Answer:
Concentration of NaOH is decreasing

Question 45.
When the color disappears completely will there be any NaOH left behind in the conical flask?
Answer:
No

Question 46.
Add a few drops of NaOH solution to the completely decolorized. What change can you observe? What will be the reason?
Answer:
Pink color reappears concentration of NaOH in-creases.

Question 47.
To this again add dilute HCl drop by drop and stir it. What do you observe?
Answer:
Pink color disappears

Question 48.
What are neutralization reactions?
Answer:
Acid and alkali react with each other to nullify their individual properties. Such chemical reactions are called neutralization reactions.

Question 49.
Write the chemical equation for the neutralization reaction between sodium hydroxide and dilute hydrochloric acid.
Answer:
NaOH + HCI → NaCI + H₂O

Question 50.
You have already recorded the volume of HCI used for neutralization of 20 mL NaOH in the earlier experiment. Change the concentration of the acid and repeat the experiment. Is there any change in the volume of HCI?
Answer:
Yes

Question 51.
Can you find out more examples for neutralization reaction?
Answer:

• Slaked lime is sprinkled in farms to reduce acidity
• Antacids are used to remove acidity in the stom¬ach.

Question 52.
What happens when the acid level in the stomach is high?
Answer:
It increases the acidity of the stomach

Question 53.
What do we do in such situations?
Answer:
We take antacids.

Question 54.
What are antacids?
Answer:
The medicines used for reducing acidity in the stomach are known as antacids.

Question 55.
What types of substances are present in antacids?
Answer:
Alkaline

Question 56.
How do they work?
Answer:
They neutralize acid in the stomach.

Question 57.
Take equal quantities of dilute hydrochloric acid, sodium hydroxide solution and distilled water in three test tubes. Use red litmus paper and blue litmus paper to find out the nature of the solutions. Also, add two or three drops of phenolphthalein solution to the three test tubes. Record the observation and find out the nature of the substances.
Do you notice any color change in distilled water? What property of water is revealed here?
Answer:
No’, water is neutral

Question 58.
What happens to the amount of H⁺ ions when a little acid is added to water?
Answer:
Increase

Question 59.
What happens if alkali is added?
Answer:
Amount OH^– increases

Question 60.
What is pH value?
Answer:
Determination of pH value is the scientific method for finding the acidic/alkaline nature of substances. The Danish scientist Sorensen devised the pH scale for this. The pH scale was devised based on the H⁺ ion concentration in the solution.

Question 61.
Observe the pH scale and answer the questions given below. What is the pH value of the neutral solution?

Answer:
7

Question 62.
What is the nature of the solution having pH value more than 7?
Answer:
Basic

Question 63.
What is the nature of the solution having pH value less than 7?
Answer:
Acidic

Question 64.
What is pH scale?
Answer:
The pH scale is the method used to express the acidic /basic nature of a substance based on the amount of H ions present in their aqueous solutions.
On the basis of the pH scale, the pH value of a neutral solution is 7. The pH value of acids is less than

Question 65.
How the pH value can be find out using pH solution?
Answer:
Add a drop of pH solution to the solution whose pH is to be determined or dip the pH paper into it. The pH value of the solution can be determined by comparing with the pH color chart.

Question 66.
Find the pH value of the following substances using the pH paper and complete the table given below.

Answer:

Name of Substance	colour of pH paper	pH value	acid/ base
Vinegar	Red	less than 7	Acid
Lime water	Blue	more than 7	base
dil. Hydro­chloric acid	Red	less than 7	Acid
Water	no colour change	7	neutral
Washing soda Solution	Blue	more than 7	base
Ammonia Solution	Blue	more than 7	base
Potassium nitrate solution	no colour change	7	neutral
Sodium chloride solution	no colour change	7	neutral

Question 67.
It is better to determine the pH of soil before farming? Why?
Answer:
The pH of soil is an important factor for crops. It is important to identify whether the soil of a region is suitable for a particular crop. Acidic soil is suitable for some crops while basic soil for a few others.

Question 68.
What are the products of the reaction between dilute hydrochloric acid and sodium hydroxide solution?
Answer:

Question 69.
Name the products formed when the common component of an acid and the common component of an alkali combine together.
Answer:
H₂O (water)

Question 70.
Which is the positive ion present in sodium hydroxide? Which is the negative ion present in hydrochloric acid?
Answer:
Na+ Cl^–

Question 71.
Write the chemical formula of the compound formed by the combination of these two ions. Identify this substance.
Answer:
Na+ + Cl → NaCI

Question 72.
What is naturalization?
Answer:
Neutralization is the process in which acid and alkali react with each other to form salt and water. Acid + Alkali → Salt + water

Question 73.
Complete the equation for the reaction between dilute sulphuric acid (H2S04) and magnesium hydrox¬ide Mg(OH)2.
Mg(OH)₂ + H₂SO₄ → + 2H₂O
Answer:
Mg(OH)₂ + H₂SO₄ MgSO₄ + 2H₂O

Question 74.
What are the products formed?
Answer:
Magnesium sulfate (MgSO₄) and water (H₂O)

Question 75.
Identify the salts given in the table and find out the acids and alkalies required for the formation of salt

Answer:

Salt	Chemical formula	Acid	Alkali
Magnesium chloride	MgCl2	HCI	Mg(OH)2
Calcium sulphate	CaSO4	H2SO4	Ca(OH)2
Aluminium sulphate	Al2(SO4)3	H2SO4	Al(OH)3
Sodium nitrate	NaNO3	HNO3	NaOH
Potassuim ‘ phosphate	K3PO4	H3PO4	KOH

Question 76.
Write the name and symbol of some positive ions and negative ions.
Answer:

Question 77.
Write the name and symbol of some positive ions and negative ions.
Answer:
Formula — Name
KOH — Potassium hydroxide
K₂CO₃ — Potassium carbonate
KHCO₃ — Potassium bicarbonate
KNO₃ — Potassium nitrate
K₂SO₄ — Potassium sulphate
KHSO₄ — Potassium bisulphate
K₃PO₄ — Potassium phosphate
KH₂PO₄ — Potassium dihydrogen phosphate
Zn(OH)₂ — Zinc hydroxide
ZnCO₃ — Zinc carbonate
Zn(HCO₃)₂ — Zinc bicarbonate
Zn(NO3)2 — Zinc nitrate
ZnSO₄ — Zinc sulfate
Zn(HSO₄)₂ — Zinc bisulfate
Zn₃(PO₄)₂ — Zinc phosphate
Zn(H₂PO₄)₂ — Zincdihydrogen phosphate
Fe(OH)₂ — Ferrous hydroxide
FeCO₃ — Ferrous carbonate
Fe(HCO₃)₂ — Ferrous bicarbonate
Fe(NO₃)₂ — Ferrous nitrate
FeSO₄ — Ferrous sulfate
Fe(HSO₄)₃ — Ferrous bisulfate
Fe₃(PO₄)₂ — Ferrous phosphate
Fe(H₂PO₄)₂ — Ferrous dihydrogen phosphate
Fe(OH)₃ — Ferric hydroxide
Fe₂(CO₃)₃ — Ferric carbonate
Fe(HCO₃)₃ — Ferric bicarbonate
Fe(NO₃)₃ — Ferric nitrate
Fe₂(SO₄)₃ — Ferric sulphate
Fe(HSO₄)₃ — Ferric bisulphate
FePO₄ — Ferric phosphate
Fe(H₂PO₄)₃ — Ferric dihydrogen phosphate
CuOH — Cuprous hydroxide
Cu₂CO₃ — Cuprous carbonate
CuHCO₃ — Cuprous bicarbonate
CuNO₃ — Cuprous nitrate
Cu₂SO₄ — Cuprous sulphate
CuHSO₄ — Cuprous bisulphate
Cu₃PO₄ — Cuprous phosphate
CuH₂PO₄ — Cuprous dihydrogen phosphate
Cu(OH)₂ — Cupric hydroxide
CuCO₃ — Cupric carbonate
Cu(HCO₃)₂ — Cupric bicarbonate
Cu(NO₃)₂ — Cupric nitrate
CuSO₄ — Cupric sulphate
Cu(HSO₄)₂ — Cupric bisulphate
Cu₃(PO₄)₂ — Cupric phosphate
Cu(H₃PO₄)₂ — Cupric dihydrogen phosphate
NHOH — Ammonium hydroxide
(NH₄)₂CO₃ — Ammonium carbonate
NH₄HCO₃ — Ammonium bicarbonate
NH4NO3 — Ammonium nitrate
(NH₄)₂SO₄ — Ammonium sulphate
NH₄HSO₄ — Ammonium bisulfate
(NH₄)₃PO₄ — Ammonium phosphate
NH₄H₂PO₄ — Ammonium dihydrogen phosphate
Mn(OH)₂ — Manganous hydroxide
MnCO₃ — Manganous carbonate
Mn(HCO₃)₂ — Manganous bicarbonate
Mn(NO₃)₂ — Manganous nitrate
MnSO₄ — Manganous sulfate
Mn(HSO₄)₂ — Manganous bisulfate
Mn₃(PO₄)₂ — Manganous phosphate
Mn(H₂PO₃)₃ — Manganous dihydrogen phosphate

Question 78.
The name of few salts and their chemical formulae are given in the table. Complete the table adding names of more salts and write the positive ions and negative ions.

Answer:

Nameof salt	Chemical formula	Positive ion	Negative ion
Sodium Chloride	NaCl	Na+	Cl–
Magnesium sulphate	MgSO4	Mg2+	SO42–
Calcium carbonate	CaCO3	Ca2+	CO32–
Sodium nitrate	NaNO3	Na+	NO5
Aluminium sulphate	Al2(SO4)3	Al3+	SO42–

Question 79.
What is the number of positive ions and negative ions in a ‘molecule’ of NaCI?
Anaswer:
Positive ions 1, Negative ions 1

Question 80.
What would be the sum of the charges of the posi¬tive ions and negative ions in a ‘molecule’ of NaCI?
Answer:
1⁺ + 1^– = 0 (zero)

Question 81.
Why slats are neutral in nature?
Answer:
Salts are electrically neutral. The sum of the charge of the positive ions and negative ions in a salt will be zero.

Question 82.
What are the method of writing chemical formulae of salts?
Answer:

• While writing the chemical formula, first write the symbol of the positive ion and then the symbol of the negative ion.
• Write the numbers indicating the charge of each ion as subscripts after interchanging them.
• Simplify the subscripts and write them in the smallest whole-number ratio.

Question 83.
Write the different stages in writing the chemical formulae of compounds formed by the combination of magnesium ion (Mg³⁺) with phosphate ion (PO₄³-) and carbonate ion (CO₃²-)
Answer:
Mg²⁺ PO₄³–
Mg²⁺CO₃²–
Mg₃ (PO₄)₂
Mg_2/2 (CO₃)_2/2
MgCO₃

Question 84.
Some positive ions and negative ions are given in the table. Write the name and chemical formulae of the maximum possible salts formed by them.
Positive ion — Negative ion
Ca²⁺ (calcium ion) — Cl^– (chloride ion)
NH₄⁺ (Ammonium ion) — SO₄²– (sulphate ion)
PO₄³– (Phosphate ion)
Answer:
1) Calcium chloride CaCl₂?
2) Calcium sulphate CaSO₄
3) Calcium phosphate Ca₃(PO₄)₂
4) Ammonium chloride NH₄Cl
5) Ammonium sulphate (NH₄)2SO₄
6) Ammonium phosphate (NH₄)3PO₄

Question 85.
Give example for some salts that are used as fertilizers.
Answer:

• Ammonium sulphate.(NH₄)₂SO₄
• Potassium chloride KCl
• Sodium nitrate NaNO₃

Question 86.
We use various salts in our daily life. A list of some of these salts and their chemical formulae are given in the table. Analyze the table and complete.

Answer:

Let Us Assess

Question 1.
Complete the chemical equations for the following ionization equation.

Answer:

Question 2.
Identify the symbol from the box and write against their names.
SO₃²– , NO₃^– , HCO₃^–, OH^–, CO₃²-, HSO₄^–
Carbonate —
Bisulphate —
Sulfite —
Nitrate —
Hydroxide —
Bicarbonate —
Answer:
Carbonate → CO₃²–
Bisulphate → HSO₃^–
Sulfite → SO₃²–
Nitrate → NO₃
Hydroxide → OH^–
Bicarbonate → HCO₃

Question 3.
a) Name the salt formed by the reaction between
magnesium hydroxide [Mg(OH)₂] and dil. hydrochloric acid (HCl).
b) Write the equation for the reaction
c) Which is the acid required for the preparation of magnesium sulfate?
Answer:
a) Magnesium Chloride
b) Mg(OH)₂ + 2HCl MgCl₂ + 2H₂O
c) H₂SO₄ (sulphuric acid)

Question 4.
List the cation and anions of the substance given in the table.

Answer:

Compound	Chemical formula	Cation	Anion
Potasium Chloride	KCl	K+	Cl–
Magnesium Chloride	MgCl2	Mg2+	Cl–
Sodium Nitrate	NaNO3	Na+	NO3–
Ammonium Chloride	NHCl4	NH4+	Cl–
Aluminium Sulphate	Al2(SO4)3	Al3+	C042–
Calcium Phosphate	Ca(PO4)3	Ca2+	PO43–

Question 5.
A little distilled water is taken in a beaker.
A. What is the pH value of the distilled water?
B. What happens to the pH value when the following substances are added to the water? Justify your answer.
i) Caustic soda
ii) Vinegar
Answer:
A. Seven
B. i) pH value increases, solution becomes basic
ii) pH value decreases, solution becomes acidic

Question 6.
Match the column A, B, and C by identifying the correct chemical formulae and the use of the salts

Answer:

Salt	Chemical	Use
Washing soda	Na2CO3.10H2C	Manufacture of Glass
Gypsum	CaSO4.2H2O	Manufacture of cement
Blue vitriol	CuSO4.5H2O	Fungicide
Baking soda	NaHCO3	Fire extinguisher

Question 7.
The pH values of some substances are given in the table. Analyze the table and answer the questions

Substance	pH value
Vinegar	4.2
Limewater	10.5
Milk	6.4
Water	7
Toothpaste	8,7
Blood	7.36

a. Is blood acidic or basic in nature?
b. The pH value of pure milk is 6.4. Does the pH value increase or decrease when milk changes . to curd. Justify your answer
c. Among the substances given in the above table
(i) Which one is strongly basic?
(ii) Which one has weak acidic nature
Answer:
a) Basic
b) pH value decrease. Curd is lactic acid
c) i) Limewater
ii) Blood

Extended Activities

Question 1.
Organic acids are present in a number of substances we use in our daily life.
(eg. Tomato, orange, apple, grapes, curd, etc.) Identify the organic acids in each of them and tabulate.
Answer:
Tomato — oxalic acid
Orange — Citric acid
Apple — Malic acid
Grapes — Tartaric acid
Curd — Lactic acid, Butiric acid

Question 2.
Haven’t you conducted an activity to find the pH value of the soil related to different crops? Identify the pH values of soil samples collected from different places.
Prepare a list of the crops that are suitable for the soil of each area on the basis of its pH value
Answer:

Name of crop	Suitable pH
Paddy	5-8
Coconut	5-8
Rubber	5-6.5
Tea	4.0-6.5
Coffee	4.5-5.5
Potato	5.2-7.5
Cocoa	5.5-7.0
Tobacco	5.5-6.00
Brinjal	5.5-6.50
Cucumber	6.0-7.5
Bitter gourd	6.0-7.5
Watermelon	6.5-70
Tapioca	5.5-7.0

Question 3.
a) Complete the equations of the ionization of phosphoric acid.
H₃PO₄ → H⁺ + H₂PO₄^– (Dihydrogenphosphate ion)
H₃PO₄^– → H+ + …………. (Hydrogenphosphate ion)
…….. → H⁺ + PO₄^3- (phosphate ion)
b) How many types of salts can be formed by phosphoric acid? Why?
c) Write the chemical name of the following salts.
Mg(H₂PO₄)₂
MgHPO₄
Mg₃(PO₄)₂
Answer:
a) H₂PO₄^– → H⁺ + HPO₄^2- (Hydrogenphosphate ion)
HPO₄^2- → H^– + PO₄^3- (phosphate ion)
b) It is tribasic
c) Magnessium dihydrogen phosphate Magnessium hydrogenphosphate Magnessium phosphate

Question 4.
Solution of sodium carbonate, potassium chloride, and ammonium sulfate are taken in separate beakers. Dip a litmus paper (red, blue) in each beaker.


Answer:

Salt	Colour of the litmus paper	Nature of the substance
A	Red litmus turns	Basic
	to blue
B	No color change	Neutral
C	Blue litmus turns to red	Acidic

i) Observe the color change of litmus paper and tabulate.
ii) Name the acid and alkali that react to form each salt given above?
iii) Can you explain the color change of the litmus paper on the basis of the nature of the acid and alkali that react to form the salt?
(hint: Potassium chloride is a salt formed by the reaction between a strong acid and a strong alkali)

i) Salts formed by the reaction between a strong acid and a strong base will be neutral in nature, eg: KCI
ii) Salts formed by the reaction between a strong base and weak acid will be slightly basic eg: Na2CO3
iii) Salts formed by the reaction between a weak base and strong acid will be slightly acidic eg:(NH4)2SO4

Acids, Bases, Salts More Questions and Answers

Question 1.
Non-metalic oxides like CO₂, SO₂, and NO₂ shows acidic nature, justify it.
Answer:
Compounds formed by the reaction of the above nonmetal oxide dissolves in water shows acidic character.

Question 2.
Take quick lime (Calcium oxide) in a beaker containing water. Take a little of this in a test tube and show a red litmus paper.
Answer:
Red litmus paper turns to blue because calcium oxide dissolves in water to form calcium hydroxide. It is basic in nature.

Question 3.
Complete the equation of the reaction between calcium oxide and water.
Answer:
CaO + H₂O → Ca(OH)₂

Question 4.
What can be inferred about the nature of this substance from the litmus test?
Answer:
Alkaline nature

Question 5.
Classify the following oxides into acidic oxide and basic oxide
SO₃, NO₂, CaO, K₂O P₂O₅, Na₂O, CO₂, MgO
Answer:

Acidic Oxide	Basic Oxide
SO3	Cao
NO2	K2O
P2O5	Na2O
CO2	MgO

Question 6.
Try to write the chemical equation for the reaction of Fe with hydrochloric acid.
Answer:
Fe + 2 HCI → FeCl₂ + H₂

Question 7.
Analyze the chemical equation for the reactions taking place when hydrochloric acid dissolves in water.
Answer:
HCl → H⁺ + Cl^–
H⁺ + H₂O → H₃O⁺ (Hydronium ion)

Question 8.
Explain the basis of classification of acid into monobasic, Dibasic and tribasic acids.
Answer:
An acid molecule dissolves in water to liberate H⁺ ions. Based on this acids are classified into monobasic, Dibasic and tribasic acids. HCl is a monobasic acid.

Question 9.
Explain the dissociation of H2SO4
Answer:
H₂SO₄ → H⁺ + HSO₄⁺ (Bisulphate ion)
HSO₄– → H⁺ + SO₄²⁺ (Sulphate ion)

Question 10.
Classify the following acids into monobasic, dibasic and tribasic acids,
H₂CO₃, HNO₃, H₃PO₄, H₂SO₄, HCl, H₂S₄
Answer:

Question 11.
During the rainy season, the farmers are using slaked lime in agricultural fields, give reason.
Answer:
To reduce the acidity of the soil.

Question 12.
Write the chemical formula of slaked lime.
Answer:
Calcium hydroxide – Ca(OH)₄

Question 13.
Most of the alkalies are also known by the common names in addition to their chemical names. Caustic soda, milk of lime, milk of magnesia and caustic potash are the common names of some alkalies. Identify the chemical formula with the help of the given table.
Answer:

Question 14.
Observe the chemical equation of the dissolution of Sodium hydroxide in water.
NaOH → Na⁺ + OH^– (Hydroxide ion)
Now complete the given chemical equation for the ionization of Calcium hydroxide.
Ca(OH)2 → + ………. + …………..
Answer:
Ca(OH)₂ → Ca⁺ + 2OH^–

Question 15.
Which is the common ion released when alkalies dissolved in water?
Answer:
OH^–

Question 16.
Difference between bases and alkalies?
Answer:
Bases are compounds that are opposite in acids in their characteristics.
Bases dissolving in water are alkalies. The metal hydroxide which dissolves in water functioning as strong alkalies.
Sodium hydroxide, Potassium hydroxide are alkalies, but Al(OH)₃, Ca(OH)₂ are bases.

Question 17.
What is meant by a neutralization reaction?
Answer:
An acid combines with alkali to nullify their individual properties. Such reactions are called neutralization reaction.

Question 18.
Give equation for the neutralization reaction of Sodium hydroxide with Hydrochloric acid.
Answer:
NaOH + HCl → NaCl + H₂O

Question 19.
If we add small quantity of acid to water, what happens to the quantity of H⁺ ion?
Answer:
Quantity of H⁺ ion increases.

Question 20.
What change occurs when alkali is added?
Answer:
Quantity of OH⁺ ion increases.

Question 21.
Complete the table and find the pH value by using pH paper of the following substances.
Answer:

Question 22.
If the pH value increases whether acid or alkali character increases?
Answer:
Alkali character increases

Question 23.
If the pH value increases whether the H⁺ ion concentration decreases or increases?
Answer:
Decreases

Question 24.
The names of a few salts and their chemical formulas are given below. Find the cations & anions and complete the table.
Answer:

Question 25.
Can you find out the acid and alkali responsible for the formation of the salts given in the table from their chemical formula
Answer:

Question 26.
Prepare a table by writing the chemical formula of more salts that you are familiar with and also the names of the acid and alkalies from which they are formed.
Answer:

Question 27.
Find out how the chemical formula of the salts are written analyzing the table.
Answer:

Question 28.
Give the salts used as chemical fertilizers?
Answer;
Ammonium Sulphate – (NH₄)₂SO₄
Potassium Chloride – KCl
Sodium Nitrate – NaNO₃

Question 29.
a) Complete the chemical equation for the ionization of Phosphoric acid.
H₃PO₄ → H⁺ + H₂PO₄⁺
H₃PO₄⁺ → H+ + ……….
………. → H⁺ + PO₄^3-
b) Based on the ionization equation given above Phosphoric acid is a tribasic acid? Justify it.
Answer:
a) H₃PO₄ → H⁺ + H₂PO₄^2-(Dihydrogen Phosphate ion)
H₂PO₄^– → H⁺ + HPO₄^2- (Hydrogen Phosphate ion)
HPO₄^2- → H⁺ + PO₄^3- (Phosphate ion)
b) In Phosphoric acid in aqueous solution number of H⁺ ion release is 3. Hence it is a tribasic acid.

Question 30.
Two solutions A and B having pH value 5 and 9, respectively. Which one shows acidic character and which one shows alkaline character. Why?
Answer:
A shows acidic character because the pH value is below 7, B shows alkaline character because the pH value is above 7.

Question 31.
List the cations and anions of the substances given in the table.

Answer:

Substance	Chemical formula	Anion	Cation
Potassium Sulphate	K2SO4	SO42–	Mg2+
Ammonium Nitrate	NH4NO3	NO31-	NH4+
Calcium Chloride	CaCl2	Cl–	Ca2+
Magnesium Carbonate	MgCO3	CO32–	Mg2+

Question 32.
Some cations and anions are given. Write the chemical formula of all the salts possible by combining them.

Answer:

Question 33.
Name the salt formed by the reaction between Potassium hydroxide (KOH) and Nitric acid (HNO₃).
Answer:
a) Potassium Nitrate
b) KOH + HNO₃ → KNO₃ + H₂O