KSEEB Solutions for Class 10 Science Chapter 2 Acids, Bases and Salts

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Karnataka State Syllabus Class 10 Science Chapter 2 Acids, Bases and Salts

KSEEB Class 10 Science Acids, Bases and Salts Intext Questions and Answers

Question 1.
You have been provided with 3 test tubes. One of them contains distilled water and the other two contains an acidic solution and a basic solution, respectively. If you are given only red litmus paper how will you identify reacts with acid the contents of each test tube?
Answer:
Mark A, B, C on the test tubes. Put red litmus in each test tube. If there is no change in test tube it is acid, if litmus changes to blue it is an acid, if there is little change in litmus it is distilled water.

Question 2.
Why should curd and sour substances not be kept in brass and copper vessels?
Answer:
Curd and other sour substances should not be kept in brass and copper vessels. This is because curd and other sour substances contains acids which can react with these can cause food poisoning and damage health.

Question 3.
Which gas is usually liberated when an acid reacts with a metal? Illustrate with an example. How will you test the presence of this gas?
Answer:
When a metal react with an acid usually hydrogen gas is liberated. For example zinc reacts with dil. Sulphuric acid as follows:
Zn + H₂SO₄ → ZnSO₄ + H₂Zinc + sulphuric → Zinc sulphate + Hydrogen acid
The hydrogen gas evolved can be tested by passing the gas through soap solution and thus bringing a burning candle near the soap bubble filled with the gas. The soap bubble bursts and the hydrogen gas burns with a pop sound.

Question 4.
Metal compound A reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride.
Answer:
The gas that extinguishes a burning candle is carbon dioxide. It is formed by the action of dilute HCl on a metal carbonates or metal hydrogen carbonate and produces effervescence since one of the compounds formed is calcium chloride. This shows that the metal compound is calcium carbonate. It cant be calcium hydrogen carbonate because calcium hydrogen carbonate is found in solution. Thus, the metal compound A is calcium carbonate (CaCO₃). Calcium carbon at reacts with dil HCl to form calcium chloride, CO₂ and water. CaCO₃ (s) + 2HCl(aq) → CaCl₂(aq) + CO₂(g) + H₂O(I)

Question 5.
Why do HCl, HNO₃, etc show acidic character in aqueous solutions while solutions of compounds like C₂H₅OH and glucose do not show acidic character?
Answer:
HCl, HNO₃, etc ionise in the aqueous solutions to produce H⁺ ions. Hence they show acidic character compounds like C₂H₅OH and glucose do not ionise in the aqueous saturation to give H⁺ions. i,e hydrogen present in them in non ionisable. Hence, they do not show acidic character.

Question 6.
Why does an aqueous solution of an acid conduct electricity?
Answer:
An acid in the aqueous solution ionises to produce. H⁺ ions and the corresponding negative ions.
For ex : HCl gives H⁺ and Cl^–ions. Due to the presence of ions in the solution, it conducts electricity.

Question 7.
Why does dry HCl gas not change the colour of the dry litmus paper?
Answer:
Dry HCl gas does not change the colour of dry litmus paper because it has no hydrogen ions (H⁺) in it.

Question 8.
While diluting an acid why is it recommended that the acid should be added to water and not water to the acid?
Answer:
Dilution of concentrated acid with water is a highly exothermic process. If water is added into acid, the heat produced is so large that the solution may splash out and the beaker in which it is carried out may break due to excessive heating. Hence dilution is done by adding acid into water.

Question 9.
How is the concentration of hydronium ions (H₃O⁺) affected, when a solution of an acid is diluted?
Answer:
When a solution of an acid is diluted the concentration of hydroxonium ions H₃O⁺ per unit volume decreases.

Question 10.
How is the concentration of hydroxide ions (OH^–) affected, when excess base is dissolved in a solution of sodium hydroxide?
Answer:
On dissolving excess base in a solution of sodium hydroxide, the concentration of OH^– ions per unit volume in the solution increases.

Question 11.
You have two solutions A and B. The pH of the solution a is 6 and pH of a solution of B is 8. Which solution has more hydrogen ion concentration? Which of this is acidic and which one is basic?
Answer:
The pH of a solution is inversely proportional to its hydrogen ion concentration This means that the solution having lower pH will have more hydrogen ion concentration. Thus solution A will have more hydrogen ion concentration.
\(\mathrm{pH} \propto \frac{1}{\text { Hydorgen ion concentration }}\)
A solution with pH < 7 is acidic. Hence solution A is acidic. A solution with pH >7 is basic. Hence solution B is basic.

Question 12.
What effect does the concentration of H⁺ (aq) ions have on the acidic nature of the solution.
Answer:
Water contains exactly the same number of H⁺ and OH^– ions. Acidic solution contains more hydrogen ions than water. Higher the concentration of H⁺ ions in a solution, more acidic is the solution.

Question 13.
Do Basic solutions also have H⁺ (aq) ions. If yes then why are these basic?
Answer:
Basic solution also have H⁺ ions in addition to OH⁺ ions. They are basic because in these solutions OH ion concentration is greater than H⁺ ion concentration.

Question 14.
Under what soil condition do you think a farmer would treat the soil of his field with quick lime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (Calcium carbonate)?
Answer:
Mast of the plants grow best when the pH of the soil is close to 7. If the soil is too acidic or too basic the plants grow badly or do not grow at all. As quick lime, slaked lime or chalk are all alkaline substances, these would be added to the soil by the farmer when soil is highly acidic.

Question 15.
What is the common name of the compound CaOCl₂?
Answer:
Bleaching powder

Question 16.
Name the substances which on treatment with chlorine yields bleaching powder?
Answer:
Dry slaked lime Ca(OH)₂

Question 17.
Name the sodium compound which is used for softening hard water?
Answer:
Washing soda (Sodium Carbonate)

Question 18.
What will happen if a solution of sodium hydrogen carbonate is Heated? Give the equation of the
reaction involved?
Answer:

Sodium hydrogen carbonate on heating decomposes to give sodium carbonate, carbon dioxide and water.

Question 19.
Write an equation to show the reaction between plaster of paris and water?
Answer:
Plaster of paris (CaSO₄\(\frac{1}{2}\)H₂O) on mixing with water changes into gypsum
(CaSO₄2H₂O) which sets to a hard mass in about half an hour.

KSEEB Class 10 Science Acids, Bases and Salts Textbook Exercise Questions and Answers

Question 1.
A solution turns red litmus blue, its pH is likely to be
(a) 1
(b) 4
(c) 5
(d) 10
Answer:
(d) 10

Question 2.
A solution reacts with crushed eggshells to give a gas that turns lime – water. The solution contains
(a) NaCl
(b) HCl
(c) LiCl
(d) KCl
Answer:
(b) HCl

Question 3.
10 mL of a solution of NaOH is found to be completely neutralised by 8 mL of a given solution of HCl. If we take 20 mL of the same solution of NaOH, the amount HCl solution (the same solution as before) required to neutralise it will be
(a) 4 mL
(b) 8 ML
(c) 12 mL
(d) 16 mL
Answer:
(d) 16mL

Question 4.
Which one of the following types of medicines is used for treating indigestion?
(a) Antibiotic
(b) Analgestic
(c) Antacid
(d) Antiseptic
Answer:
(c) Antacid

Question 5.
Write word equations and then balanced equations for the reaction taking place when
(a) dilute sulphuric acid reacts with zinc granules.
(b) dilute hydrochloric acid reacts with magnesium ribbon.
(c) dilute sulphuric acid reacts with aluminium powder.
(d) dilute hydrochloric acid reacts with iron filings.
Answer:
(a) Zinc + dilute sulphuric acid → Zinc sulphate + Hydrogen
Zn + H₂SO₄ → ZnSO₄ + H₂

(b) Magnesium ribbon+dil hydrochloric acid → Magnesium chloride + Hydrogen
Mg + 2 HCl → MgCl₂ + H₂

(c)

(d) Dil hydrochloric acid + Iron filings → Iron chloride + Hydrogen
2 Fe + 6 HCl → 2 Fecl₃ + 3 H₂

Question 6.
Compounds such as alcohols and glucose also contain hydrogen but are not categorised as acids. Describe an activity to prove it.
Answer:
Take solutions of alcohols, glucose in a beaker. Take a cork and fix two nails on the cork upto the end. Keep this cork in the beaker. Connect the nails to two terminals of a 6-volt battery through a bulb and a switch, switch on the current. You will see that bulb does not glow or the current does not pass through the circuit. This means no ions or H⁺ ions are present in the solution. This shows that alcohols and glucose are not acids.

Question 7.
Why does distilled water not conduct electricity, where as rain water does?
Answer:
Rain water contains ions of acids and so it conducts electricity where as there are no ions in distilled water.

Question 8.
Why do acids not show acidic behaviour in the absence of water?
Answer:
Acids in water give hydronium ions which are responsible for their acidic behaviour. But in the absence of water acids do not generate hydronium ions and thus do not show acidic behaviour.

Question 9.
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
(a) Neutral?
(b) Strongly alkaline?
(c) Strongly acidic
(d) Weakly acidic?
Weakly alkaline?
Answer:
(a) D (b) C (c) B (d)A (e) E
11< 9 < 7< 4 < 1 → pH values in increasing order of hydrogen ion concentration.

Question 10.
Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCl) is added to test tube A, while acetic add (CH₃COOH) is added to test tube B, Amount and concentration taken for both the acids are same. In which test tube will the fizzing occur more vigorously and why?
Answer:
Fizzing occurs more vigorously in the test tube containing HCl because HCl is a strong acid comparing to CH₃COOH. Hydrogen gas is liberated with fizzing.

Question 11.
Fresh milk has a pH of 6. How do you Why does distilled water not conduct electricity, where as rain water does?
Answer:
pH of milk falls below 6 as it turns into curd due to the formation of lactic acid during this process.

Question 12.
A milkman adds a very small amount of baking soda to fresh milk.
(a) Why does he shift the pH of the fresh milk from 6 to slightly alkaline?
(b) Why does this milk take a long time to set as curd?
Answer:
(a) The milk man adds a little baking soda to fresh milk to make it slightly alkaline so that it can be preserved for a longer time.
(b) Initially, lactic acid formed is used upto neutraline the base i.e baking soda and when more lactic acid is formed, the milk sets as curd.

Question 13.
Plaster of Paris should be stored in a moisture-proof container. Explain why?
Answer:
Plaster of Paris is calcium sulphate hemidydrate (CaSO₄\(\frac{1}{2}\)H₂O) on exposure to moisture it absorbs moisture and becomes gypsum (CaSO₄ 2H₂O) which does not have the required setting property.

Question 14.
What is a neutralisation reaction? Give two examples.
Answer:
The reaction between an acid and a base to give salt and water is known as a neutralisation reaction.
Base + acid → Salt + Water
Ex:

Question 15.
Give two important uses of washing soda and baking soda.
Answer:
Uses of baking soda

It is used in bakery.
It is used in soda acid fire extinguishers

Uses of Washing soda

It is used in the manufacture of glass, soap and paper.
It is used for removing permanent hardness of the water.

Fill in the blanks:

Question 1.
Indicators like litmus, phenolphthalein, methyl orange etc are called …………….. indicators
Answer:
Acid – base

Question 2.
……………… gas is generally evolved when a metal is dropped into a dilute acid
Answer:
H₂

Question 3.
gas is evolved when metal carbonate reacts with acids.
Answer:
CO₂

Question 4.
Non – metallic oxides are ……………… because these react with a base to give salt and water.
Answer:
Acidic

Question 5.
All acids produce ……………… ions in water.
Answer:
H⁺

Question 6.
The process of dissolving an acid or a base in water is a highly ……………… process.
Answer:
Exothermic

Question 7.
The strength of a base is measured by the no. of ……………… ions it produces in a solution.
Answer:
OH^–

Question 8.
The irritation and pain due to indigestion can be reduced by using substances called ………………………..
Answer:
Antacids

Question 9.
Important chemicals like Cl₂, H_2, and NaOH are obtained by elector lysis of ………………………..
Answer:
NaCl

Question 10.
All soluble hydroxides are ………………………..
Answer:
Alkalies

Question 11.
Copper sulphate has five water molecules as water of ………………………..
Answer:
Crystallisation.

Question 12.
Common salt behaves as deliquescent because of the presence of ………………………..
Answer:
MgCl₂.

Multiple Choice Questions:

Question 1.
Many salts absorb water from the atmosphere, This property is called ………….
(a) Crystallisation
(b) Hydration
(c) Deliquescence
(d) Efflorescence
Answer:
(c) Deliquescence

Question 2.
Which of the following indicators is not an acid-base indicator ………….
(a) Phenolphthalein
(b) Vanilla
(c) Litmus
(d) methyl orange
Answer:
(b) Vanilla

Question 3.
Which of the following elements forms an acidic oxide ………….
(a) Mg
(b) Na
(c) P
(d) Al
Answer:
(c) P

Question 4.
The natural indicator among the following is ………….
(a) Phenolphthalein
(b) Methyl orange
(c) Methyl red
(d) Litmus
Answer:
(d) Litmus

Question 5.
An aqueous solution of sodium acetate will turn
(a) Methyl orange-yellow.
(b) Red litmus blue
(c) Phenolphthalein solution pink
(d) all of these
Answer:
(d) all of these

Question 6.
An aqueous solution of the salt is acidic. Which of the following acids and bases react to give this salt?
(a) Strong acid and strong base
(b) Strong acid & weak base
(c) Weak acid and strong base
(d) Weak acid & weak base.
Answer:
(b) Strong acid & weak base

Question 7.
An aqueous solution of which of the following substances will conduct electric current?
(a) Ethyl alcohol
(b) acetic acid
(c) Acetone
(d) Ether
Answer:
(b) acetic acid

Question 8.
A solution when added to crushed eggshells, a gas is evolved that turns lime-water milky. The solution contains.
(a) NH₄Cl
(b) NaCl
(c) KCl
(d) HCl
Answer:
(d) HCl

Question 9.
Select a pair of basic salts among the following
(a) Sodium chloride and sodium acetate
(b) Sodium acetate and sodium bicarbonate
(c) Sodium carbonate and sodium sulphate
(d) Sodium nitrate and sodium oxalate.
Answer:
(b) Sodium acetate and sodium bicarbonate

Question 10.
Which of the following substances is used an antichlor?
(a) CaOCl₂
(b) Na₂S₂O₃(c) Na₂SO₄
(d) CuSO₄Answer:
(b) Na₂S₂O₃

Question 11.
Which of the following substance has the lowest pH – value?
(a) Sugar
(b) Tomato juice
(c) Vinegar
(d) Washing soda
Answer:
(c) Vinegar

Question 12.
Which of the following indicators gives pink colour in acid solution.
(a) Methyl orange
(b) Phenolphtha lein
(c) litmus
(d) Bromothymol blue.
Answer:
(a) Methyl orange

Question 13.
A few drops of methyl orange are added to a soap solution. The colours of the solution becomes
(a) orange
(b) yellow
(c) Pink
(d) remains colourless
Answer:
(b) yellow

Question 14.
The acid formed in stomach which helps is digestion is a dilute solution of
(a) HCl
(b)H₂SO₄(c) CH₃COOH
(d) Citric acid
Answer:
(a) HCl

KSEEB Class 10 Science Acids, Bases, and Salts Additional Questions and Answers

Question 1.
What are acid-base indicators? Mention one synthetic acid-base indicator?
Answer:
Indicators are chemical substances which give different colour in acidic or basic solutions. Phenolphthalein is a synthetic indicator.

Question 2.
What are antacids?
Answer:
Antacids are mild alkalies. These are used for getting relief from acidity and indigestion and sometimes even headache. When taken orally, it reacts with HCl present in the stomach and reduces its strength by consuming some of it. Ex: Milk of magnesia is an antacid.

Question 3.
You might have seen lemon or tamarind juice being used to clean tarnished surface of copper vessels. Explain why these sour substances are effective in cleaning the vessels?
Answer:
Lemon or tamarind juice is acidic in nature and reacts with oxidised copper (compounds) to dissolve it into soluble salt and water. Thus copper vessels are cleaned.

Question 4.
What is a universal indicator? State the purpose for which this indicator is used?
Answer:
An indicator which passes through a series of colour changes over a wide range of H₃O⁺ ion concentration is called universal indicator. It is a mixture of several indicators. It is used to get approximate idea of pH of the solution.

Question 5.
Indicate with the help of diagram the variation of pH with change in concentration of H⁺(aq) and OH^–(aq) ions.
Answer:

Question 6.
Tooth enamel is one of the hardest substances in our body. How does it undergo damage due to eating chocolates and sweets? What should we do to prevent it?
Answer:
Sugar present in chocolates and sweets gets broken to acids by bacteria present in the mouth. This lowers the pH in the mouth. Tooth enamel is made up of calcium phosphate Ca₃(PO₄)₂ which gets corroded when the pH in the mouth is below 5.5. To prevent tooth enamel from decay, tooth paste is used because it is alkaline and neutralises the acid produced in the mouth and helps to prevent lowering of pH in the mouth.

Question 7.
Differentiate between
(a) acid and alkali
(b) Organic acid and mineral acid
(c) Base and Alkali
Answer:
(a) acid and alkali

Acid	Alkali
1. The compound formed by the reaction of acidic oxide with water is called acid. Ex: HCl, HNO₃,H₂SO₄	1. The hydroxide of metals which dissolve in water are known as alkalies Ex: NaOH, KOH, NH₄OH
2. These turns litmus solution red.	2. These turns litmous solution blue.

(b) Organic acid and mineral acid

Organic acid	Mineral acid
1. Organic acid contains -COOH functional group.	1. Mineral acid contains H⁺ions
2. These acids are weak Ex : Ethanoic acid, lactic acid ,eitric acid.	2. These acids are strong Ex: HCl,H₂SO_{4 ,}HNO₃

Base	Alkali
1. A base is defined as a substance which contains a hydroxyl group Ex: NaOH, KOH, Al(OH)	1. The hydroxide of metal which dissolves in water is known as alkali. Ex: NaOH, KOH, Ca(OH)₂

Question 8.
Explain the term deliquescence?
Answer:
A substance that absorbs moisture gradually from air and becomes a liquid (solution) is called deliquescent and this phenomenon is known as deliquescence.

Question 9.
Why does common salt become moist in rainy season?
Answer:
Common salt contains small amounts of magnesium chloride (MgCl₂) which is deliquescent and is responsible for sodium chloride to become moist in rainy season.

Question 10.
A house wife found that the cake prepared by her is hard and small in size. Which ingredient has she forgotten to add that would have made the cake fluffy. Give reason?
Answer:
For making cake, baking powder is taken, but the house wife must have forgotten to add baking powder (sodium bicarbonate). Because when baking powder is added as ingredient while making cake, it decomposes to produce carbon dioxide which increases the size of cake and hence, makes it soft.

Question 11.
Name the acid present in vineger?
Answer:
Ethanoic acid

Question 12.
If someone is suffering from the problem of acidity after overeating; which of the following would you suggest as a remedy?
Lemon juice, Baking soda solution or vinegar
Answer:
Baking soda solution, because it is a base and hence neutralise the excess acid present in the stomach.

Question 13.
Why does tooth decay start when the pH of mouth is lower than 5.5?
Answer:
Tooth starts decaying when the pH of our mouth is lower than 5.5. This is because below this pH value, the medium of the mouth becomes more acidic due to which tooth enamel corrodes at a faster rate.

Question 14.
A knife, which is used to cut fruit, was immediately dipped into water containing drops of blue litmus solution. The colour of the solution changes to red, what is the nature of the fruit?
Answer:
The fruit acidic as it turns blue litmus solution to red.

Question 15.
Fresh milk has a pH of 6. When it changes into curd will its pH value increase or decrease why?
Answer:
When milk changes into curd its pH value decreases. This is because during curd formation latic acid is produced which makes it acidic

Question 16.
The conditions preferred by some plants are shown in the table below.

Ph	Plant
5.0 – 6.5	Apple
4.5 – 6.0	Potato
6.0 – 8.0	Black Currant
7.0 – 8.0	Hint
6.0 – 7.0	Onipn
5.0 – 7.0	Strawberry
6.0 – 7.0	Lettuce

(a) Which plants grow well over the largest range of pH value?
Answer:
Black currant and strawberry

(b) Which plant can grow in the most acidic soil?
Answer:
Potato (4.5 – 6.0)

(d) What is the pH range for onion to grow well?
Answer:
6.0-7.0

Question 17.
Salt A commonly used in bakery products on heating gets converted into another salt ‘B’ which is used into far 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.
Answer:
Baking powder (NaHCO₃) salt. ‘A’ is commonly used in bakery products, on healing it forms sodium carbonate (Na₂CO₃) ‘B’ and CO₂ gas ‘C’ evolved. When CO₂ gas is passed through lime water it forms calcium carbonate (CaCO₃), which is slightly soluble in water making it milky
A → NaHCO₃
B → Na₂CO₃
C → CO₂ gas

Question 18.
Match the following:

1. Bleaching powder	(a) Soda-acid extinguisher
2. Baking soda	(b) Making toys
3. Washing soda	(c) Bleaching cotton and linen
4. Plaster of paris	(d) removing permanent hardness of water

Answer:

(c) Bleaching cotton and linen
(a) Soda-acid extinguisher
(d) removing permanent hardness of water
(b) Making Toys

Question 19.
Three solutions A, B, and C has pH values 5, 8 and 10 respectively. Amongest the 3 which solutions has maximum hydrogen Ion concentration. Classify the nature basic or acidic
Answer:
A has maximum (H+) concentration A is acidic. B and C are basic in nature.

Question 20.
Name a salt which does not contain water of crystallization.
Answer:
Baking soda

Question 21.
Classify the following salts as acidic, basic or neutral.
Answer:

Acidic salt- CaCl₂
Basic salt – K₂CO₃
Neutral salt – Na₂SO₄, NaCl

Question 22.
What would be the colour of litmus in a solution of sodium corbonate.
Answer:
Blue

Question 23.
How is prepared baking soda? Write the reactions. Which takes place when it is heated during cooking and name the gas evolved.
Answer:
It is prepared by using NaCl.
NaCl + H₂O + CO₂ + NH₃ → NH₄Cl + NaHCO₃
on heating
2NaHCO₃ \(\overset { \triangle }{ \rightarrow } \) Na₂CO₃ + H₂O + CO₂Carbon dioxide is evolved.

Question 24.
Write the chemical name and chemical formula of the following.
a) Bleaching powder
b) Washing soda
c) Baking soda
d) Plaster of paris
e) Common salt (brine solution)
Answer:

Chemical name	formula
a) Calcium oxychloride	CaOCl₃
b) Sodium carbonate	Na₇CO₃
c) Sodium hydrogen carbonate	NaHCO₃
d) Calcium sulphate hemihydrate	CaSO₄ 1/₂ H₂O
e) Sodium chloride	NaCl

Question 25.
Match the following:

1. When Magnesium bursts in air	a) CaCO₃ → CaO + CO₂
2. Burning of natural gas	b) CuO + H₂ → H₂O
3. Burning of natural gas	c) CH₄ + 2O₂ → CO₂+2H₂O
4. Burning of natural gas	d) 4Na + O₂→ 2Na₂O
	e) 2Mg + O₂ → 2MgO
	f) 2Cu + O₂ → 2CuO
	g) 2 AgCl \(\overset { Sunlight }{ \rightarrow } \)2Ag + cl₂

Answer:

(e) 2Mg + O₂ → 2MgO
(c) CH₄ + 2O₂ → CO₂ + H₂O
(g) 2 AgCl \(\overset { Sunlight }{ \rightarrow } \)2Ag + cl₂
(b) CuO + H₂ → H₂O