10th Science, English Medium, Syllabus of TERM-2 (2022-23)

Chapter 2 – Acids, bAses And sAlts

(One Mark Questions - 3 ; Two Marks Questions - 1 ; Three Marks Questions – 0 ; Five Marks Question - 0 : Total Marks – 5)
Question 1: You have been provided with three test tubes. One of them contains distilled water and the
other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus
paper, how will you identify the contents of each test tube?
Answer- We will put one-one drop from each test tube on red litmus paper. The solution which change the
colour of red litmus paper to blue, it is a base. Now we put one-one drop from other two test tubes on blue
litmus paper (turned blue earlier), the solution which will turn it red is an acidic solution and which will not
change colour is a neutral solution.
Question 2: Why should curd and sour substances not be kept in brass and copper vessels?
Answer- Curd and other sour substances contain acids. Therefore, when they are kept in brass and copper
vessels, the metal reacts with the acid to liberate hydrogen gas and harmful products, thereby spoiling the food.
Question 3: Which gas is usually liberated when an acid reacts with a metal? Illustrate with an example.
How will you test for the presence of this gas?
Answer- Hydrogen gas is usually liberated when an acid reacts with a metal. Take few pieces of zinc granules
and add 5 ml of dilute H2SO4 . In this reaction hydrogen gas will be produced. We can test the evolved
hydrogen gas by its burning with a pop sound when a burning candle is brought near.
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- CaCO3 + 2HCl CaCl2 + CO2 + H2O
Calcium carbonate hydrochloric acid calcium chloride carbon dioxide water
Question 5: Why do HCl, HNO3 , etc., show acidic characters in aqueous solutions while solutions of
compounds like alcohol and glucose do not show acidic character?
Answer- Because HCl, HNO3 etc dissociate in water to form hydrogen ions (H+), but glucose and alcohol do
not dissociate.
Question 6: Why does an aqueous solution of an acid conduct electricity?
Answer- Acids dissociate in aqueous solutions to form ions. These ions are responsible for conduction of
electricity.
Question 7: Why does dry HCl gas not change the colour of the dry litmus paper?
Answer- Because dry HCl does not give hydrogen ions (H+) without water. Hence it does not act as acid.
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- Since the process of dissolving an acid in water is exothermic, it is always recommended that acid
should be added to water. If it is done the other way, then it is possible that because of the large amount of heat
generated, the mixture splashes out and causes burns.
Question 9: How is the concentration of hydronium ions (H3O+) affected when a solution of an acid is
diluted?
Answer- When an acid is diluted, the concentration of hydronium 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?

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Answer- The concentration of hydroxide ions (OH ) would increase when excess base is dissolved in a solution
of sodium hydroxide.
Question 11: You have two solutions, A and B. The pH of solution A is 6 and pH of solution B is 8. Which
solution has more hydrogen ion concentration? Which of this is acidic and which one is basic?
Answer- A pH value of less than 7 indicates an acidic solution, while greater than 7 indicates a basic solution.
Therefore, the solution with pH = 6 is acidic and has more hydrogen ion concentration than the solution of pH =
8 which is basic.
Question 12: What effect does the concentration of hydrogen ions (H+) have on the nature of the solution?
Answer- With an increase in H+ ion concentration, the solution becomes more acidic, while a decrease of H+
ion causes an increase in the basicity of the solution.
Question 13: Do basic solutions also have H+ (aq) ions? If yes, then why are these basic?
Answer- Yes, basic solution also has H+ ions. However, their concentration is less as compared to the
concentration of OH- ions that makes the solution basic.
Question 14: Under what soil condition do you think a farmer would treat the soil of his fields with quick
lime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate) ?
Answer- If the soil is acidic and improper for cultivation, then to increase the basicity of soil, the farmer would
treat the soil with quick lime or slaked lime or chalk.
Question 15: What is the common name of the compound CaOCl2 ?
Answer- The common name of the compound CaOCl2 is bleaching powder.
Question 16: Name the substance which on treatment with chlorine yields bleaching powder?
Answer- Calcium hydroxide [Ca (OH)2].
Question 17: Name the sodium compound which is used for softening hard water.
Answer- Washing soda (Na2CO3 .10H2O) is used for softening hard water.
Question 18:- What will happen if a solution of sodium hydrogencarbonate is heated? Give the equation
of the reaction involved.
Answer- When a solution of sodium hydrocarbonate (sodium hydrogencarbonate-NaHCO3) is heated, sodium
carbonate and water are formed with the evolution of carbon dioxide gas.

Question 19: Write an equation to show the reaction between Plaster of Paris and water.
Answer- POP reacts with water to form gypsum.

EXERCISE
Question 1: A solution turns red litmus blue, its pH is likely to be
(a) 1 (b) 4 (c) 5 (d) 10 ✓
Question 2: A solution reacts with crushed egg-shells to give a gas that turns lime-water milky. The
solution contains
(a) NaCl (b) HCl ✓ (c) LiCl (d) KCl

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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 of HCl solution (the same
solution as before) required to neutralise it will be
(a) 4 mL (b) 8mL (c) 12 mL (d) 16 mL ✓
Question 4: Which one of the following types of medicines is used for treating indigestion?
(a) Antibiotic (b) Analgesic (c) Antacid ✓ (d) Antiseptic
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) Sulphuric acid + Zinc → Zinc sulphate + Hydrogen
H2SO4 + Zn → ZnSO4 + H2
(b) Hydrochloric acid + Magnesium → Magnesium chloride + Hydrogen
2HCl + Mg → MgCl2 + H2
(c) Sulphuric acid + Aluminium → Aluminium sulphate + Hydrogen
3H2SO4 + 2Al → Al2(SO4)3 + 3H2
(d) Hydrochloric acid + Iron → Iron (II) chloride + Hydrogen
HCl + Fe → FeCl2 + H2
Question 6: Compounds such as alcohols and glucose also contain hydrogen but are not categorized as
acids. Describe an activity to prove it.
Answer- Because alcohols and glucose do not dissociate into hydrogen ions, hence these cannot be categorized
as acids.
Activity- Make a circuit as shown in figure. When we pour HCl in beaker then bulb glows, but when we pour
alcohol or glucose solution in beaker then bulb do not glow. This is because of absence of ions in alcohol and
glucose solutions.

Question 7: Why does distilled water not conduct electricity, whereas rain water does?
Answer- Distilled water is a pure form of water and is devoid of any ionic species. Therefore, it does not
conduct electricity. Rain water, being an impure form of water, contains many ionic species such as acids and
therefore it conducts electricity.
Question 8: Why do acids not show acidic behavior in the absence of water?

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Answer- Acids do not show acidic behavior in the absence of water, because acids dissociate into hydrogen
ions only in the presence of water. It is the hydrogen ions that are responsible for the 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?
(e) weakly alkaline?
Arrange the pH in increasing order of hydrogen-ion concentration.
Answer- (a) Neutral → Solution D with pH 7
(b) Strongly alkaline → Solution C with pH 11
(c) Strongly acidic → Solution B with pH 1
(d) Weakly acidic → Solution A with pH 4
(e) Weakly alkaline → Solution E with pH 9.
The pH can be arranged in the increasing order of the concentration of hydrogen ions as: 11 < 9 < 7 < 4 < 1
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 acid (CH3COOH) is added to test tube B. In which test tube
will the fizzing occur more vigorously and why?
Answer- The fizzing will occur strongly in test tube A, in which hydrochloric acid (HCl) is added. This is
because HCl is a stronger acid than CH3COOH and therefore produces hydrogen gas at a faster speed due to
which fizzing occurs.
Question 11: Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd?
Explain your answer.
Answer- The pH of milk is 6. As it changes to curd, the pH will reduce because curd is acidic in nature. The
acids present in it decrease the pH.
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 milkman shifts the pH of the fresh milk from 6 to slightly alkaline because in alkaline
condition, milk does not set as curd easily.
(b) Since this milk is slightly basic than usual milk, acids produced to set the curd are neutralized by the base.
Therefore, it takes a longer time for the curd to set.
Question 13: Plaster of Paris should be stored in a moisture-proof container. Explain why?
Answer- Plaster of Paris (POP) should be stored in a moisture-proof container because Plaster of Paris, a
powdery mass, absorbs water (moisture) to form a hard solid known as gypsum.
Question 14: What is a neutralization reaction? Give two examples.
Answer- When an acid mixed with a base then they react with each other to form the salt and water with the
release of energy and cancel each other's effect. This process is neutralization process.
Acid + Base → Salt + Water + Heat
Example: (1) NaOH + HCl → NaCl + H2O + Heat

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(2) During indigestion (caused due to the production of excess of hydrochloric acid in the stomach),
we take an antacid (generally milk of magnesia, which is basic in nature). The antacid neutralizes the excess of
acids and thus gives relief from indigestion.
Question 15: Give two important uses of washing soda and baking soda.
Answer- (1) Important uses of Washing soda: (a) It is used in glass, soap, and paper industries.
(b) It is used to remove permanent hardness of water.
(2) Important uses of Baking soda: (a) It is used as baking powder. (Baking powder is a mixture of baking
soda and a mild acid known as tartaric acid. When it is heated or mixed in water, it releases CO2 that makes
bread or cake fluffy.)
(b) It is used in soda-acid fire extinguishers.
Some Important things to remember

Sr. Common Name Chemical Name

Chemical Formula
No. Of Compound Of Compound
1 NaCl Common Sat Sodium Chloride
2 NaOH Caustic Soda Sodium Hydroxide
3 CaO Quick Lime Calcium Oxide
4 Ca(OH)2 Slaked Lime Calcium Hydroxide
5 CaCO3 Lime Stone Calcium Carbonate
6 CH3COOH Vinegar or Acetic Acid Ethanoic Acid
7 CaOCl2 Bleaching Powder Calcium hypo Chloride
Sodium Bicarbonate or
8 NaHCO3 Baking Soda
Sodium Hydrogen Carbonate
9 Na2CO3-10H2O Washing Soda Sodium Carbonate
10 CuSO4-5H2O Blue Vitriol Copper Sulphate
11 CaSO4- H2O Plaster of Paris (POP) Calcium Sulphate
12 CaSO4-2 H2O Gypsum Calcium Sulphate

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 10th Science, English Medium, Syllabus of TERM-2 (2022-23)

Chapter 3 – Metals and non-metals

(One Mark Questions - 2 ; Two Marks Questions - 0 ; Three Marks Questions – 0 ; Five Marks Question - 1 : Total Marks – 5)
Question 1: Give an example of a metal which:
(i) Is a liquid at room temperature?
Answer- Mercury
(ii) Can be easily cut with a knife?
Answer- Sodium and potassium.
(iii) Is the best conductor of heat?
Answer- Silver.
(iv) Is a poor conductor of heat?
Answer- Mercury
Question 2: Explain the meanings of malleable and ductile.
Answer- (i) Metals can be beaten to form sheets, they are said to be malleable.
(ii) Metals can be drawn into thin wires, they are said to be ductile.
Question 3: Why is sodium kept immersed in kerosene oil?
Answer- Sodium and potassium are very reactive metals, if kept open these can react with oxygen and water
and may catch fire. Hence Sodium and potassium are kept immersed in kerosene to prevent their reaction with
oxygen and moisture.
Question 4: Write equations for the reactions of:
(i) Iron with steam.
(ii) Calcium and potassium with water.
Answer- (i) Iron reacts with steam to form a magnetic oxide of Fe with the liberation of Hydrogen gas.
3Fe(s) + 4H2O(g) → Fe3O4 (s) + 4H2 (g)
(ii) Calcium reacts with water to form calcium hydroxide and hydrogen gas.
Ca(s) + 2H2O(l) → Ca(OH)2 (aq) + H2 (g)
Potassium reacts with cold water violently immediately with evolution of hydrogen gas, Which catches fire.
2K(s) + 2H2O(l) → 2KOH(aq) + 2H2 (g)
Question 5: Samples of four metals A, B, C and D were taken and added to the following solution one by
one. The results obtained have been tabulated as follows:

Copper(II)
Metal Iron(II) sulphate Zinc sulphate Silver Nitrate
sulphate

A No reaction Displacement - -

Because Displacement - - -

C No reaction No reaction No reaction Displacement

D No reaction No reaction No reaction No reaction

Use the Table above to answer the following questions about metals A, B, C and D.
(i) Which is the most reactive metal?
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Answer- Metal B.
(ii) What would you observe if B is added to a solution of Copper (II) sulphate?
Answer- If B is added to a solution of copper (II) sulphate, then it would displace copper and blue colour of
copper sulphate will disappear.
(iii) Arrange the metals A, B, C and D in the order of decreasing reactivity.
Answer- B > A > C > D
Question 6: Which gas is produced when dilute hydrochloric acid is added to a reactive metal? Write the
chemical reaction when iron reacts with dilute H2SO4
Answer- Hydrogen gas is liberated when dilute HCl is added to a reactive metal.
Fe(s) + H2SO4 (aq) → FeSO4 (aq) + H2 (g)
Question 7: What would you observe when zinc is added to a solution of iron (II) sulphate? Write the
chemical reaction that takes place.
Answer- Zinc is more reactive (more electro positive) than iron. Therefore Zinc displaces Iron from its salt
solution. The colour of ferrous sulphate is light green, which turns colourless.
FeSO4 + Zn → ZnSO4 + Fe(s)
Light green Zinc sulphate (Colourless)
Question 8: (i) Write the electron-dot structures for sodium, oxygen and magnesium.
Answer- Sodium Oxygen Magnesium

(ii) Show the formation of Na2 O and MgO by the transfer of electrons.
Answer-

(iii) What are the ions present in these compounds?

Answer- The ions present in Magnesium oxide compound (MgO) are magnesium ions Mg2+ (cation) and oxide
ions (O2-) (anion).The ions present in Sodium oxide compound(Na2 O) are sodium(Na+) cation and oxide ions
(O2-) (anion).
Question 9: Why do ionic compounds have high melting points?
Answer- Ionic compounds have strong electrostatic forces of attraction between the ions. Therefore, it requires
a lot of energy to overcome these forces. That is why ionic compounds have high melting points
Question 10: Define the following terms.
(i) Mineral (ii) Ore (iii) Gangue.
Answer- (i) Mineral: Most of the elements occur in nature as in combined state as minerals. The chemical
composition of minerals is fixed.
(ii) Ore: Minerals from which metals can be extracted profitably are known as ores.
(iii) Gangue: The impurities (sand, silt, soil, gravel, etc.) present in the ore are called gangue.
Question 11: Name two metals which are found in nature in the free state.
Answer- Gold, silver, and platinum.

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Question 12: What chemical process is used for obtaining a metal from its oxide?
Answer- The chemical process used for obtaining a metal from its oxide is reduction. In this process, metal
oxides are reduced by using suitable reducing agents such as carbon or by highly reactive metals to displace the
metals from their oxides.
Question 13: Metallic oxides of zinc, magnesium and copper were heated with the following metals.
Metal Zinc Magnesium Copper
Zinc Oxide
Magnesium
Oxide
Copper Oxide
In which cases will you find displacement reactions taking place?
Answer- Order of reactivity of these metals is as: Mg > Zn > Cu
Metal Zinc Magnesium Copper
Zinc Oxide - Displacement -
Magnesium Oxide - - -
Copper Oxide Displacement Displacement -

Question 14: Which metals do not corrode easily?

Answer- Gold and platinum are the metals which do not corrode easily.
Question 15: What are alloys?
Answer- An alloy is a homogeneous mixture of two or more metals, or a metal and a non- metal.
EXERCISE QUESTION-ANSWERS
Question 1: Which of the following pairs will give displacement reactions?
(a) NaCl solution and copper metal (b) MgCl2 solution and aluminium metal
(c) FeSO4 solution and silver metal (d) AgNO3 solution and copper metal ✓
Question 2: Which of the following methods is suitable for preventing an iron frying pan from rusting?
(a) Applying grease (b) Applying paint
(c) Applying a coating of zinc ✓ (d) All of the above
Question 3: An element reacts with oxygen to give a compound with a high melting point. This compound
is also soluble in water. The element is likely to be
(a) Calcium ✓ (b) Carbon (c) Silicon (d) Iron
Question 4: Food cans are coated with tin and not with zinc because
(a) Zinc is costlier than tin. (b) Zinc has a higher melting point than tin.
(c) Zinc is more reactive than tin. ✓ (d) Zinc is less reactive than tin.
Question 5: You are given a hammer, a battery, a bulb, wires and a switch.
(a) How could you use them to distinguish between samples of metals and non- metals?
(b) Assess the usefulness of these tests in distinguishing between metals and non- metals.

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Answer- (a) With the hammer, we can beat the sample and if it can be beaten into thin sheets (that is, it is
malleable), then it is a metal otherwise a non-metal. Similarly, we can use the battery, bulb, wires, and a switch
to set up a circuit with the sample. If the sample conducts electricity, then it is a metal otherwise a non-metal.
(b) These experiments can be helpful to demonstrate the malleability and electric conductivity of the
metals and non-metals.
Question 6: What are amphoteric oxides? Give two examples of amphoteric oxides
Answer- Oxides that react with both acids and bases to form salt and water are known as amphoteric oxides.
Amphoteric oxides show properties of both acids and bases. Examples: PbO and Al2O3 .
Question 7: Name two metals which will displace hydrogen from dilute acids, and two metals which will
not.
Answer- Zinc (Zn) and Magnesium (Mg) are the two metals which will displace Hydrogen from dilute acids as
they are very reactive metals. Gold (Au) and Silver (Ag) are the metals which will not replace Hydrogen from
dilute acids as these metals are less reactive.
Question 8: In the electrolytic refining of a metal M, what would you take as the anode, the cathode and
the electrolyte?
Answer- In the process of electrolytic refining of metal called ‘M’, An impure and thick block of metal M is
considered as anode, Thin strip or wire of pure metal M is taken as cathode. A suitable salt solution of metal M
is considered as the electrolyte.
Question 9: Pratyush took sulphur powder on a spatula and heated it. He collected the gas evolved by
inverting a test tube over it, as shown in figure below.

(a) What will be the action of gas on:

(i) dry litmus paper?
(ii) moist litmus paper?
(b) Write a balanced chemical equation for the reaction taking place.
Answer- (a) When sulphur powder is burnt in the air sulphur dioxide is formed.
(i) Sulphur dioxide does not have any effect on dry litmus paper.
(ii) Sulphur dioxide turn the moist litmus paper from blue to red because contact of SO2 with water turns
to sulfurous acid.
(b) S(s) + O2 (g) → SO2 (g)
and SO2 (g) + H2O → H2SO3
Question 10: State two ways to prevent the rusting of iron.
Answer- Iron can be prevented from rusting by:
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(i) Painting, (ii) Greasing, (iii) Galvanization (Coating with zinc),(iv) By connecting with another active metal.
Question 11: What types of oxides are formed when non-metals combine with oxygen?
Answer- When non-metals combine with oxygen it forms either acidic or neutral oxides. Ex: SO2 is an acidic
oxide; CO is a neutral oxide.
Question 12: Give reasons:
(a) Platinum, gold and silver are used to make jewellery.
Answer- Platinum, gold and silver are used to make jewellery as these metals are very less reactive hence
they are not affected by air, water or most chemicals. These metals have a lot of lustre and they are malleable
and ductile in nature.
(b) Sodium, potassium and lithium are stored under oil.
Answer- Sodium and potassium are very reactive metals, if kept open these will react with oxygen and water to
catch fire. Hence Sodium and potassium are kept immersed in kerosene to prevent their reaction with oxygen
and moisture.
(c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.
Answer- This is because aluminium reacts with oxygen present in air to form a thin layer of aluminium oxide.
This oxide layer is very stable and prevents further reaction of aluminium with oxygen. Also, it is light in
weight and a good conductor of heat. Hence, it is used to make cooking utensils.
(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction.
Answer- Because metals can be easily extracted from their oxides rather than from their carbonates and
sulphides.
Question 13: You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice.
Explain why these sour substances are effective in cleaning the vessels.
Answer- Tarnished copper vessels being cleaned with lemon or tamarind because these sour substances
contains acids which dissolve the layer of copper oxides and basic copper carbonate present on the surface of
tarnished copper vessels. This makes them shining red-brown again. Hence they are very effective in cleaning
tarnished copper vessels.
Question 14: Differentiate between metal and non-metal on the basis of their chemical properties.
Answer-
Metals Non-metals
On the basis of Chemical properties
(i) When metals are heated with oxygen, they (i) When non-Metals are heated with oxygen, they form
form ionic oxides which are basic in nature. covalent oxides which are acidic in nature.

(ii) They are electro positive, lose (ii) They are electro negative, gain electrons and
electrons readily and become a positive ion. become negative ions.

(iii) Metals are reducing agents. (iii) Non-metals are oxidizing agents.
On the basis of Physical properties
(iv) Metals are lustrous. (iv) Non-metals are non-lustrous; graphite is the
exception.

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(v) Metals are the good conductors of electricity (v) Non-metals are non-conductors of electricity and
and heat. heat; graphite is the exception

(vi) All metals are solids except mercury. (vi) Non-metals are in solid, liquid and gaseous states.

Question 15: A man went door to door posing as a goldsmith. He promised to bring back the glitter of old
and dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him which he dipped in a
particular solution. The bangles sparkled like new but their weight was reduced drastically. The lady was
upset but after a futile argument the man beat a hasty retreat. Can you play the detective to find out the
nature of the solution he had used?
Answer- Goldsmith used the solution called Aqua regia. It is the mixture of concentrated Hydrochloric acid and
concentrated nitric acid in the ratio of 3:1. Aqua regia is capable of dissolving noble metals like gold and
platinum. When upper-layer of dull gold ornament is dissolved they lose their weight.
Question 16: Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).
Answer- Because copper does not reacts with either water or steam whereas iron reacts with steams to corrode
the tank.

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