The following questions are prepared for the  HSLC Examination conducted by SEBA, Assam. It covers the all-important questions part of Science Core paper. It is very necessary for an HSLC candidate as most of the probable questions are included here. While composing the questions the pattern of HSLC Final questions is kept in mind so that it will be a perfect guide for a learner. We are providing the important and the most probable questions in an easy and suitable manner so that the candidates get more scope for practice and revision. Our Faculty members are trying at best to enrich the website with the most important questions with appropriate answers.


General Science


Chapter 2:- Acids, Bases, and Salts


ACIDS, Bases and salts


Chapter: 2

HSLC Exam. Questions

A.  Very Short Type Questions                                                                        Mark : 1

  1. A solution reacts with crushed egg-shells to

give a gas that turns lime water milky. The solution contains —–                     [HSLC 15]



(c) LiCl.


Ans– (b) HCl

Reaction:- HCl (aq) + CaCO3 (eggshell)   ———->   CaCl2  + CO2   + H2O

  1. A solution turns red litmus blue. The pH of the solution is ———                  [HSLC 16]

(a) 1


(c) 5

(d) 10

Ans:- (d) 10

Short type Questions                                                                                                    Mark2/3

  1. What is pH?

You are given 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 these solutions is acidic and which one is basic?                                                                                                       Ans:- A pH scale is a scale for measuring Hydrogen ion (H+) concentration in a solution. i.e. pH of a solution is a number which indicates the acidic or basic nature of the solution. It ranges from 0 to 14.

Solution A has more hydrogen ion concentration.
Solution A is acidic and solution B is basic.

2. What is Plaster of Paris? How is it prepared? Give one important use.         [HSLC 15]

Ans:-On heating gypsum at 373K, it loses water molecules and becomes calcium sulphate hemihydrate (CaSO_{4}.\frac{1}{2}H_{2}O). This is called Plaster of Paris.

Use– doctors use this as Plaster for supporting fractured bones in the right position.

3. Name the Sodium compound which is used for softening hard water. HSLC 16

Ans:- Washing soda (Sodium carbonate) Na_{2}CO_{3}

Choose the correct answer from the following alternatives:-

(i) The acid found in curd—

(a) Oxalic acid

(b) tartaric acid

(c) lactic acid.

Ans:- (c) lactic acid.

(ii) The taste of soap solution is a bitter test because a soap solution is a—

(a) alkaline

(b) acidic

(c) both (a) and (b)

Ans:- (a) alkaline

(iii) When zinc is combined with an aqueous solution of sodium hydroxide production of–


(b) N2 gas

(c) H2 gas

Ans:- (c) H2 gas

(iv) When alkali reacts with an acid, they will produce–

(a) salt and water

(b) salt and hydrogen gas

(c) water and hydrogen gas

Ans:- (a) salt and water

(v) In aqueous solution acid releases-

(a) H+ ion

(b) OH ion

(c) both (a) and (b)

Ans:- (a) H+ ion

(vi) Hydrochloric acid is a-

a) oxyacid

(b) hydracid

(c) both (a) and (b)

Ans:- (b) hydracid
(vii) when blue litmus is added to liquid HCI solution, what will be the colour–
(a) colourless
(b)no change, blue colour
(c) red colour
(d) green colour

Ans:- (c) red colour

(vii) The taste of liquid NaOH is-

(a) soar

(b) bitter


(d) salted

Ans:- (b) bitter

(ix) Which of the following gas will be produced when liquid sulphuric acid is added to a piece of sodium hydroxide-





Ans:- (a)H2

(x) Methyl orange is-

(a) Red in acidic medium, colorless in basic medium

(b) Yellow in acidic medium, red in basic medium.

(c) Red in acidic medium, yellow in basic medium

(d) Colorless in acidic medium, red in
basic medium.

Ans:- (c) Red in acidic medium, yellow in basic medium

(xi) Lemon juice and coffee are–

(a) Both basic

b) Lemon juice is acidic coffee is basic.

(c) Both acidic

(d) Lemon juice is basic coffee is acidic.

Ans:- (c) Both acidic

xii) A solution turns red litmus blue, its P^{H}is likely to be–

(a) 10




Ans:- (a) 10
(xiii) Which one of the following type of medicine is used for treating indigestion–

(a) Antacid

(b) Antiseptic

(c) antibiotic

(d) Analgesic

Ans:- (a) Antacid

(xiv) Which among the following is not a base—

(a) C_{2}H_{5}OH

(b) KOH

(c) NH_{4}OH

(d) NaOH

Ans:- (a) C_{2}H_{5}OH

(xv) Which of the following is used for dissolution of gold?

(a) Aqua regia

(b) Sulphuric acid

(c) Nitric acid

(d) Hydrochloric acid

Ans:- (a) Aqua regia

(xvi) Which one of the following can be used as an acid-base indicator by a visually impaired students-
(a) Turmeric
(b) Litmus
(c) Vanilla essence
(d) Petunia leaves
Ans:- (c) Vanilla essence

(xvii) An aqueous solution turns red litmus solution blue. Excess addition of which of the following solution would reverse the change?
(a) Hydrochloric acid
(b) Ammoniun hydroxide solution.
(c) Lime
(d) Baking powder
Ans:- (a) Hydrochloric acid

(xviii) Sodium Carbonate is a basic salt because it is a salt of-
(a) strong acid and weak base
(b) weak acid and weak base
(c) strong acid and strong base
(d) weak acid and strong base
Ans:- (a) strong acid and weak base

(xix) Calcium phosphate is present in tooth enamel. Its nature is-
(a) basic
(b) acidic
(c) neutral
(d) amphoteric
Ans:- (a) basic

(xx) Which of the following gives the correct increasing order of acid strength?
(a) Hydrochloric acid water Acetic acid
(b) Acetic acid water Hydrochloric acid
(c) Water hydrochloric acid Acetic acid
(d) Water Acetic acid Hydrochloric acid
Ans:- (d) Water Acetic acid Hydrochloric acid

(xxi) One of the constituents of baking powder is sodium hydrogen carbonate, the other constituents are-
(a) sulphuric acid
(b) acetic acid
(c) tartaric acid
(d) hydrochloric acid
Ans:-(c) tartaric acid

(xxii) To protect tooth decay we are advised to brush our teeth regularly. The nature of toothpaste commonly used-
(a) Neutral
(b) acidic
(c) corrosive
(d) basic
Ans:-(d) basic

(xxiii) Which one of the following salts does not contain water of crystallisation?
(a) Blue vitrol
(b) Baking soda
(c) Washing soda
(d) Gypsum
Ans:- (b) Baking soda

(xxiv) Brine is an
(a) an aqueous solution of sodium bicarbonate.
(b) an aqueous solution of sodium chloride.
(c) an aqueous solution of sodium carbonate.
(d) an aqueous solution of sodium hydroxide.
Ans:- (b) aqueous solution of sodium chloride.

(xxv) Borax is manufactured from-
(a) washing soda
(b) baking powder
(c) bleaching powder
(d) baking soda
Ans:-(a) washing soda

(xxvi) Alkalis are-
(a) acids, which are soluble in water.
(b) bases, which are soluble in water.
(c) acids, which are insoluble in water.
(d) bases, which are insoluble in water.
Ans:- (b) bases, which are soluble in water.

(xxvii) Lime water reacts with chlorine to give-
(a) baking soda
(b) washing soda
(c) bleaching powder
(d) baking powder
Ans:-(c) bleaching powder

(xxviii) Sodium hydroxide is used-
(a) weak acid.
(b) weak base.
(c) strong acid.
(d) strong base.
Ans:- (d) strong base.

(xxix) Sodium hydroxide is used–
(a) as an antacid
(b) in the manufacture of soap
(c) in alkaline batteries
(d) as a cleansing agent
Ans:- (b) in the manufacture of soap

(xxx) Salt used in food is–
(a) sodium chloride
(b) sodium hydroxide
(c) calcium chloride
(dy sodium acetate
Ans:-(a) sodium chloride

(xxxi) A sample of soil is mixed with water and allowed to settle. The clear spearmint solution turns the PH paper yellowish- orange. Which of the following would change the colour of this PH paper to greenwish blue?
(a) Vinegar
(b) Lemon juice
(c) Common salt
(d) an antacid
Ans:- (d) an antacid


2. Fill in the blanks
(i) Due to the presence of _________ acid, the taste of citrus is soar.

Ans:- Citric.

(i) _________ acid is found in an orange.

Ans:- Citric.

(ii) ________ acid is found in gastric juice.

Ans:- HCl.

(iv) All the alkalies are base but all the bases are not

Ans:- Alkali

(v) ________ is dissolved in soda water that is why acidic in nature.

Ans:- CO2.

(vi) Acids and alkali are ________.

Ans:- Salt.

(vii) when nitric acid reacts with metal, production of nitrate of metal, _________ oxides, nitrogen gas ________.


(viii) When manganese reacts with dilute nitric acid production of _______ gas.

Ans:- H2

(ix) When an acid reacts with a base, production of _______ and _______.

Ans:- Salt and water.

(x) The base releases ________ion in aqueous solution.

Ans:- OH.

(xi) _______ change the red litmus into blue

Ans:- Base.

(xii) When base reacts with oxides of metal, production of _______ and _______.

Ans:- Salt and water.

(xiii) Hydracids are _______ compound.

Ans:- Benary.

(xiv) Perchloric acid ______ of halogen.

Ans:- Oxyacid.

(xv) Phenolphthalein is a _______ indicator and the colour of it is pink in ________ solution.

Ans:- Synthetic, basic.

(xvi) Pof the basic solution is always ______ than 7.

Ans:- More.

(xvii) ________ is used in soda-acid fire extinguishers.

Ans:- Baking soda.

(xviii) _______ is used for disinfecting drinking water to make it free of germs.
the production of baking soda.

Ans:- Baking powder.

(xix) ———- is one of the raw materials for the production of baking soda.

Ans:- NaCl (brine).

(xx) During indigestion, the stomach produces —– too much. and this cause pain and irritation, and this cause pain and irritation.


13. Determine true or false.
(i) When acid reacts with metals, production of hydrogen gas and salts of that metal.
(ii) When magnesium reacts with dilute nitric acid, production of carbon dioxide gas.
(iii) When acid reacts with bicarbonate then production of carbon dioxide
(iv) Acids reacts with oxides of metal to produce salt and water.
(v) Acids and bases are non-electrolytes
(vi) The anion of arsenic acid is arsenite.
(vii) Litmus is an oxidation-reduction indicator.
(vii) The red litmus is on changed into blue colour in acidic medium.
(ix) Phenolphthalein is a natural indicator.
(x) Both bases and alkalis are soluble in water.
(xi) To get optimum Ph of acidic soil, it is treated with dilute carbonic acid.
(xii) Copper sulphate crystals are always wet due to the presence of water of crystallisation in them.
(xiii) Plaster of Paris should be stored in a moisture-proof container.
(xiv) Bleaching powder reacts with dilute acids to produce Chlorine.

4. Name the acid which is found in vinegar.
Ans:- acetic acid.

5. What do you mean by acid?
Ans:-Acid are those chemical substances which have a sour taste.Acid change the colour of blue litmus to red. Actually, an acid is a substance which dissociates (or ionises) on dissolving in water to produce hydrogen ions (H^{+} ions).

6.what is called concentrated acid? Give example.
Ans:- A concentrated acid is one which contains the minimum possible amount of water in it.[ A concentration of acid is decreased by adding more water to Cl.]Eg:-

ConC.HNO_{3}, ConC.H_{2}SO_{4} etc.

7. What is called dilute acid? Give example.
Ans:- A dilute acid in one which contains much more water in it. Dilute acid is obtained by mixing the concentrated acid with water.Eg:

dil.H_{2}SO_{4} ,dil.HCl. etc.

8. What is called base? Give example.
Ans:- Base are those chemical substances which have a bitter taste. A common property of all bases (or alkalis ) is that they all produce hydroxide ions (OH^{-} ions).
Eg: NaOH, KOH, Ca(OH)_{2} etc.

9. What is called alkali? Give an example
Ans:- A base which is soluble in water is called an alkali.
Eg: Common alkalis are  Ca(OH)_{2}NaOH, KOH, NH_{4}OH \;and \; Mg(OH)_{2}.

10. Name one each of concentrated base and dilute base.
Ans:-Conc NaOH and dil. KOH

11. What changed will be seen when the blue litmus solution is added to the citrus juice?
Ans:- When blue litmus solution is added to citric acid, it turns into Red because of acidic character.

12. How you will prove that the orange juice is either acidic or basic with the help of litmus?
Ans:- Orange Juice is acidic because it turns blue litmus red.

13. Why is lime water basic in nature?
Ans:- Lime water reacts with hydroxide ion of the water molecule and forms Ca(OH)_{2}, which is basic in nature.

14. Why are the fruit juice and curd not kept in the pot of bell metal?
Ans:-Fruit Juice and curd are acidic in nature they react with them (metal) and form poisonous which may prove harmful for human body. That’s why they are not kept in the pot of bell metal.

15. What is called oxyacid? Give example.
Ans:- An oxyacid is an acid that contains an oxygen atom bonded to a hydrogen atom and at least one other element.

Eg: H_{2}SO_{4} , HNO_{3} etc.

16. Name the plants from where the litmus pigment can be obtained?
Ans:-Litmas is a natural indicator which is extracted from a type of plant called lichen belonging to the division Thallophyta.

17. What is called indicator? Give an example
Ans: An indicator is a dye that changes colour when it is put into an acid or a base.

Eg: The most common indicators are litmus, methyl orange and phenolphthalein.

18. What do you mean by a factory indicator?
Ans:-Those substances whose smell (or odour) changes in acidic or basic solutions are called olfactory indicators. Onion and Vanilla extract are olfactory indicators.

19. Write the reaction between metal oxide dilute HCl?
Ans:-Metal oxide + acid ⇒  salt + water

CuO + 2HCl\rightarrow CuCl_{2}+ H_{2}O

20. Why are metallic oxide called basic oxides?
Ans:-because it reacts with an acid to form salt and water.

21. What is a universal indicator?
Ans:-Universal indicator is a mixture of many different indicators (or dyes) which gives different colours at different PH values of the entire PH scale.

22. What is PH?
Ans:-The strength of an acid or base is measured on a scale of numbers called PH scale.The PH scale values from O to 14.

23. What are acidic salts? Give examples?
Ans:-Salts which make medium acidic when dissolved in an aqueous medium are known as acidic salts.
eg: ammonium chloride, sodium bicarbonate etc.
[ A salt formed between a strong acid and weak base is an acid salt. for example NH_{4}Cl.]

24. What are basic salts? Give examples
Ans:- A salt formed between a weak acid and a strong base is a basic salt.


25: Name the products which are formed from the chloro-alkali process?
Ans:-NaOH (aq)\;,Cl_{2}(g)\; and \;H_{2}(g)

26. Write the chemical formulae of the following salts washing soda, Baking soda bleaching powder.
Ans:-washing soda:-Na_{2}CO_{3}.10H_{2}O

Baking soda:-NaHCO_{3}

bleaching powder:-CaOCl_{2}

27. What type of PH should the soil have for health growth of plant?
Ans:-The PH of soil is close to 7.

28. Which acid is injected into our body by a besetting that causes pain?
Ans:- methanoic acid or formic acid.

29. What do you mean by hygroscopic nature of common salt?
Ans:- The phenomenon by which common salt absorbs moisture from the atmosphere due to the presence of components like MgCl2 is called hygroscopy.
Hygroscopic nature means it tends to draw water (or absorb water ) when exposed to air. But not all salts are hygroscopic in nature.

30. What is the common name of sodium hydrogen carbonate?
Ans:- baking soda.

31. Name one metal carbonate which is soluble in water and one which is insoluble in water?
Ans:-NaHCO_{3} soluble in water but CaCO_{3} does not dissolve in water.

32. Where is hydrogen used as a fuel?
Ans:- Hydrogen fuel is used in space rocket fuel, electrochemical cells,as well as automobiles and other transportation vehicles.

33. Out of tap water, sea water and pure water, which is the best conductor of electricity?
Ans:- sea water is the best conductor of electricity as it contains a large number of dissolved salts in it.

34. Why is sulphuric acid called “King of Chemicals”?
Ans:- The sulphuric acid called “King of Chemicals” because it is widely used in the manufacture of many other chemicals and products.

B. Short Type Questions Marks: 2/3 

1. What is an acid-base indicator? Give two examples of synthetic acid-base indicators?
Ans:- An acid-base indicator indicates that whether the given substance is an acid or a base by a change in its colour.
Two examples of synthetic acid-base indicators are-
phenolphthalein and methyl orange.

2. What is the difference between a strong acid and weak acid? Give two examples from each.
Ans:- Strong acid:- an acid which is completely ionised in water and thus produce a large amount of H^{+} ion is called a strong acid. e.g. HCl, H_{2}SO_{4} etc.
all mineral acids are strong acid except carbonic acid. Strong acids are dangerous to drink.

Weak acid:- An acid which is partially ionised in water and thus produces a small amount of H+ ion is called weak acid. e.g.CH_{3}COOH(ACETIC ACID), H_{2}CO_{3} (carbonic acid) etc.
The organic acids are weak acid and quite safe to drink.

3. What is the difference between a strong base and a weak base? Give two examples from each.
Ans:- Strong Base:- A base which completely ionises in water and thus produces a large number of hydrogen ions (OH^{-} ions) is called a strong base (or strong alkali).e.g.. KOH and NaOH are a strong base.

Weak base:- A base which is partially ionised in water and thus produces a small amount of hydroxide ions (OH^{-} ions ) is called a weak base (or weak alkali).
e.g.. NH_{4}OH , \;Ca(OH)_{2} and\; Mg(OH)_{2} are weak base.

4. Choose strong and weak acids and strong and weak bases from the following-
HNO_{3}, CH_{3}COOH,\; NaOH,\; NH_{4}OH,\; KOH,\; H_{2}CO_{3}, \;Ca(OH)_{2},\; HCI
Ans:- strong acids:-HNO_{3}\;,HCl
weak acids:-CH_{3}COOH\;,H_{2}CO_{3}
strong bases:-NaOH, KOH
weak bases:-NH_{4}OH\;,Ca(OH)_{2}

5. Why we do feel a burning sensation in the stomach when we over eat? What is the medicine used called? Give one example.
Ans:- when we overeat, a large amount of HCl is released in our stomach to help us digest that food properly, which makes our stomach acidic and leads a burning sensation.
The medicine used to treat acidity is called an antacid.
e.g.. milk of magnesia (Magnesium hydroxide) is an antacid.

6. How is bleaching powder produced? Give the reaction involved.
Ans:- Bleaching powder is prepared by passing chlorine gas over dry slaked lime:-Ca(OH)_{2}+Cl_{2}\rightarrow CaOCl_{2}+H_{2}O

7. What is the basic theory of the manufacture of baking soda?
Ans:- Baking soda (or sodium hydrogen carbonate ) is manufactured on a large scale by reacting a cold and concentrated solution of sodium chlorine (called brine ) with ammonia and carbon dioxide.

8. How is plaster of Paris prepared? What reaction takes place?
Ans:- Plaster of Paris is prepared by heating gypsum (CaSO_{4}.2H_{2}O) to a temperature of100^{\cdot }C (373K) in a kiln.CaSO_{4}.2H_{2}O\xrightarrow[100c]{heat}\;CaSO_{4}.\frac{1}{2}H_{2}O+\;\frac{1}{2}H_{2}O

9. Write the chemical formulae of washing soda. What happens when crystals of washing soda are exposed to air?
Ans:-The chemical formula of washing soda is Na_{2}CO_{3}.10H_{2}O
When crystals of washing soda are exposed to air, they lose molecules of water of crystallisation and turn to white powder. This change is known as efflorescence.

10. What does “slinking of lime”‘ stand for? Write the chemical equation for the reaction involved.

Ans:- Calcium oxide CaO reacts vigorously with water produced slaked lime [Ca(OH)_{2}. This reaction is called slaking of lime.

CaO(s)+H_{2}O(l)\rightarrow Ca(OH)_{2}

11. Given the pH values of four different liquids as 7.0, 14.0, which of these could be that (i) lemon juice 4,0, 2.0 (ii) distilled water (iii) 1M sodium hydroxide solution (iv) tomato juice

Ans:-Lemon juice- 2.0

distilled water – 7.0

sodium hydroxide -14.0

tomato juice – 4.0

12. What is “baking powder”? How does it make the cake soft and spongy?

Ans:- Baking powder is a mixture of baking soda (sodium hydrogen carbonate ) and mild, edible acid such as tartaric acid.

When baking powder mixes with water for baking cake or bread, then sodium hydrogen carbonate reacts with tartaric acid to evolve CO2 gas and it gets trapped in the wet dough and bubbles out slowly making the cake or bread to rise and become soft and spongy.

13. Write the chemical formulae of bleaching powder. How is bleaching powder prepared? For what purposes it is used in paper industries.

Ans:- CaOCl2 (Calcium oxychloride)

Bleaching powder is prepared by passing chlorine gas over dry slaked lime:-Ca(OH)_{2}+Cl_{2}\rightarrow CaOCl_{2}+H_{2}O

it is used in the paper industry for bleaching wood pulp.

14. Why does tooth decay start when the PH of the mouth is lower than 5.5?

Ans:- Tooth decay starts when PH of acid formed in the mouth falls below 5.5.This is because then the acid becomes strong enough to attack the enamel of our teeth and corrode it.


  1. Why should curd be not kept in copper or brass vessels? What is done to protect it?

Ans:- Curd and sour substances contain acids. Which can react with the metels of brass and copper vessels to form toxic metel compounds which can cause food poisoning as well as  harm our body health. So curd and sour substances should be kept in Earthen pot.

  1. Comment on the statement ” All alkalies are bases but all bases are not alkalies”

Ans:-  Most of bases do not dissolve in water but some bases dissolve in water. These bases which dissolve in water without any chemical reaction are called alkali.

Therefore, all allkalies are bases but all bases are not alkalies. The common alkalies are NaOH, KOH, Ca(OH)2, Mg(OH)2 etc.

  1. What is acid rain? What is its PH? How does it affect the aquatic life?

Ans:- When the PH of water is about 5.6, it is called acid rain.

The strength of an acid or base is measured on a scale of numbers called PH scale. The PH scale has value from 0 to 14. Too much acid rain can lower the PH of lake water or river water to such an extent that the survival of aquatic life becomes difficult.

  1. (a) What is the action of litmus on-

(i) Dry ammonia gas

Ans:- There is no change in the colour of litmus paper comes in contact with dry ammonia gas since it does not release any ion.

(ii) The solution of ammonia gas in water.

Ans:- Ammonia solution turns red litmus to blue since base turns red litmus to blue.

(b) State the observations you would make on adding ammonium hydroxide to an aqueous solution of-

(i) Ferrous sulphate

Ans:-  When ammonium hydroxide is added to Ferrous sulphate solution a green coloured precipitate of Ferrous hydroxide is formed.


(ii) Aluminium chloride

Ans:- When ammonium hydroxide is added to the Aluminum chloride solution a white precipitate of Aluminum hydroxide is formed.



  1. Write any three chemical properties of acids.

Ans:-  Three Chemical properties of the metal are:-

(a) The acid reacts with metals to form hydrogen gas.


(b) The acid reacts with metal carbonates to form a salt, carbon dioxide gas and water.

For e.g. :-

(c) Acids react with base ( or alkalies) to form a salt and water is called neutralization reaction.

  1. Why bleaching powder gives a typical smell in the air?

Ans:- Since bleaching power is a yellowish white power with a strong smell of chlorine. The smell of chlorine is activated and it diffuses into the atmosphere.

  1. How will you prepare to dilute sulphuric acid from concentrated sulphuric acid? Give the reason for your answer.

Ans:- The dilution of conc. H2SO4 should always be done by adding conc. HCl to water gradually with stirring and not by adding water to conc. H2SO4 because of highly exothermic ( or heat producing), which can splash the acid on our face or clothes and cause acid burns.

  1. Name the natural source of the following acids:-

(a) Methanoic acid

Ans:- Ant sting and nettle leaf sting

(b) Citric acid.

Ans:- Lemons and oranges.

(c) Oxalic acid

Ans:- Tomatoes.

(d) Ascorbic acid.

Ans:- Mango, papaya, water, melon etc.

  1. Write down the natural sources of the following acids:-

(a) Ethanoic acid

Ans:- Vinegar (Sikra)

(b) Lactic acid

Ans:- Sour milk

(c)Tartaric acid

Ans:- Tamarinds and unripe grapes.

(d) Hydrochloric acid

Ans:- Stomach.

  1. Write down four important characteristics of acid.

Ans:- The important four characteristics of acid are:-

(a) Acid has a sour taste.

(b) The acid solution turns blue litmus to red.

(c) Acid solution contact electricity.

(d) Acids react with metals to form hydrogen gas.

(e) The acid reacts with base ( or alkalies ) to form salt and water.

(f) The acid reacts with metal oxide to form salt and water.

  1. When hydrochloric acid is added to sodium carbonate and sodium bicarbonate then production of sodium chloride and water write with a chemical reaction.

Ans:- (a) Metel carbonate + Acid  → Salt carbondioxide + water

For e.g.:-

(b) Metel hydrogen carbonate + Acid  → Salt + carbondioxide + water

For e.g.:-


  1. Mention four important characteristics of the base.

Ans:- The important four characteristics of acid are:-

(a) Bases have a bitter taste.

(b) Bases feel soapy to touch.

(c) Bases react with some metals to form hydrogen gas.

(d) Bases react with acids to form salt and water.

(e) Bases react with non-metal oxides to form salt and water.

  1. When an acid reacts with metal, what is the name of gas which is produced from this reaction? Write with a chemical reaction.

Ans:-  Acids react with metal to form hydrogen gas.


  1. What will be the colour of turmeric in acids, neutral and basic medium?

Ans:- Turmeric contains a yellow dye. It turns red in basic solution. It will retain its colour in acid and neutral. i.e. it does not change in colour.

  1. What will be the colour of litmus in acids, neutral and basic medium?

Ans:-.Litmus turns red in acidic solution and blue in basic solution.  It turns purple in neutral solution

  1. What will be the colour of phenolphthalein in acid, neutral and basic medium?

Ans:- Phenolphthalein indicator is colourless in acidic solution and pink colour in basic solution, where it does not change colour  in neutral solutions.

  1. What will be the colour of methylorange in acid, neutral and basic medium?

Ans:- In a neutral solutions methy orange is orange, in acid solution red and in basic solution yellow.

  1. Write the names of two natural indicators.

Ans:- The names of two natural indicators are China Rase and Turmeric.

  1. The H2SO4 solution is acidic but C2H5OH is not acidic, Explain with reasons.

Ans:- H2SO4 shows acidic character because it ionizes in aqueous solution to produce H+ (aq) ions. In other hand, C2H5OH ( alcohol ) does not shows acidic character because it does not ionize in aqueous solutions to produce H+ (aq) ions.

  1. Write down the name of acids and bases which is required to prepare Na2CO3 and MgSO4.


  1. What will be the action of the following substances on litmus paper?

Dry HCI gas, moistened NH3 gas, Lemon juice, Carbonated soft drink, curd, soap solution.

Ans:- (a) Dry HCI gas has no effect on litmus

(b) Moistened NH3 gas turns red litmus to blue.

(c) Lemon juice turns blue litmus to red.

(d) Carbonated soft drink turns blue litmus to red.

(e) Curd turns blue litmus to red.

(f) Soap solution turns red litmus to blue.

What happens when zinc metal is treated with a dilute solution of a strong acid, a gas evolved, Which is utilized in the hydrogenation of oil? Name the gas evolved. Write the chemical equation of the reaction involved and also write a test to detect the gas formed.

Ans:- Hydrogen gas is evolved when Zn metal reacts with dilute acids. The reaction involved is: Zn (s) + 2 HCl (aq) —>ZnCl2 (aq) + H2 (g)

Test for H2 gas: When this gas passed through a soap solution and a burning splinter is brought near the soap bubble filled with gas, it burns with a pop sound.

What happens when nitric acid is added to eggshell?

Ans:- Eggshell is made of calcium carbonate. When nitric acid is added to eggshell, it gives CO2, Ca(NO3)2 and H2O.

For making a cake, baking soda instead of baking powder in a cake. (a) How will it affect the taste of the cake and why? (b) what can baking soda be converted into baking powder? (c) What is the role of tartaric acid added to baking soda?

Ans:-(a) The cake will taste bitter due to the formation of Sodium Carbonate (Na2CO3).

(b) Tartaric acid should be added to baking soda to convert it into baking powder.

(c) Tartaric acid neutralizes the bitterness produced by the baking powder.

Write activity to show the reaction of acids with metal carbonates and metal hydrogen carbonate salts.

Ans:- 1. Take a small amount of metal carbonate in test tube A and metal bi-carbonate in test tube B.

2. Pour a few drops of H2SO4 in both the test tubes. You will notice the evolution of colorless gas.

3. Pass the evolved gas in both the test tubes through lime water, with the help of a delivery tube.

4. You will notice that lime water turns colorless in both the cases.

5. This indicates that the evolved gas is CO2.

for example:ZnCO3 (s) + H2SO4 (aq) —> ZnSO4 (aq) + CO2 (g) + H2O (l)

Similarly, Zinc hydrogen carbonate on reacting with Sulphuric acid produces Zinc Sulphate, water, and carbon dioxide as follows:

Zn(HCO3)2 (s) + H2SO4 (aq) —> ZnSO4 (aq) + 2 CO2 (g) + 2 H2O (l)

What do you mean by ionic product of water and PH value?

Ans:- The product of molar concentration of H+ and OH– ions in pure water or an aqueous solution at constant temperature is constant which is called as an ionic product of water.

PH value is 7.

Name three important mineral acids. Give two important uses of each of them.

Ans:- H2SO4 (Sulphuric acid), HCl (hydrochloric acid) & HNO3 (Nitric acid).

Uses of H2SO4 : (1) it is used in the manufacturing of  fertilizers (like ammonium sulphate)

(2) it is used in car batteries.

HCl: (1) it is used for removing oxide film from steel objects.

(2)  it is used in dye-stuffs, textile, food and leather industries.

HNO3 :  (1) it is used for making fertilizers ( like ammonium nitrate).

(2)  it is used for explosives (like TNT) , dyes and Plastic.

What is the difference between a normal salt and an acidic salt. Explain with examples.

Ans:- Normal salts are formed mainly by the neutralization process between a strong acid and a strong base.

Ex: NaCl, K2SO4 etc.

Acidic salts are formed by the neutralization process between a strong acid and a weak base. Ex: NaHCO3, KHSO4 etc.

How will you classify different types of oxides into three main categories? Explain with suitable examples.

Ans:- On the basis of their chemical behavior, there are acidic, basic and amphoteric oxide.

      1. Acidic oxide: It reacts with water and produces an acid. Usually, it is the oxide of non-metals. e.g. SO2 + H2O —> H2CO3
      2. Basic oxide: A basic oxide reacts with water to give a base. e.g. CaO + H2O —> Ca(OH)2
      3. Amphoteric oxide: It is that metallic oxide displaying a dual behavior (an acid as well as a base).It reacts with both alkalis as well as base. e.g. ZnO + 2 HCl —> ZnCl2 + H2O

How can you classify salts into different types? Give two examples of each type.

Ans:- Salts are classified into four categories on the basis of the strength of acid and base.

they are:

        1. Salt of strong acid and strong base.e.g NaCl, KCl
        2. Salt of strong acid and weak base. e.g. NH4Cl, NH4I
        3. Salt of weak acid and strong base. e.g. CH3COONa, COO Na+
        4. Salt of weak acid and weak base. e.g. CH3COO NH4+

How is common salt found in nature? Give any four important uses of common salt.

Ans:- Common salt (NaCl) occurs naturally in seawater and rock salt. Common salt occurs in dissolved form in sea water. On the other hand, common salt occurs in solid form as rock salt.

Uses of common salt:

1. It is most commonly used in cooking food (or in our diet)

2. Common salt is used as a preservative of fish, meat, and pickles.

3.common salt is used in the manufacture of soap.

4. common salt is used to melt ice which collects on the roads during winter in cold countries.


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