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Acids, Bases and Salts : Complete Set of Questions


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This set of questions contains all the possible concepts
which could be asked in the examination

Acids and Bases

Q.1 Define acid and list  its  two chemical properties?

Acids - Acids are compounds which give hydrogen ion in water solution. For example, Hydrochloric acid (HCl), Sulphuric acid(H2SO4), Nitric acid(HNO3).

Two properties of acids :

(i) Acids reacts with metal to form salt and hydrogen gas.

(ii) Acids react with metal carbonate or metal hydrogen carbonate to produce salt, carbon dioxide and water.


Q.2 What  is neutralization reaction? Give two examples?   

Neutralization Reaction 

An acid neutralizes a base when they react with each other and respective salt and water are formed.

Acid + Base → Salt + Water

Since in the reaction between acid and base both neutralize each other, hence it is also known as neutralization reaction.

Example

• Sodium chloride and water are formed when hydrochloric acid reacts with sodium hydroxide (a strong base).


• In similar way, calcium chloride is formed along with water when hydrochloric acid reacts with calcium hydroxide (a base).


Q.3 Complete the following reactions and write the name of the metallic compounds obtained :
(a) MgO + H2SO4 →

(b) Al2O3 +HCl →

(a) MgO  + H2SO4 →  MgSO4 + H2O

(b) Al2O3 + 6HCl → 2AlCl3 + 3H2O                                     


Q.4 List in tabular form two differences between an acid and a base based on their chemical properties?   


Q.5 Give reason, why aqueous-solution of an acid conducts electricity?

When acids dissolved in water they produce H+ ions and due to formation of these mobile ions in aqueous solution of acids, it conducts electricity.


Q.6 A solution reacts with crushed egg shells to give a gas that turns lime water milky, name the gas evolved?

The egg shells are made up of CaCOand the gas which turns lime water milky is carbon dioxide.


Q.7 How will you test for the gas which is liberated when hydrochloric acid reacts with an active metal?

When an active metal reacts with hydrochloric acid, Hydrogen gas is liberated. We will test the presence of hydrogen gas by bringing a burning candle near the mouth of the test tube in which the reaction is taking place if the gas burns with a popping sound, then it can be concluded that it is a Hydrogen gas.


Q.8 Name the gas evolved when dilute hydrochloric acid reacts with sodium hydrogen carbonate. How is it recognized ?

When dilute hydrochloric acid reacts with sodium hydrogen carbonate, Carbon dioxide gas is liberated .We recognize the presence of carbon dioxide by passing it through lime water which turns milky or a white precipitate of calcium carbonate is formed. This confirms that the gas is carbon dioxide.


Q.9  Explain strong acids and weak acids with examples?

Strong acids ionize fully in water to produce large number of H+ ions. For example, Hydrochloric acid (HCl), Sulphuric acid(H2SO4), Nitric acid(HNO3), Hydrobromic acid(HBr).

Weak acids ionize partially in water to produce small number of H+ ions. For example, carbonic acid(H2CO3), phosphoric acid(H3PO4), sulphurous acid(H2SO3), acetic acid(CH3COOH).


Q.10 How is the concentration of hydronium ions (H3O+) affected when the solution of an acid is diluted ?

• If concentrated acid (or base) is mixed with water, concentration of hydronium ions H_3^ + O decreases. So the acid or base becomes dilute.

• The phenomena of changing concentrated acid / base into dilute acid / base (respectively) is an exothermic reaction.


Q.11 Write word equation and then balanced equations for the reactions 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 aluminum  powder.

(d) dilute hydrochloric acid reacts with iron filings.

(a) {H_2}S{O_4}\left( {aq} \right) + Zn\left( s \right) \to ZnS{O_4}\left( {aq} \right) + {H_2}\left( g \right)

(b) 2HCl\left( {aq} \right) + Mg\left( s \right) \to MgC{l_2}\left( {aq} \right) + {H_2}\left( g \right)

(c) 2{H_2}S{O_4}\left( {aq} \right) + 2Al\left( s \right) \to A{l_2}{\left( {S{O_4}} \right)_3}\left( {aq} \right) + 3{H_2}\left( g \right)

(d) 6HCl\left( {aq} \right) + 2Fe\left( s \right) \to 2FeC{l_3}\left( {aq} \right) + 3{H_2}\left( g \right) 


Q.12 Complete and balance the following chemical equations

(a) Zn (s) + HCl (aq)

(b) Na2CO3 (s) + HCl (aq)

(c) NaHCO3 (s) + HCl (aq)

(d) NaOH (aq) + HCl (aq)

(e) CuO(s)  + HCl (aq)→

(a) Zn(s) + 2HCl (aq) → ZnCl2(aq) + H2(g)

(b) Na2CO3(s) + 2HCl (aq) → 2NaCl (aq) + CO2 (g) + H2O (l)

(c) NaHCO3 (s) + HCl(aq) → NaCl(aq) + H2O (l) + CO2 (g)

(d) NaOH(aq) + HCl(aq) → NaCl(aq) + H2O (l)

(e) CuO (s) + 2HCl (aq)  → CuCl2 (aq) + H2O (l)


Q.13  What happens when an acid reacts with metal ? Give chemical equation of the reaction involved?

Reaction of acids with metal -

Acids give hydrogen gas along with respective salt when they react with a metal. 

Example :

• Hydrogen gas and zinc chloride are formed when hydrochloric acid reacts with zinc metal.

Zn + 2HCl\left( I \right) \to ZnC{l_2}\left( s \right) + {H_2}


Q.14 While diluting an acid/base , why is it recommended that the acid should be added to water and not water to the acid/base ?

• Always add concentrated acid/base to water; not water to concentrated acid/base.

• When concentrated acid is added to water, heat is released gradually. This heat is absorbed by large amount of water to increase its temperature.

• When water is added to concentrated acid, heat is released suddenly. This heat vaporizes small amount of water to steam. This steam is splits out with drops of concentrated acid which can damage our body. So always add concentrated acid to water, not water to concentrated acid. Same is true with base also.


Q.15 What happens when an acid reacts with a base ? Explain by taking the example of hydrochloric acid and sodium hydroxide. Give equation of the chemical reaction which takes place. What is the special name of such a reaction ?

An acid neutralizes a base when they react with each other and respective salt and water are formed.

Acid + Base → Salt + Water

Since in the reaction between acid and base both neutralize each other, hence it is also known as neutralization reaction.

Example:

• Sodium chloride and water are formed when hydrochloric acid reacts with sodium hydroxide (a strong base).


 Q.16 What happens when an acid reacts with a metal oxide ? Explain with the help of an example. Write a balanced equation for the reaction involved.

Acids give water along with respective salt when they react with a metal oxide.

Metal + acid → Respective salt + Water

Example :

• Water and sodium chloride are formed when hydrochloric acid reacts with sodium oxide.

Na2O + 2HCl (aq)→ 2NaCl + H2O


Q.17 Name one natural source of each of the following acids :

(a) Citric acid

(b) Oxalic acid

(c) Lactic acid

(d) Tartaric acid



Q.18 Name one animal and one plant whose stings contain formic acid (or methanoic acid ).     

Animal sting containing formic acid: Ant sting
Plant sting containing formic acid: Nettle leaf sting


Q.19 (a) What are organic acids and mineral acids ?

(b) Give two examples each of organic acids and mineral acids.

(c) State some of the uses of mineral acids in industry.

(a) Organic acids: An organic acid is an acid that is found naturally in plants and animals. Generally organic acids are weak acids and do not dissociate completely in water.

Mineral acids : Mineral acids are man-made and are derived from one or more inorganic compounds. They are also known as inorganic acids. They range from acids of great strength to those that are very weak.

(b) Here are a few common examples:

Organic acids:

Lactic acid

Citric acid

Mineral acids:

Hydrochloric acid (HCl)

Nitric acid (HNO3)

(c)Uses of mineral acids in industry :

Mineral acids are used in many sectors of the chemical industry for the synthesis of various chemicals.

Dilute  solutions of hydrochloric acid are used for removing the deposits form inside boilers, with precautions to prevent the corrosion of the boilers by the acid.

They are also used in the processing of leather, purification of common salt, construction of buildings, etc.


Q.20 Classify the following into strong acids and weak acids :

HCl, CH3COOH, H2SO4, HNO3, H2CO3, H2SO3

Strong acid – HCl, H2SO4, HNO3

Weak acid – CH3COOH, H2CO3, H2SO3   


Q.21 Why do HCl, H2SO4, HNO3, etc, show acidic character in aqueous solutions while solutions of compounds like C6H12O6 (glucose) and C2H5OH (alcohol) do not show acidic character ?

HCl, H2SO4 , HNO3 etc. show acidic character in aqueous solutions, whereas solutions of compounds such as C6H12O6 (glucose) and C2H5OH (alcohol) do not show acidic character because HCl, H2SO4, HNO3, etc. dissociate in aqueous solutions to give H+ (aq) ions, which are a vital part of an acid and determine the acidic property of acids.
C6H12O6 (glucose) and C2H5OH (alcohol) do not dissociate in aqueous solution even though they contain hydrogen atoms.


Q.22 Why acid is not stored in metallic containers. Give reason?

Acid is not stored in metallic containers because acids and metals can easily react. Acids react with metals to give hydrogen gas.Curd and other foodstuffs (such as lemon juice) are acidic in nature. Hence, when these acidic foodstuffs are  kept in metal containers, hydrogen gas is liberated , and it spoils food.


Q.23 Name the gas evolved when zinc granules are treated / heated with:

(a) hydrochloric acid solution

(b) sodium hydroxide solution

(a) When zinc granules are treated with hydrochloric acid, zinc chloride is formed and hydrogen gas is liberated

Zn (s) + 2HCl(aq) → ZnCl2(aq) + H2(g)

(b) Zinc reacts with sodium hydroxide giving sodium zincate and hydrogen gas

Zn (s) + 2NaOH(aq) → Na2ZnO2(aq) + H2(g)   


Q.24 What is the common name of  water soluble bases ? 

Water soluble bases are commonly known as alkalies. An alkali is a unique base that dissolves in water without any chemical reaction. All alkalies are bases whereas only some bases are alkalies.


Q.25 Which chemical is injected into the skin of a person :

(a) during an bee sting ?

(b) during the wasp sting ?

How can the effect of these stings be neutralized?

(a) When a bee stings a person, it injects an acidic solution into the person’s skin. This causes severe pain and irritation. The remedy is to apply a baking soda solution which is a basic in nature. The solution relief's the pain by neutralizing the acid.

(b) When a wasp stings a person, it inserts an alkaline solution into the person’s skin. This causes severe pain  and irritation. The remedy is to apply a weak acid, such as vinegar, to the wound.. The acid neutralizes the alkaline solution and relief the pain.


Q.26 (a) Define an acid and a base. Give two examples of each.

(b) Give the names and formulas of two strong bases and two weak bases.

(c) What type of ions are formed :

(i) When an acid is dissolved in water ?

(ii) When a base  is dissolved in water ?

(d) Write the neutralization reaction between acids and bases in terms of the ions involved.

(e) Write any two important uses of bases. 

(a) Acids – Acids are compounds which give hydrogen ion in water solution. For example, Hydrochloric acid HCl), Sulphuric acid (H2SO4), Nitric acid (HNO3).

Bases – Bases are compounds which give hydroxide ion in water solution. For example, Sodium hydroxide (NaOH), Potassium hydroxide (KOH), Calcium hydroxide (Ca(OH)2)

(b) Strong bases ionize fully in water  to produce large number of OH– ions. For example, sodium hydroxide (NaOH), potassium hydroxide (KOH), lithium hydroxide (LiOH) and Calcium hydroxide (Ca(OH)2).

NaOH(aq) → Na+ +OH–

Weak bases ionize partially in water to produce small number of OH– ions. For example magnesium hydroxide (Mg(OH)2), ammonium  hydroxide (NH4OH).

(c) The type of ions formed are explained below

(i) When an acid is dissolved in water, it ionises to produce hydronium ions (H3O+)

(ii) When a base is dissolved in water, it ionises to produce hydrogen ions (OH+ ions)

(d)   Neutralization Reaction –

An acid neutralizes a base when they react with each other and respective salt and water are formed

Acid + Base → Salt + Water

Since in the reaction between acid and base booth neutralize each other, hence it is also known as neutralization reaction.

Equations involving ions :

Hydrochloric acid ionises in water as follows

HCl (aq) → H+(aq) + Cl(aq)

Sodium hydorxide ionises in water as

NaOH(aq) → Na+(aq) + OH+(aq)

Let us now combine both the reactions above

Na+(aq)  + Cl(aq) + H+(aq) + OH(aq)  NaCl(aq) + H2O(l)

(e) Two important uses of base:

Sodium hydroxide (base) is used to form soap, paper and fibre.

Calcium hydroxide (base) is used in bleaching powder.


Q.27 What happens when bases react with non-metal oxides?  Explain with the help of an example. What does this reaction tell us about the nature of non-metal oxides?

Reaction of bases with non-metal Oxides :

Non-metal oxides is a chemical compound that contains oxygen and one non-metal in its chemical formula. For example, carbon dioxide (CO2), sulphuric dioxide (SO2).

Bases react with non-metal oxides to form a salt and water

Bases + Non-metal oxides  → Salt + Water

Example :

2NaOH(aq) + CO2(g) → Na2CO3(aq) + H2O(l)

Here, sodium hydroxide (base) reacts with carbon dioxide (non-metal oxide) to give sodium carbonate (salt) and water.

This reaction tell us that non-metal oxides are acidic in nature.


Q.28 Write down various uses of acids and bases?

Uses of Acids and Bases :

Sulphuric acid is used to make fertilizers, dyes, chemicals, plastics, fibres, detergent, explosives, car batteries.

Nitric acids is used to make fertilizers, explosives (TNT – Tri Nitro Toluene), dyes, plastics.

Hydrochloric acid is used to form dye, in textile industry, food and leather industry, removing metal oxide films from steel objects.

Sodium hydroxide (base) is used to form soap, paper, fibre.

Calcium hydroxide (base) is used in bleaching powder.


Q.29 Write down the types of acids on the basis of their occurrence with example?

Types of Acids :

Acids can be divided into two types on the basis of their occurrence –

(i) Natural acids

(ii) Mineral acids

Natural Acid : Acids which obtained from natural sources (plants and animals) are called natural acid or organic acid.

Mineral Acids : Acids that prepare from mineral are known as mineral acids/inorganic acids/man-made acids or synthetic acid, such as hydrochloric acid (HCl), sulphuric acid (H2SO4), nirtic acid (NHO3), etc. 


Q.30  What happen when base react with metal, explain it with example?

Reaction of Base with metal :

When base react with metal, it produces salt and hydrogen gas.

Alkali + metal → Respective salt + hydrogen gas

Example :

Sodium hydroxide gives hydrogen gas and sodium zincate when reacts with zinc metal.

2NaOH\left( {aq} \right) + Zn\left( s \right) \to N{a_2}Zn{O_2}\left( {aq} \right) + {H_2}


Q.31 Explain the reaction of carbonates and bicarbonates with acids?

Reaction of Carbonates with Acids:

Acids give carbon dioxides gas and respective salts along with water when they react with carbonates.

Carbonate + acid → Salt + carbon dioxide + water

Examples :

Hydrochloric acid gives carbon dioxide gas, sodium chloride along with water when reacts with sodium carbonate.

N{a_2}C{a_3} + 2HCl \to 2NaCl + C{O_2} + {H_2}O

Reaction of Acid with Bicarbonates –

Acids give carbon dioxide gas, respective salt and water when they react with bicarbonate.

Acid + bicarbonate →  Salt + carbon dioxide + water

Examples :

Hydrochloric acid gives carbon dioxide, sodium chloride and water when it reacts with sodium bicarbonate.

NaHC{O_3} + HCl \to NaCl + C{O_2} + {H_2}O

In general, if we use weak acids, reaction will be slow and if we use strong acids, reactions will be fast.


Q.32 Like acids, compounds such as alcohol and glucose also contain hydrogen but these compounds are not categorized as acids. Why?

Substances which contains hydrogen are considered to be acids. Acids when dissolved in water produce H+ ions. But glucose and alcohol do not produce H+   ions when dissolved in water. So, they are not categorized as acids.


Q.33 Describe an activity with labeled diagram to show how acid and base react with metal?

Experiment to Show how do Acid and Base react with Metal : 

• Set apparatus as above

• Take zinc granules in a test tube and put dilute suphuric acid in it

• You will see small bubbles of hydrogen gas in test tube

• Pass the gas through soap solution.

• Soap bubble will be formed with the gas inside.

• Take a burning candle near bubbles.

• If the candle burns with pop sound, then it confirms the evolution of hydrogen gas. Burning with pop sound is the characteristic test for hydrogen gas.


Q.34 Describe an activity how metal oxides react with acid?

• Take small amount of black copper oxide in a test tube.

• Pour some dilute HCl slowly in test tube.

• Keep stirring.

• We observe a bluish – green solution due to formation of copper chloride.


Q.35 What happens when carbon-dioxide gas is passed through lime water for a short time?Write equations of the reactions involved.

When carbon dioxide gas is passed through lime water, the lime water turns milky. This confirms that the gas liberated in the reaction is none other than carbon dioxide.

The reaction that occurs when carbon dioxide is passed through lime water for a short time can be represented as follows :

Ca(OH)2(aq) + CO2(g) → CaCO3(s) + H2O(l)


Q.36 Explain the corrosive nature of acids and bases?

Corrosive Nature of Acids and Bases –

Acids and bases are corrosive in nature. They damage / destroy the substances with which they come into contact.

Strong acids and bases are more corrosive while weak acids and bases are less corrosive.

Specially concentrated weak acids and bases are not corrosive.

Generally Dilute weak acids and bases are not corrosive. Dilute acids are found in fruits and vegetable and we eat them in our meal because they are not corrosive. But concentrated weak acids and bases are corrosive in nature.

This symbol is used to warn us for corrosive substances.


Q.37 Explain how, several monuments like Tajmahal become yellowish due to acid rain?

Acid rain causes damage to the historical monuments and other buildings. For example Tajmahal, which is made of marble, is getting damaged because of reaction with acid rain. Marble is calcium carbonate which reacts with the acid and thus gets corroded.


Q.38 Explain the behavior of acids and bases in the absence of water?

Acids and Bases in absence of Water:

A dry acid does not dissociate in hydrogen ions. When we dissolve it with water, then it shows the acidic behavior.

For example, dry hydrochloric acid (gas) does not change the colour of blue litmus paper to red because a dry acid does not dissociate hydrogen ion. This is the cause that a moist litmus paper is used to check the acidic or basic character of a gas.

Similarly at room temperature, sodium hydroxide is in the form of solid. So as a solid, NaOH does not dissociate into hydroxide ion. When we dissolve it with water, then it shows its basic behavior.



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