Lakhmir Singh solutions for Chemistry [English] Class 10 chapter 2 - Acids, Bases and Salts [Latest edition]

What colour does the following indicator turn when added to a base or alkali (such as sodium hydroxide)?

Methyl orange

What colour does the following indicator turn when added to a base or alkali (such as sodium hydroxide)?

Litmus

What colour does the following indicator turn when added to a base or alkali (such as sodium hydroxide)?

Red cabbage extract

What colours does the following indicator turn when added to an acid (such as hydrochloric acid)?

Litmus

What colours does the following indicator turn when added to an acid (such as hydrochloric acid)?

Methyl orange

Name an indicator which is red in acid solution but turns blue in basic solution.

Name an indicator which is pink in alkaline solution but turns colourless in acidic solution.

When a solution is added to vanilla extract, then the characteristic smell of vanilla cannot be detected. State whether the given solution is an acid or a base.

Name the gas evolved when dilute HCl reacts with sodium hydrogencarbonate. How is it recognised?

Give the names and formulae of two strong acids.

Give the names and formulae of two weak acids.

Name one natural source of the following acid:

Citric acid

Name one natural source of the following acid:

Oxalic acid

Name one natural source of the following acid:

Lactic acid

Name one natural source of the following acid:

Tartaric acid

Name one animal whose stings contain formic acid (or methanoic acid).

Name one plant whose stings contain formic acid (or methanoic acid).

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

Write a word equation and then a balanced equation for the reaction taking place when:

Dilute sulphuric acid reacts with zinc granules.

Write a word equation and then a balanced equation for the reaction taking place when:

Dilute hydrochloric acid reacts with magnesium ribbon.

Write a word equation and then a balanced equation for the reaction taking place when:

Dilute sulphuric acid reacts with aluminium powder.

Write a word equation and then a balanced equation for the reaction taking place when:

Dilute hydrochloric acid reacts with iron filings.

Complete and balance the following chemical equation:

\[\ce{Zn_{(s)} + HCl_{(aq)} ->}\]

Complete and balance the following chemical equation:

\[\ce{Na2CO3_{(s)} + HCl_{(aq)} ->}\]

Complete and balance the following chemical equation:

\[\ce{NaHCO3_{(s)} + HCl_{(aq)} ->}\]

Complete and balance the following chemical equation:

\[\ce{NaOH_{(aq)} + HCl_{(aq)} ->}\]

Complete and balance the following chemical equation:

\[\ce{CuO_{(s)} + HCl_{(aq)} ->}\]

Acids have a ______ taste and they turn ______ litmus to ______.

Substances do not show their acidic properties without ______.

Acids produce ______ ions on dissolving in water.

Those substances whose smell (or odour) changes in acidic or basic solutions are called ______ indicators.

Onion and vanilla extract are ______ indicators.

What is an indicator?

Name three common indicators.

Name the acid-base indicator extracted from lichen.

What colour does the turmeric paper turn when put in an alkaline solution?

Name two olfactory indicators. What is the effect of adding sodium hydroxide solution to these olfactory indicators?

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

Which gas is usually liberated when an acid reacts with a metal? How will you test for the presence of this gas?

What happens when dilute hydrochloric acid is added to sodium carbonate? Write a balanced chemical equation of the reaction involved.

Which gas is liberated when dilute hydrochloric acid reacts with sodium carbonate? How will you test for the presence of this gas?

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?

What are organic acids?

What are mineral acids?

Give two examples of organic acids.

Give two examples of mineral acids.

State some of the uses of mineral acids in industry.

What is meant by strong acids?

What is meant by the term weak acid?

Classify the following into strong acids and weak acids:

HCl, CH₃COOH, H₂SO₄, HNO₃, H₂CO₃, H₂SO₃

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?

Give the chemical equation of the neutralisation reaction which takes place.

Why should curd and other sour foodstuffs (like lemon juice, etc.) not be kept in metal containers (such as copper and brass vessels)?

What is produced if an acid is added to a base?

Dry HCl gas does not change the colour of dry blue litmus paper. Why?

Why do acids not show acidic behaviour in the absence of water?

Why does an aqueous solution of an acid conduct electricity?

Why does distilled water not conduct electricity whereas rain water does?

What happens when an acid reacts with a metal carbonate? Explain with the help of an example.

Write a chemical equation of the reaction involved when an acid reacts with a metal carbonate.

What happens when carbon dioxide gas is passed through lime water for a short time?

Write the equation of the reaction involved.

What happens when carbon dioxide gas is passed through lime water for a considerable time?

Write the equation of the reaction involved.

Which element is common to all acids?

Compounds such as alcohol and glucose also contain hydrogen but are not categorised as acids. Describe an activity to prove it.

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:

Which of the following types of medicine is used for treating indigestion caused by over-eating?

A solution reacts with marble chips to produce a gas which turns lime water milky. The solution contains ______.

One of the following is not an organic acid. This is:

The property which is not shown by acids is:

The indicators which turn red in acid solution are ______.

The discomfort caused by indigestion due to overeating can be cured by taking ______.

The property which is common between vinegar and curd is that they ______.

The indicator which produces a pink colour in an alkaline solution is ______.

A solution reacts with zinc granules to give a gas which burns with a ‘pop’ sound. The solution contains ______.

When a piece of limestone reacts with dilute HCl, a gas X is produced. When gas X is passed through lime water then a white precipitate Y is formed. On passing excess of gas X, the white precipitate dissolves forming a soluble compound Z.

1. What are X, Y and Z?
2. Write equations for the reactions which take place:
   1. When limestone reacts with dilute HCl.
   2. When gas X reacts with lime water to form white precipitate Y.
   3. When excess of gas X dissolves white precipitate Y to form a soluble compound Z.

If someone is suffering from the problem of acidity after overeating, which of the following would you suggest as remedy?

Lemon juice, Vinegar, Baking soda solution

Give reason for your choice.

On adding dilute hydrochloric acid to copper oxide powder, the solution formed is blue-green.

1. Predict the new compound formed which imparts a blue-green colour to solution.
2. Write a balanced chemical equation of the reaction which takes place.
3. On the basis of the above reaction, what can you say about the nature of copper oxide?

A white shirt has a yellow stain of curry. When soap is rubbed on this shirt during washing, the yellow stain turns reddish-brown. On rinsing the shirt with plenty of water, the reddish-brown stain turns yellow again.

1. Name the natural indicator present in curry stain.
2. Explain the changes in colour of this indicator which take place during washing and rinsing the shirt.
3. What is the nature of soap (acidic/basic) as shown by the indicator present in curry stain?

You have been provided with three test-tubes. One of these test-tubes contains distilled water and the other two contain an acidic and a basic solution respectively. If you are given only blue litmus paper, how will you identify the contents of each test-tube?

A substance X which is used as an antacid reacts with dilute hydrochloric acid to produce a gas Y which is used in one type of fire-extinguisher. Name the substance X and gas Y. Write a balanced equation for the chemical reaction which takes place.

What happens to the H⁺ ions, of the solution, when an acid is neutralised?

What happens to the temperature of the solution when an acid is neutralised?

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

Hydrochloric acid solution

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

Sodium hydroxide solution

What is the common name of water soluble bases?

What is the pH of a neutral solution?

Which is more acidic?

A solution of pH = 2 or a solution of pH = 6.

Which is more basic (or more alkaline)? 

A solution of pH = 8 or a solution of pH = 11.

Name the indicator which can give us an idea of how strong or weak an acid or base is.

The pH of soil A is 7.5 while that of soil B is 4.5. Which of the two soils, A or B, should be treated with powdered chalk to adjust its pH and why?

What is the name of the indicator which can be used for testing the pH of a solution?

What colour will the universal indicator show if you add it to the following substance?

Potassium hydroxide, pH = 12

What colour will the universal indicator show if you add it to the following substance?

Soda water, pH = 5

What colour will the universal indicator show if you add it to the following substance?

Sulphuric acid, pH = 2

A beaker of concentrated hydrochloric acid has a pH of 1. What colour will full range universal indicator turn if it is added to this beaker? Is it a strong or a weak acid?

Two solutions X and Y are tested with universal indicator. Solution X turns orange whereas solution Y turns red. Which of the solutions is a stronger acid?

Two solutions A and B have pH values of 3.0 and 9.5 respectively. Which of these will turn litmus solution from blue to red and which will turn phenolphthalein from colourless to pink?

Two drinks P and Q gave acidic and alkaline reactions, respectively. One has a pH value of 9 and the other has a pH value of 3. Which drink has the pH value of 9?

Acids have a pH ______ than 7.

Alkalis have a pH ______ than 7.

Neutral substances have a pH of ______.

The more acidic a solution, the ______ the pH.

The more alkaline a solution, the ______ the pH.

Fresh milk has a pH of 6. When it changes into curd (yogurt), will its pH value increase or decrease? Why?

What is a universal indicator?

For what purpose universal indicator is used?

How does a universal indicator work?

Water is a neutral substance. What colour will you get when you add a few drops of universal indicator to a test-tube containing water?

Which chemical is injected into the skin of a person during an ant’s sting?

How can the effect of these stings be neutralised?

Which chemical is injected into the skin of a person during the nettle leaf hair sting?

How can the effect of this sting be neutralised?

Explain the pH change as the cause of tooth decay.

How can tooth decay caused by pH change be prevented?

Explain how pH change in the lake water can endanger the lives of aquatic animals (like fish).

What can be done to lessen the danger to the lives of aquatic animals in the lake?

What happens during a bee sting? What is its remedy?

What happens during a wasp sting? What is its remedy?

Why is it wrong to treat a bee sting with vinegar?

Why is it wrong to treat a wasp sting with baking soda solution?

What does the pH of a solution signify?

Three solutions A, B and C have pH values of 6, 4 and 10 respectively. Which of the solutions is highly acidic?

A farmer has found that the pH of soil in his fields is 4.2. Name any two chemical materials which he can mix with the soil to adjust its pH.

The pH values of six solutions A to F are given below:

A = 0, B = 11, C = 6, D = 3, E = 13, F = 8

Which of the above solutions are

1. acids
2. alkalis?

Name the acids or alkalis used to make explosives.

Name the acids or alkalis used to make soaps.

Name the acids or alkalis used to make fertilisers.

The pH of a cold drink is 5. What will be its action on blue and red litmus solutions?

What is meant by strong bases?

What is meant by weak bases?

What ions are present in the solution of the following substance? (write the symbols only)

Hydrochloric acid

What ions are present in the solution of the following substance? (write the symbols only)

Nitric acid

What ions are present in the solution of the following substance? (write the symbols only)

Sulphuric acid

What ions are present in the solution of the following substance? (write the symbols only)

Sodium hydroxide

What ions are present in the solution of the following substance? (write the symbols only)

Potassium hydroxide

What ions are present in the solution of the following substance? (write the symbols only)

Magnesium hydroxide

What would you expect the pH of pure water to be?

What colour would the universal indicator show in an aqueous solution of sugar? Why?

What do you think will be the pH in the stomach of a person suffering from indigestion: less than 7 or more than 7?

What do you think will be the pH of an antacid solution?

Less than 7 or more than 7.

How does an antacid work?

Separate the following into substances having pH values above and below 7. How do these influence litmus paper?

1. Lemon juice
2. Solution of washing soda
3. Toothpaste
4. Vinegar
5. Stomach juices

Do basic solutions also have \[\ce{H+_{( aq)}}\] ions? If yes, then why are they basic?

Define an acid.

Define a base.

Give two examples of acid.

Give two examples of a base.

Give the names and formulae of two strong bases.

Give the names and formulae of two weak bases.

What type of ions are formed?

When an acid is dissolved in water.

What type of ions are formed?

When a base (or alkali) is dissolved in water.

Write the neutralisation reaction between acids and bases in terms of the ions involved.

What happens when zinc granules are heated with sodium hydroxide solution? Write the equation of the reaction which takes place.

What effect does the concentration of \[\ce{H+_{( aq)}}\] ions have on the nature of a solution?

What effect does the concentration of OH⁻ ions have on the nature of a solution?

Someone put some universal indicator paper into vinegar. The pH is 3. What does this tell you about the vinegar?

Someone put some universal indicator paper onto wet soap. The pH is 8. What does this tell you about the soap?

State whether a solution is acidic, alkaline or neutral if its pH is:

9

State whether a solution is acidic, alkaline or neutral if its pH is:

4

State whether a solution is acidic, alkaline or neutral if its pH is:

7

State whether a solution is acidic, alkaline or neutral if its pH is:

1

State whether a solution is acidic, alkaline or neutral if its pH is:

10

State whether a solution is acidic, alkaline or neutral if its pH is:

3

One of the following is a medicine for indigestion. This is:

Bee sting contains ______.

Wasp sting contains ______.

One of the following does not inject an acidic liquid into the skin through its sting. This is:

A solution turns red litmus blue. Its pH is likely to be ______.

A solution turns blue litmus red. Its pH is likely to be ______.

A solution turns phenolphthalein indicator pink. The most likely pH of this solution will be ______.

The colour of methyl orange indicator in a solution is yellow. The pH of this solution is likely to be ______.

Bee stings can be treated with ______.

Wasp stings can be treated with ______.

It has been found that rubbing vinegar on the stung area of the skin of a person gives him relief. The person has been stung by ______.

Fresh milk has a pH of 6. When milk changes into curd, the pH value will ______.

The acid produced naturally in our stomach is ______.

The daffodil plants grow best in a soil having a pH range of 6.0 to 6.5. If the soil in a garden has a pH of 4.5, which substance needs to be added to the soil in order to grow daffodils?

A milkman adds a very small amount of baking soda to fresh milk.

1. Why does he shift the pH of the fresh milk from 6 to slightly alkaline?
2. Why does this milk take a long time to set as curd?

Which of the following elements would form oxides which would indicate pH values less than seven, using moist pH paper?

Magnesium, Carbon, Sulphur, Hydrogen, Copper

The pH values of five solutions A, B, C, D and E are given below:

Which solution is

1. weakly alkaline
2. neutral
3. strongly acidic
4. strongly alkaline, and
5. weakly acidic?

Potatoes grow well on Anhad’s farm which has soil with a pH of 5.5. Anhad decides to add lot of lime to soil so that he can grow broccoli in the same farm:

1. Do potatoes grow better in acidic or alkaline soil?
2. Does broccoli grow better in acidic or alkaline soil?

Here are some results of solutions tested with universal indicator paper:

Arrange the solutions in order of their increasing pH values (starting with the one with the lowest pH).

Solution A turns universal indicator blue to purple whereas solution B turns universal indicator orange to red.

1. What will be the action of solution A on litmus?
2. What will be action of solution B on litmus?
3. Name any two substances which can give solutions like A.
4. Name any two substances which can give solutions like В.
5. What sort of reaction takes place when solution A reacts with solution В?

A first-aid manual suggests that vinegar should be used to treat wasp stings and baking soda for bee stings. What does this information tell you about the chemical nature of:

1. wasp stings?
2. bee stings?

Explain why the pH in a person’s mouth becomes lower after each meal.

What damage could be caused while the pH in a person’s mouth is low?

How could the person change his eating habits to lessen chances of suffering from tooth decay?

A group of students measured the pH of some substances they found in their homes. Their results are given in the following table:

1. What would the students have used to measure the pH?
2. Which solution is the most acidic?
3. Which solution is the most alkaline?
4. Which solutions are neutral?
5. Which solution can be used to treat wasp stings?
6. Which solution can be used to treat bee stings?

Hydrochloric acid reacts with a metal X to form a gas Y which burns with a ‘pop’ sound. Sodium hydroxide solution also reacts with the same metal X (on heating) to form the same gas Y.

1. Name X and Y.
2. Write the chemical equation of the reaction of metal X with
   1. hydrochloric acid, and
   2. sodium hydroxide solution.

What is the chemical formula of  washing soda?

What is the chemical formula of baking soda?

Write the chemical formula of soda ash.

Write the chemical formula of sodium carbonate decahydrate.

State whether the following statement is true or false:

Copper sulphate crystals are always wet due to the presence of water of crystallisation in them.

Which of the following salt has a blue colour and why?

CuSO₄.5H₂O or CuSO₄

State the common and chemical names of the compound formed when plaster of Paris is mixed with water.

Name the product formed when Cl₂ and H₂ produced during the electrolysis of brine are made to combine.

Name a calcium compound which hardens on wetting with water.

Name a sodium compound which is a constituent of many dry soap powders.

Name the metal whose carbonate is known as washing soda.

What is the common name of Na₂CO₃.10H₂O?

Write the chemical name and formula of common salt.

What are the two main ways in which common salt (sodium chloride) occurs in nature?

During the electrolysis of a saturated solution of sodium chloride, where is:

Chlorine formed?

During the electrolysis of a saturated solution of sodium chloride, where is:

Hydrogen formed?

During the electrolysis of a saturated solution of sodium chloride, where is:

Sodium hydroxide formed?

Common salt is obtained from sea-water by the process of ______.

Rock salt is mined just like ______.

Chemical formula of washing soda is ______.

Sodium hydrogencarbonate is ______ soda whereas sodium carbonate is ______ soda.

The chemical formula of plaster of Paris is ______.

Complete and balance the following chemical equation:

\[\ce{NaCl_{(aq)} + H2O_{(l)} ->[Electricity]}\]

Complete and balance the following chemical equation:

\[\ce{NaHCO3 ->[Heat]}\]

Complete and balance the following chemical equation:

\[\ce{NaCl + NH3 + H2O + CO2 ->}\]

Complete and balance the following chemical equation:

\[\ce{Ca(OH)2 + Cl2 ->}\]

What is washing soda?

State two properties of washing soda.

Give two important uses of washing soda.

Write the formula of sodium chloride.

Write the formula of the following compound:

Sodium carbonate

Explain why an aqueous solution of sodium chloride is neutral but an aqueous solution of sodium carbonate is basic (or alkaline). Write chemical equations of the reactions involved.

Write the chemical formula of ammonium chloride.

What is baking soda?

Write the chemical name of baking soda.

Give two important uses of baking soda.

How does baking soda differ chemically from washing soda?

What is meant by “water of crystallisation” in a substance? Explain with an example.

How would you show that blue copper sulphate crystals contain water of crystallisation?

Explain how anhydrous copper sulphate can be used to detect the presence of moisture (water) in a liquid.

What is the common name of sodium hydrogencarbonate?

What happens when a solution of sodium hydrogencarbonate is heated? Write equation of the reaction involved.

What will happen if heating is not controlled while preparing plaster of Paris?

Write an equation to show the reaction between plaster of Paris and water.

What happens when copper sulphate crystals are heated strongly? Explain with the help of an equation.

Name two constituents of baking powder.

How does baking powder differ from baking soda?

What is the chemical name of bleaching powder?

What is the chemical formula of bleaching powder?

What are the materials used for the preparation of bleaching powder?

Name the sodium compound which is used for softening hard water.

Which compound of calcium is used for disinfecting drinking water supply?

Name a metal compound which has detergent properties (cleansing properties).

Name one compound of calcium which is used for removing the colour of a coloured cloth.

State a peculiar (or remarkable) property of plaster of Paris.

What is gypsum?

What is gypsum?

Name a sodium compound which is used for making borax and glass.

Name the compound which is used in hospitals for setting fractured bones.

What is “baking powder”?

State two uses of the following compound:

Sodium hydroxide

State two uses of the following compound:

Chlorine

State two uses of the following compound:

Hydrogen

What is the common name of the compound CaOCl₂?

Name the raw material used for the preparation of plaster of Paris.

Which property of plaster of Paris is utilised in making casts for broken limbs in hospitals?

What happens when a concentrated solution of sodium chloride (brine) is electrolysed? Write the equation of the reaction involved.

Why is the electrolysis of a concentrated solution of sodium chloride known as chlor-alkali process?

Describe how washing soda is produced starting from sodium chloride (common salt). Write equations of all the reactions involved.

State whether an aqueous solution of washing soda is acidic or alkaline. Give reason for your answer.

What is meant by saying that washing soda has detergent properties?

Give two important uses of washing soda.

What is bleaching powder?

How is bleaching powder prepared? Write a chemical equation of the reaction involved in the preparation of bleaching powder.

What happens when bleaching powder reacts with dilute sulphuric acid? Give equation of the reaction involved.

What is plaster of Paris?

What is plaster of Paris?

How is plaster of Paris prepared? Write a chemical equation of the reaction involved.

Plaster of Paris should be stored in a moisture-proof container. Explain why?

What is a salt?

Give the names and formulae of any two salts. Also name the acids and bases from which these salts may be obtained.

What is meant by ‘a family of salts’? Explain with examples.

What is meant by ‘hydrated’ salts? Explain with examples.

What is meant by ‘anhydrous’ salts? Explain with examples.

Write the names, formulae and colours of any two hydrated salts.

What will be the colour of litmus in an aqueous solution of ammonium chloride salt?

The salt which will give an acidic solution on dissolving in water is ______.

One of the following salts will give an alkaline solution on dissolving in water. This is:

The salt which will give a neutral solution on dissolving in water will be ______.

The products of chloro-alkali process are ______.

The number of molecules of water of crystallisation present in washing soda crystals is ______.

The salt whose aqueous solution will turn blue litmus to red is ______.

The aqueous solution of one of the following salts will turn red litmus to blue. This salt is:

The salt whose aqueous solution will have no effect on either red litmus or blue litmus is ______.

The aqueous solution of one of the following salts will turn phenolphthalein indicator pink. This salt is:

The formula of baking soda is ______.

Which of the following is treated with chlorine to obtain bleaching powder?

Plaster of Paris is prepared by heating one of the following to a temperature of 100°C. This is:

A salt whose aqueous solution will have a pH of more than 7 will be ______.

A salt is dissolved in water and the pH of this salt solution is measured with a universal indicator paper. If the pH of solution is less than 7, the salt is most likely to be ______.

Which of the following salts will give an aqueous solution having pH of almost 7?

P and Q are aqueous solutions of sodium chloride and sodium hydroxide, respectively. Which of these will turn:

1. blue litmus red?
2. red litmus blue?

The metal salt A is blue in colour. When salt A is heated strongly over a burner, then a substance B is eliminated and a white powder C is left behind. When a few drops of a liquid D are added to powder C, it becomes blue again. What could be A, B, C and D?

When the concentrated aqueous solution of substance X is electrolysed, then NaOH, Cl₂ and H₂ are produced. Name the substance X. What is the special name of this process?

Consider the following substances:

NaCl, Ca(OH)₂, NaHCO₃, NH₃, Na₂CO₃, H₂O, Cl₂, CO₂, CaSO₄.2H₂O, 2CaSO₄.H2O, CaOCl₂

1. Which two substances combine to form bleaching powder?
2. Which four substances are utilised in the production of washing soda?
3. Which compound represents plaster of Paris?
4. Which compound is a part of baking powder?
5. Which compound is used as an antacid?

Give one example of a salt which gives an aqueous solution having:

pH less than 7

Give one example of a salt which gives an aqueous solution having:

pH equal to 7

Give one example of a salt which gives an aqueous solution having:

pH more than 7

A compound X which is prepared from gypsum has the property of hardening when mixed with a proper quantity of water.

1. Identify the compound X.
2. Write the chemical equation for its preparation.
3. For what purpose is it used in hospitals?

Consider the following salts:

Na₂CO₃, NaCl, NH₄Cl, CH₃COONa, K₂SO₄, (NH)₂SO₄

Which of these salts will give:

1. acidic solutions?
2. neutral solutions?
3. basic solutions (or alkaline solutions)?

Write the name and formula of one salt which contains:

Two molecules of water of crystallisation.

Write the name and formula of one salt which contains:

Five molecules of water of crystallisation

Write the name and formula of one salt which contains:

Ten molecules of water of crystallisation.

How many molecules of water of crystallisation (per formula unit) are present in:

Copper sulphate crystals

How many molecules of water of crystallisation (per formula unit) are present in:

Washing soda

How many molecules of water of crystallisation (per formula unit) are present in:

Gypsum