NCERT Exemplar solutions for Science [English] Class 10 chapter 1 - Chemical Reactions and Equations [Latest edition]

Which of the following is not a physical change?

The following reaction is an example of a `4"NH"_3("g") + "SO"_2 -> 4"NO"("g") + 6"H"_2"O"("g")`

1. displacement reaction
2. combination reaction
3.  redox reaction
4. neutralisation reaction

Which of the following statements about the given reaction are correct?

`3"Fe"("s") + 4"H"_2"O"("g") -> "Fe"_3"O"_4("s") + 4"H"_2("g")`

1.  Iron metal is getting oxidised
2. Water is getting reduced
3. Water is acting as reducing agent
4.  Water is acting as oxidising agent

Which of the following are exothermic processes?

1. Reaction of water with quick lime
2. Dilution of an acid
3. Evaporation of water
4.  Sublimation of camphor (crystals)

Three beakers labelled as A, B and C each containing 25 mL of water were taken. A small amount of NaOH, anhydrous CuSO₄ and NaCl were added to the beakers A, B and C respectively. It was observed that there was an increase in the temperature of the solutions contained in beakers A and B, whereas in case of beaker C, the temperature of the solution falls. Which one of the following statement(s) is(are) correct?

1.  In beakers A and B, exothermic process has occurred.
2. In beakers A and B, endothermic process has occurred.
3. In beaker C exothermic process has occurred.
4.  In beaker C endothermic process has occurred.

A dilute ferrous sulphate solution is gradually added to the beaker containing acidified permanganate solution. The light purple colour of the solution fades and finally disappears. Which of the following is the correct explanation for the observation?

Which among the following is(are) double displacement reaction(s)?

1. `"Pb" + "CuCl"_2 -> "PbCl"_2 + "Cu"`
2. `"Na"_2"SO"_4 + "BaCl"_2 -> "BaSO"_4 + 2"NaCl"`
3. `"C" + "O"_2 -> "CO"_2`
4. `"CH"_4 + 2"O"_2 -> "CO"_2 + 2"H"_2"O"`

Which among the following statement(s) is(are) true? ‘Exposure of silver chloride to sunlight for a long duration turns grey due to

1.  the formation of silver by decomposition of silver chloride
2.  sublimation of silver chloride
3. decomposition of chlorine gas from silver chloride
4. oxidation of silver chloride

Solid calcium oxide reacts vigorously with water to form calcium hydroxide accompanied by liberation of heat. This process is called slaking of lime. Calcium hydroxide dissolves in water to form a solution called lime water. Which among the following is (are) true about slaking of lime and the solution formed?

1.  It is an endothermic reaction
2.  It is an exothermic reaction
3. The pH of the resulting solution will be more than seven
4. The pH of the resulting solution will be less than seven

Barium chloride on reacting with ammonium sulphate forms barium sulphate and ammonium chloride. Which of the following correctly represents the type of the reaction involved?

1. Displacement reaction
2. Precipitation reaction
3. Combination reaction
4. Double displacement reaction

Electrolysis of water is a decomposition reaction. The mole ratio of hydrogen and oxygen gases liberated during electrolysis of water is

Which of the following is(are) an endothermic process(es)?

1. Dilution of sulphuric acid
2. Sublimation of dry ice
3. Condensation of water vapours
4. Evaporation of water

In the double displacement reaction between aqueous potassium iodide .and aqueous lead nitrate, a yellow precipitate of lead iodide is formed. While performing the activity if lead nitrate is not available, which of the following can be used in place of lead nitrate?

Which of the following gases can be used for storage of fresh sample of an oil for a long time?

The following reaction is used for the preparation of oxygen gas in the laboratory

`2"KClO"_3("s") overset("Heat")underset("Catalyst")(->) 2"KCl"("s") + 3"O"_2 ("g")`

Which of the following statement(s) is(are) correct about the reaction ?

Which one of the following processes involve chemical reactions?

In which of the following chemical equations, the abbreviations represent the correct states of the reactants and products involved at reaction temperature?

Which of the following are combination reactions?

1. `2"KClO"_3 overset("Heat")(->) 2"KCl" + 3"O"_2`
2. `"MgO" + "H"_2"O" -> "Mg"("OH")_2`
3. `4"Al" + 3"O"_2 -> 2"Al"_2"O"_3`
4. `"Zn" + "FeSO"_4 -> "ZnSO"_4 + "Fe"`

Write the balanced chemical equations for the following reactions and identify the type of reaction in each case.

1. Nitrogen gas is treated with hydrogen gas in the presence of a catalyst at 773 K to form ammonia gas.
2. Potassium hydroxide solution is treated with acetic acid to form potassium acetate and water.
3. Ethanol is warmed with ethanoic acid to form ethyl acetate in the presence of concentrated H₂SO₄.
4. Ethene is burnt in the presence of oxygen to form carbon dioxide, water and release heat and light. 

Write the balanced chemical equations for the following reactions and identify the type of reaction in each case.

1. Iron (III) oxide reacts with aluminum and gives molten iron and aluminum oxide.
2. Magnesium ribbon is burnt in an atmosphere of nitrogen gas to form solid magnesium nitride.
3. Chlorine gas is passed in an aqueous potassium iodide solution to form potassium chloride solution and solid iodine.
4. Ethanol is burnt in air to form carbon dioxide, water and releases heat. 

Complete the missing component /variable given as x and y in the following reactions :

`"Pb"("NO"_3)_2("aq") + 2"Kl"("aq") -> "Pbl"_2(x) + 2"KNO"_3("y")`

Complete the missing component /variable given as x and y in the following reactions

`"Cu"("s") + 2"AgNO"_3("aq") -> "Cu"("NO"_3)_2("aq") + x("s")`

Complete the missing component /variable  given as x and y in the following reactions

`"Zn"("s") + "H"_2"SO"_4("aq") -> "ZnSO"_4(x) + "H"_2("y")`

Complete the missing component/variable given as x and y in the following reactions

`"CaCO"_2(s)overset(x)(->) "CaO"("s") + "CO"_2("g")`

Which among the following change is exothermic or endothermic in nature?

Decomposition of ferrous sulphate

Which among the following change is exothermic or endothermic in nature?

Dilution of sulphuric acid

Which among the following change is exothermic or endothermic in nature?

Dissolution of sodium hydroxide in water

Which among the following change is exothermic or endothermic in nature?

Dissolution of ammonium chloride in water

Identify the reducing agent in the following reactions

`4"NH"_3 + 5"O"_2 -> 4"NO" + 6"H"_2"O"`

Identify the reducing agent in the following reactions - 

`"H"_2"O" + "F"_2 -> "HF" + "HOF"`

Identify the reducing agent in the following reactions

`"Fe"_2"O"_3 + 3"CO" -> 2"Fe" + 3"CO"_2`

Identify the reducing agent in the following reactions

`2"H"_2 + "O"_2 -> 2"H"_2"O"`

Identify the oxidising agent (oxidant) in the following reactions 

`"Pb"_3"O"_4 + 8"HCl" -> 3"PbCl"_2 + "Cl"_2 + 4"H"_2"O"`

Identify the oxidising agent (oxidant) in the following reactions

`2"Mg" + "O"_2 -> 2"MgO"`

Identify the oxidising agent (oxidant) in the following reactions

`"CuSO"_4 + "Zn" -> "Cu" + "ZnSO"_4`

Identify the oxidising agent (oxidant) in the following reactions

`"V"_2"O"_5 + 5"Ca" -> 2"V" + 5"CaO"`

Identify the oxidising agent (oxidant) in the following reactions

`3"Fe" + 4"H"_2"O" -> "Fe"_3"O"_4 + 4"H"_2`

Identify the oxidising agent (oxidant) in the following reactions.

`"CuO" + "H"_2 -> "Cu" + "H"_2"O"`

Write the balanced chemical equation for the following reaction

Sodium carbonate on reaction with hydrochloric acid in equal molar concentrations gives sodium chloride and sodium hydrogencarbonate.

Write the balanced chemical equation for the following reaction

Sodium hydrogencarbonate on reaction with hydrochloric acid gives sodium chloride, water and liberates carbon dioxide.

Write the balanced chemical equation for the following reaction

Copper sulphate on treatment with potassium iodide precipitates cuprous iodide (Cu₂I₂), liberates iodine gas and also forms potassium sulphate.

A solution of potassium chloride when mixed with silver nitrate solution, an insoluble substance is formed. Write the chemical reaction involved and mention the type of the chemical reaction.

Ferrous sulphate decomposes with the evolution of a gas having a characteristic smell of burning sulphur. Write the chemical reaction involved and identify the type of reaction.

Why do fire flies glow at night ?

Grapes hanging on the plant do not ferment but after being plucked from the plant can be fermented. Under what conditions do these grapes ferment? Is it a chemical or a physical change?

Which among the following are physical or chemical change?

 Evaporation of petrol

Which among the following are physical or chemical change?

Burning of Liquefied Petroleum Gas (LPG)

Which among the following are physical or chemical change?

Heating of an iron rod to red hot

Which among the following are physical or chemical change?

Curding of milk

Which among the following are physical or chemical change?

Sublimation of solid ammonium chloride

During the reaction of some metals with dilute hydrochloric acid, following observations are made.

Silver metal does not show any change

Explain this observation giving suitable reason.

During the reaction of some metals with dilute hydrochloric acid, following observations are made.

The temperature of the reaction mixture rises when aluminium (Al) is added.

Explain this observation giving suitable reason.

During the reaction of some metals with dilute hydrochloric acid, following observations are made.

The reaction of sodium metal is found to be highly explosive

Explain this observation giving suitable reason.

During the reaction of some metals with dilute hydrochloric acid, following observations are made.

The reaction of sodium metal is found to be highly explosive

Explain this observation giving suitable reason.

During the reaction of some metals with dilute hydrochloric acid, following observations are made.

Some bubbles of a gas are seen when lead (Pb) is reacted with the acid.

A substance X, which is an oxide of a group 2 element, is used intensively in the cement industry. This element is present in bones also. On treatment with water it forms a solution which turns red litmus blue. Identify X and also write the chemical reactions involved.

Write a balanced chemical equation of the following reaction and also classify them.

Lead acetate solution is treated with dilute hydrochloric acid to form lead chloride and acetic acid solution.

Write a balanced chemical equation of the following reaction and also classify them.

A piece of sodium metal is added to absolute ethanol to form sodium ethoxide and hydrogen gas.

Write a balanced chemical equation of the following reaction and also classify them.

 Iron (III) oxide on heating with carbon monoxide gas reacts to form solid iron and liberates carbon dioxide gas.

Write a balanced chemical equation of the following reaction and also classify them.

Hydrogen sulphide gas reacts with oxygen gas to form solid sulphur and liquid water.

Why do we store silver chloride in a dark coloured bottle?

Balance the following chemical equation and identify the type of chemical reaction.

`"Mg"("s") + "Cl"_2("g") -> "MgCl"_2("s")`

Balance the following chemical equation and identify the type of chemical reaction.

`"HgO"("s") overset("(heat)")(->) "Hg"("l") + "O"_2("g")`

Balance the following chemical equation and identify the type of chemical reaction.

`"Na"("s") + "S"("s") overset("(Fuse)")(->) "Na"_2"S"("s")` 

Balance the following chemical equation and identify the type of chemical reaction.

`"TiCl"_4("l") + "Mg"("s") -> "Ti"("s") + "MgCl"_2("s")`

Balance the following chemical equation and identify the type of chemical reaction.

`"CaO"("s") + "SiO"_2("s") -> "CaSio"_3("s")`

Balance the following chemical equation and identify the type of chemical reaction.

`"H"_2"O"_2("l") overset("U  V")(->) "H"_2"O"("l") + "O"_2("g")`

A magnesium ribbon is burnt in oxygen to give a white compound ‘X’ accompanied by emission of light. If the burning ribbon is now placed in an atmosphere of nitrogen, it continues to burn and forms a compound ‘Y’.

1. Write the chemical formulae of X and Y.
2. Write a balanced chemical equations when X and Y are dissolved in water.

Zinc liberates hydrogen gas when reacted with dilute hydrochloric acid whereas copper does not. Explain why?

A silver article generally turns black when kept in the open for a few days. The article when rubbed with toothpaste again starts shining.

1.  Why do silver articles turn black when kept in the open for a few days? Name the phenomenon involved.
2. Name the black substance formed and give its chemical formula.

On heating blue coloured powder of copper (II) nitrate, in a boiling tube, copper oxide (black), oxygen gas and a brown gas X is formed

1. Write a balanced chemical equation of the reaction.
2. Identify the brown gas X evolved.
3.  Identify the type of reaction.
4. What could be the pH range of aqueous solution of the gas X?

Give the characteristic tests for the following gases :

1. CO₂
2. SO₂
3. O₂
4. H₂

What happens when a piece of

1. zinc metal is added to copper sulphate solution?
2. aluminium metal is added to dilute hydrochloric acid?
3.  silver metal is added to copper sulphate solution?

Also write the balanced chemical equation if the reaction occurs.

What happens when zinc granules are treated with dilute solution of H₂SO₄, HCl, HNO₃, NaCl and NaOH Also write the chemical equations if reaction oçcurs.

On adding a drop of barium chloride solution to an aqueous solution of sodium sulphite, white precipitate is obtained :

1. Write a balanced chemical equation for the reaction involved.
2. What other name can be given to this precipitation reaction?
3. On adding dilute hydrochloric acid to the reaction mixture, white precipitate disappears. Why?

You are provided with two containers made up of copper and aluminium. You are also provided with solutions of dilute HCl, dilute HNO₃, ZnCl₂ and water. In which of the above containers, can these solutions be kept?