Viraf J. Dalal solutions for New Simplified Middle School Chemistry [English] Class 8 chapter 6 - Chemical Reactions [Latest edition]

What is a chemical reaction?

A chemical reaction is often accompanied by external indications or characteristics which include – 

1. Colour change
2. Effervescence or gas evolved
3. Evolution or absorption of heat
4. Formation of a precipitate.

With reference to each of the above indications, state the external indication seen during – Addition of dilute acid to an active metal.

A chemical reaction is often accompanied by external indications or characteristics which include – 

1. Colour change
2. Effervescence or gas evolved
3. Evolution or absorption of heat
4. Formation of a precipitate.

With reference to each of the above indications, state the external indication seen during – Addition of dilute hydrochloric acid to silver nitrate.

A chemical reaction is often accompanied by external indications or characteristics which include – 

1. Colour change
2. Effervescence or gas evolved
3. Evolution or absorption of heat
4. Formation of a precipitate.

With reference to each of the above indications, state the external indication seen during – Addition of water to quicklime.

A chemical reaction is often accompanied by external indications or characteristics which include – 

1. Colour change
2. Effervescence or gas evolved
3. Evolution or absorption of heat
4. Formation of a precipitate.

With reference to each of the above indications, state the external indication seen during – Thermal decomposition of mercury [II] oxide.

State why a direct combination reaction is called a – ‘synthesis reaction’.

Differentiate between direct combination reaction and a decomposition reaction.

Differentiate between displacement reaction and a neutralization reaction.

Classify the following reaction into – 

1. Direct combination 
2. Decomposition
3. Displacement
4. Double decomposition

The reaction is – Zinc hydroxide on heating gives zinc oxide and water.

Classify the following reaction into – 

1. Direct combination 
2. Decomposition
3. Displacement
4. Double decomposition

The reaction is – Zinc reacts with copper [II] sulphate to give zinc sulphate and copper.

Classify the following reaction into – 

1. Direct combination 
2. Decomposition
3. Displacement
4. Double decomposition

The reaction is – Zinc sulphate reacts with ammonium hydroxide to give ammonium sulphate and zinc hydroxide.

Classify the following reaction into – 

1. Direct combination 
2. Decomposition
3. Displacement
4. Double decomposition

The reaction is – Molten zinc at high temperatures, burns in air to give zinc oxide.

Give a balanced equation for –

A direct combination reaction involving two elements, one of which is a non-metal

Give a balanced equation for –

A thermal decomposition reaction involving heat on limestone [calcium carbonate]

Give a balanced equation for –

An electrolytic decomposition reaction involving a neutral liquid

Give a balanced equation for –

A displacement reaction involving a metal above hydrogen in the activity series with copper [II] sulphate solution

Give a balanced equation for –

A double decomposition neutralization reaction involving an acid and a base

Give a balanced equation for –

A white precipitate obtained during a double decomposition reaction involving a silver salt with sodium salt.

State what is meant by the ‘reactivity series of metals’

With reference to Water explain with suitable examples of how the reactivity of the metals could be differentiated.

With reference to Acid explain with a suitable example of how the reactivity of the metals could be differentiated.

A chemical reaction may be ‘reversible’ in nature. State the meaning of the term in italics.

Give a reason why a catalyst is used in certain chemical reactions.

Give a balanced equation for the reversible catalytic reaction involving nitrogen as one of the reactants.

Give a balanced equation for the reversible catalytic reaction involving sulphur dioxide as one of the reactants.

State which type of chemical reaction proceeds with evolution of heat energy.

State which type of chemical reaction proceeds with the absorption of heat energy.

State the following reaction whether heat is evolved or absorbed – 

water is added to quicklime

State the following reaction whether heat is evolved or absorbed – 

Two neutral gases on passage through an electric are given nitric oxide.

State the following reaction whether heat is evolved or absorbed – 

Two neutral gases combine to give a basic gas.

Certain thermal decomposition reaction, resulting in the formation of the oxide. Give a balanced equation for the thermal decomposition of the following, which result in the formation of metallic oxide.

Limestone
\[\ce{CaCO3->[\Delta]CaO + CO2}\]

Certain thermal decomposition reaction, resulting in the formation of the oxide. Give a balanced equation for the thermal decomposition of the following, which result in the formation of metallic oxide.

Lead carbonate
\[\ce{PbCO3->[\Delta]PbO + CO2}\]

Certain thermal decomposition reaction, resulting in the formation of the oxide. Give a balanced equation for the thermal decomposition of the following, which result in the formation of metallic oxide.

Calcium nitrate
\[\ce{2Ca[NO3]2->[\Delta]2CaO + 4NO2 + O2}\]

Certain thermal decomposition reaction, resulting in the formation of the oxide. Give a balanced equation for the thermal decomposition of the following, which result in the formation of metallic oxide.

Calcium hydroxide
\[\ce{Ca[OH]2->[\Delta]CaO + H2O}\]

State the meaning of the term ‘oxide’.

Give a balanced equation for the formation of the following oxide –

Sulphur dioxide from a non-metal

Give a balanced equation for the formation of the following oxide –

Zinc oxide from a metal

Give a balanced equation for the formation of the following oxide –

Lead oxide from a mixed Oxide.

Give the example of the acidic oxide, basic oxide, amphoteric oxide and neutral oxide. State which of the oxide react with water to give a base.

Give the example of the acidic oxide, basic oxide, amphoteric oxide and neutral oxide. State which of the oxide react with a base to give salt and water.

Give the example of the acidic oxide, basic oxide, amphoteric oxide and neutral oxide. State which of the oxide react with acids and bases to give salt and water.

Give one example of –
A peroxide

Give one example of –
A mixed oxide

Give one example of –
A dioxide

Select the correct answer for the statement given below:

The product formed during direct combination reaction of carbon dioxide and water.

Select the correct answer for the statement given below:

The neutral gas obtained on thermal decomposition of potassium nitrate.

Select the correct answer for the statement given below:

The displaced product of the displacement reaction of sodium with cold water.

Select the correct answer for the statement given below:

The catalyst used in the catalytic reaction involving the reactants nitrogen and hydrogen.

Select the correct answer for the statement given below:

A neutral oxide which does not react with an acid or a base to give salt and water.

Complete the statement by filling in the blank with the correct word:

Direct combination reaction of phosphorus pentoxide with water gives _______.

Complete the statement by filling in the blank with the correct word:

Decomposition of silver salts in the presence of sunlight is an example of _________.

Complete the statement by filling in the blank with the correct word:

The element molybdenum used in the reaction of nitrogen with hydrogen at elevated temperatures is an example of a ________.

Complete the statement by filling in the blank with the correct word:

The reaction of coke with steam to give water gas is an example of an __________ reaction.

Complete the statement by filling in the blank with the correct word:

The metal which reacts with steam and the reaction is reversible is ________.

Give a balanced equation for the following type of reaction:

A thermal decomposition reaction in which a compound decomposes to give two new compounds.

Give a balanced equation for the following type of reaction:

A reaction of direct combination i.e. synthesis in which twp gases combine to give another gas – which turns lime water milky.

Give a balanced equation for the following type of reaction:

A thermal decomposition reaction in which a metallic nitrate decomposes to give – a basic oxide.

Give a balanced equation for the following type of reaction:

A catalytic, reversible, exothermic reaction.

Give a balanced equation for the following type of reaction:

A displacement reaction in which a metal above hydrogen in the reactivity series, displaces another metal from the solution of its compound.

Differentiate between the following:

Thermal decomposition and thermal dissociation.

Differentiate between the following:

Neutralization reaction and a precipitation reaction.

Differentiate between the following:

Electrolytic decomposition and photochemical decomposition.

Differentiate between the following:

A catalyst and a promoter.

Differentiate between the following:

An acidic oxide and a basic oxide.

Match the chemical reactions in List I with the appropriate answer in List II.