What causes rancidity? Name an antioxidant which prevents rancidity.

Balance the equation: S + HNO₃→ H₂SO₄ + NO₂ + H₂O

In electrolysis of water, why is the volume of gas collected over one electrode double that of gas collected over the other electrode?

Why respiration and decomposition processes are considered to be an exothermic process?

Identify the substance oxidised and reduced in the chemical reaction:

2Mg + O₂→ 2MgO

Why potato chips manufacturers fill the packet of chips with nitrogen gas?

Identify the type of reaction:

Fe + CuSO₄(aq) → FeSO₄(aq) + Cu(s)

Balance the given chemical equation:

Al(s) + CuCl₂(aq) → AlCl₃(aq) + Cu(s)

What happens chemically when quicklime is added to water?

On adding dilute HCl to CuO powder, the solution formed is blue green. Predict the new compound formed which imparts a blue-green colour to the solution.

What happens when:

(a) copper powder is heated in a china dish?

(b) hydrogen gas is passed over hot copper (II) oxide?

A student has found black coating on his silver coins and green coating on his copper coins. Which chemical phenomenon is responsible for this? Write chemical name of these coatings.

Give differences between Oxidation and Reduction.

How combination reaction differs from decomposition reaction?

Differentiate between displacement and double displacement reactions.

What is observed when:

(i) Potassium iodide is added to aqueous lead nitrate?

(ii) Identify the type of reaction.

(iii) Give a balanced chemical equation for this.

Define oxidising and reducing agents by giving suitable example.

What is meant by rancidity? How it can be prevented?

Give reason why:

(a) Magnesium ribbon should be cleaned before burning at air.

(b) Iron should be protected from moist air.

What happens when:

(i) Lead nitrate is heated

(ii) crystals of FeSO₄ are heated?

Give two examples each of:

Double displacement reactions.

Give two examples each of:

Redox reactions

Give two examples each of:

Combination reactions.

Differentiate between exothermic and endothermic reactions by giving one example of each. [3 marks]

Give reason why:

Na acts as a reducing agent while chlorine acts as an oxidising agent in reaction:

2Na(s) + Cl₂(g) → 2NaCl(s)

Give reason why:

White coloured AgCl turns grey when kept in sunlight.

Give reason why:

Colour of the solution changes when iron nail is dipped in copper sulphate solution.

Give reason why:

Lime water turns milky when CO₃ is passed through it?

Calcium oxide reacts vigorously with water to produce:

The reaction, 3MnO₂(s) + 4Al(s) → 3Mn(ℓ) + 2Al₂O₅(s) + Heat is

an example of:

Which is the reducing agent in the following reaction?

MnO₂(s) + 4HCl (aq) → MnCl₂(s) + 2H₂O(ℓ) + Cl₂(ℓ)

Which is the oxidizing agent in the following reaction?

CuO(s) + H₂(g) → Cu(s) + H₂O(ℓ)

The coating formed on the metals such as iron, silver and copper after corrosion will be:

The changes which take place when fats and oils are oxidised:

The substances which get oxidised easily can be kept for longer duration by:

The colour formed on the surface of copper powder when it is heated in a china dish:

What happens when hydrogen gas is passed over the heated copper oxide (CuO)?

The reaction which is used in black and white photograph is:

The following reaction is an example of a:

4NH₃(g) + 5O₂(g) → 4NO(g) + 6H₂O(g)

(i) displacement reaction

(ii) combination reaction

(iii) redox reaction

(iv) neutralization reaction

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

3Fe(s) + 4H₂O(g) → Fe₃O₄(s) + 4H₂(g)

(i) Iron metal is getting oxidised

(ii) Water is getting reduced

(iii) Water is acting as reducing agent

(iv) Water is acting as oxidizing agent

Which of the following are exothermic processes?

(i) Reaction of water with quicklime

(ii) Dilution of an acid

(iii) Evaporation of water

(iv) Sublimation of camphor (crystals)

A dilute ferrous sulphate solution was 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)?

(i) Pb + CuCl₂→ PbCl₂ + Cu

(ii) Na₂SO₄ + BaCl₂→ BaSO₄ + 2NaCl

(iii) C + O₂→ CO₂

(iv) CH₄ + 2O₂→ CO₂ + 2H₂O

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

(i) The formation of silver by decomposition of silver chloride

(ii) Sublimation of silver chloride

(iii) Decomposition of chlorine gas from silver chloride

(iv) Oxidation of silver chloride

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

(i) Dilution of sulphuric acid

(ii) Sublimation of dry ice

(iii) Condensation of water vapours

(iv) 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?

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?

(i) 2KClO₃ 2KCl + 3O₂

(ii) MgO + H₂O → Mg(OH)₂

(iii) 4Al + 3O₂→ 2Al₂O₃

(iv) Zn + FeSO₄→ ZnSO₄ + Fe

Write true or false for the following statements:

On heating the crystals of ferrous sulphate, the colour changes from green to grey.

Write true or false for the following statements:

Calcium oxide is also called lime quicklime.

Write true or false for the following statements:

On heating the crystals of lead nitrate crystals, the emission of brown fumes occurs.

Write true or false for the following statements:

The thermal decomposition reaction of calcium sulphate (gypsum) is used in black and white photography.

Write true or false for the following statements:

The decomposition reaction of silver bromide into silver and bromine by light is used in the manufacturing of cement.

Write true or false for the following statements:

The insoluble substance formed during a chemical reaction is known as a precipitate.

Write true or false for the following statements:

During endothermic reactions, heat is transferred from the reacting substances to the surroundings.

Write true or false for the following statements:

The reaction Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s) is type of double displacement reaction

Write true or false for the following statements:

Keeping food in airtight containers helps to slow down oxidation.

Write true or false for the following statements:

Due to corrosion iron gets a brown coating, copper gets a green coating and silver gets a black coating.