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ChemistryClass 10ICSE

What happens when silver chloride is exposed to sunlight? Write a chemical equation for this reaction. Also give one use of such a reaction.

When silver chloride is exposed to light, it decomposes to form silver metal and chlorine gas which is a photolytic decomposition reaction,decomposition carried out by sunlight. 2AgCl(s) → 2Ag(s) + Cl2 This reaction is used in black and white photography.

ChemistryClass 10ICSE

What happens when silver nitrate solution is added to sodium chloride solution? (a) Write the equation for the reaction which takes place. Name the type of reaction involved.

When silver nitrate solution is added to sodium chloride solution, a white precipitate of silver chloride is formed alongwith sodium nitrate solution. AgNO3 (aq) + NaCl (aq) → AgCl (s)+ NaNO3 (aq) Double displacement reaction that is a chemical reaction where two compounds react and the positive ions and negative ions of the two reactants switch places forming new compounds.

ChemistryClass 10ICSE

In the reaction represented by the following equation: (a) Name the substance oxidised (b) Name the substance reduced (c) Name the oxidising agent Name the reducing agent

H2 (Addition of oxygen dihydrogen) CuO (Removal of oxygen) CuO (Beingreduced) H2(Being oxidized)

ChemistryClass 10ICSE

What happens when a piece of iron metal is placed in copper sulphate solution? Name the type of reaction involved. (b) Write balanced chemical equation with state symbols for the following reaction: Barium chloride solution reacts with sodium sulphate solution to give insoluble barium sulphate and a solution of sodium chloride.

(a) When a piece of iron metal is placed in copper sulphate solution, then magnesium sulphate solution and copper metal are formed. This is a type of displacement reaction. CuSO4 + Fe → FeSO4 + Cu (b) Na2SO4 + BaCl2 → BaSO4 + 2NaCl

ChemistryClass 10ICSE

Why are decomposition reactions called the opposite of combination reactions? Explain with equations of these reactions. (b) Express the following facts in the form of a balanced chemical equation: "When a strip of copper metal is placed in a solution of silver nitrate, metallic silver is precipitated and a solution containing copper nitrate is formed."

The reactions those split or break the compounds into two simpler products are called decomposition reaction Example: decomposition of calcium carbonate into calcium oxide and carbon dioxide when heated CaCO3→ CaO + CO2 They are called opposite of combination reaction because in combination reaction two or more reactants combined to form one single product Example Magnesium and oxygen combine to form magnesium dioxide 2Mg + O2→ 2MgO (b) Cu (s) + 2AgNO3 (aq)→ Cu(NO3)2 (aq) + 2Ag (s)

ChemistryClass 10ICSE

What is meant by (a) displacement reaction, and (b) double displacement reaction? Explain with the help of one example each.

Displacement reaction is a reaction in which one active element displaces a less reactive element from its salt solution 2KI + Cl2 → 2KCl + I2 Double displacement reaction is a chemical change in which two ionic compounds are exchanged and make components Fe2O3 + 6HCl → 2FeCl3 + 3H2O

ChemistryClass 10ICSE

Define the following in terms of gain or loss of hydrogen with one example each: (i) Oxidation (ii) reduction (b) When a magnesium ribbon is heated, it burns in air to form magnesium oxide. Write a balanced chemical equation for this reaction. Name (i) substance oxidised, and (ii) substance reduced.

Oxidation is removal of hydrogen and reduction is gaining of hydrogen. By taking an example Fe2O3 + 3CO → 2Fe + 3CO2 Fe got reduced here and Carbon got oxidized by gaining oxygen (b) 2Mg + O2→ 2MgO (i) Substance oxidized is Mg (ii) Substance reduced is O2

ChemistryClass 10ICSE

Explain the following in terms of gain or loss of Oxygen with one example each: (i) Oxidation (ii) reduction (b) When copper powder is heated strongly in air, it forms copper oxide. Write a balanced chemical equation for this reaction. Name (i) substance oxidised, and (ii) substance reduced

(a) Oxidation is addition of oxygen and reduction is removing of oxygen H2S + Cl2→ S + 2HCl Here, hydrogen is removed from hydrogen sulphide so it is oxidation and hydrogen sulphide is oxidized to sulphur. (b) 2Cu + O2 → 2Cu0 (i) Cu is oxidized (ii) O2is reduced

ChemistryClass 10ICSE

Give one example of an oxidation-reduction reaction which is also: (a) A combination reaction A displacement reaction

2Cu + O2 → 2CuO (Heat is given) Copper combines with oxygen to form copper oxide and it is a oxidation-reduction reaction CuO + H2→ Cu + H2O Here hydrogen displaces copper to form dihydrogen oxide (Water)

ChemistryClass 10ICSE

Zinc oxide reacts with carbon, on heating, to form zinc metal and carbon monoxide. Write a balanced chemical equation for this reaction. Name (i) oxidizing agent, and (ii) reducing agent, in this reaction.

ZnO + C → Zn + CO Oxidizing agents is a reactant which gain electrons and reduced during a redox reaction and here Zinc oxide is the oxidizing agent Reducing agent or reductant is that which substance causes another substance to reduce or it loses electron and oxidized in a chemical reaction. Here carbon is reducing agent.

ChemistryClass 10ICSE

What is a decomposition reaction? Give an example of a decomposition reaction. Describe an activity to illustrate such a reaction by heating.

Decomposition reaction is a reaction where the compounds break down or splits into two or more products. They are classified into three. Thermal decomposition, electrolytic decomposition and photo decomposition reaction There are so many examples for decomposition reactions one of them is decomposition of calcium carbonate into calcium oxide and carbon dioxide when heated Decomposition reaction by heating is called Thermal decomposition reaction. Here is an example for that kind of reaction 2KClO3(s) + Heat → 2KCl + 3O2 Potassium chromate decomposes into potassium chloride and oxygen gas is evolved.

ChemistryClass 10ICSE

What is the colour of ferrous sulphate crystals? How does this colour change after heating? (b) Name the product formed on strongly heating ferrous sulphate crystals. What type of chemical reaction occurs in this change?

Ferrous sulphate crystals are green in colour and after heating it becomes white because on heating ferrous sulphate crystals loses water and anhydrous ferrous sulphate FeSO4 is formed so the colour changes from light green to white. (b) On strong heating the anhydrous sulphate decomposes to form Ferric oxide, sulphur dioxide and sulphur trioxide. This is a decomposition reaction 2FeSO4→ Fe2O3 + SO2+ SO3

ChemistryClass 10ICSE

Give an example of an endothermic reaction? (b) Is oxidation an exothermic or an endothermic reaction? Explain, by giving an example, how oxidation and reduction processed side by side.

Endothermic reaction is a reaction heat is absorbed by the reaction and example is burning of carbon in presence of oxygen gives carbon dioxide and a large amount of heat is released C (s) + O2 (g) →CO2 + Heat Oxidation is an exothermic Oxidation is areaction which oxygen combines with other elements and exothermic reaction releases energy through light or heat CuO + H2→ Cu + H2O In this above reaction, Copper oxide is reduced to copper and hydrogen is oxidized to water

ChemistryClass 10ICSE

Define a combination reaction. (b) Give one example of a combination reaction which is also exothermic. Give one example of a combination reaction which is also endothermic.

Combination reactions are those reactions in which two or more substances combine to form a single substance or product or two reactants combine to form one product C (s) + O2 (g) →CO2 + Heat (Burning of carbon in presence of oxygen to produce carbon dioxide) N2 (g) + O2 (g) + Heat → 2NO (g)

ChemistryClass 10ICSE

What is a redox reaction? Explain with an example. (b) When a magnesium ribbon burns in air with a dazzling flame and forms a white ash, is magnesium oxidised or reduced? Why? (c) In the reaction represented by the equation: MnO2 + 4HCl → MnCl2 +2H2O +Cl2 (i) Name the substance oxidized (ii) Name the oxidizing agent Name the substance reduced (iv) Name the reducing agent

A redox reaction is a reaction where oxidation and reduction occurs It is also called redox reaction. SO3(aq) + MnO4(aq) → SO4(aq) + Mn Oxidation happened for SO3and reduction happened for MnO4 Magnesium is oxidised as addition of oxygen to magnesium takes place leading to formation of magnesium oxide. (i) HCl (ii) MnO2(iii) MnO2 (iv) HCl

ChemistryClass 10ICSE

What is an oxidation reaction? Identify in the following reaction (i) the substance oxidized, and (ii) substance reduced: ZnO + C → Zn +CO

Oxidation is the process when an atom loses its electron in a reaction. Or the addition of oxygen to a substance to increase the proportion of oxygen in its molecule and oxidation can be achieved without oxygen by the removal of hydrogen i.e. dehydrogenation. (i)Substance oxidized is C (ii) Substance reduced is ZnO

ChemistryClass 10ICSE

Fill in the following blanks with suitable words: (a) The addition of oxygen to a substance is called whereas removal of oxygen is called . (b) The addition of hydrogen to a substance is called whereas removal of hydrogen is called . Anti-oxidants are often added to fat containing foods to prevent due to oxidation

Solution: Oxidation; Reduction;

ChemistryClass 10ICSE

When SO2 gas is passed through saturated solution of H2S, the following reaction occurs: SO2 + 2H2S → 2H2O +3S In this reaction, which substance is oxidized and which one is reduced?

In this reaction the substance oxidised is H2S and the substance which got reduced is SO2

ChemistryClass 10ICSE

Identify the component oxidized in the following reaction: H2S +Cl2→ S +2HCl

H2S is oxidized in the above reaction.

ChemistryClass 10ICSE

In the following reaction between lead sulphide and hydrogen peroxide: PbS(s) + 4H2O2(aq) → PbSO4(s) +4H2O(l) (a) Which substance is reduced? Which substance is oxidized?

H2O2 PbS

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