(a) (i) The reactants are copper oxide and hydrogen. Copper oxide undergoes reaction and hydrogen (H₂) undergoe oxidation.
(ii) The reactants are copper oxide and zinc. Zinc undergoes oxidation and copper oxide undergoes reduction.
(b) Calcium carbonate is reduced in industries to get CaO and CO₂.

(a) (i) No change in color.
(ii) Red litmus turns blue.
(b) (i) 2NaOH(aq)+FeSO₄(aq)\(\rightarrow\)Fe(OH)₂(s)+Na₂SO₄(aq)

Name of the Solution	Colour change with phenolphthalein	Colour change with blue litmus
1. Sodium carbonate	turns pink	no change
2. Hydrochloric acid	no change	turns red
3. Sodium chloride	no change	no change

(i) Increase in the strength of alkali. So the nature of solution will be basic.
(ii) Hydroxide ion or hydroxyl ion or OH^- ion.
(iii) A paper impregnated with the universal indicator is generally used to measure the pH of a solution.

(i) H₂ + Cl₂ \(\rightarrow\) 2HCI
(ii) 3BaCl₂ + Al₂(SO₄)₃ \(\rightarrow\) 3BaSO₄ \(\downarrow\)+ 2AlCl₃
(iii) 2Na + 2H₂O \(\rightarrow\) 2NaOH + H₂

 

ZnO(s) and CO₂(g) are formed.
Chemical Equation:
ZnCO₃ → ZnO + CO₂

Quick lime reacts with water vigorously to produce slaked lime and a large amount of heat.
\(\underset { (Quick\quad lime) }{ CaO(s) } +{ H }_{ 2 }O\rightarrow \underset { (Slaked\quad lime) }{ Ca(O{ H) }_{ 2 } } +Heat\)

In a physical change, no new substance is formed. In a chemical change, new substance is formed.

Formic acid(Methanoic acid) HCOOH.

X - NaOH (Sodium hydroxide)
A - Na₂ZnO₂ (Sodium zincate)
B - NaCI (Sodium chloride)
C - CH₃COONa (Sodium acetate)

Oxidation the reaction seen during rancidity of food.

It is a double displacement reaction.

An example of photochemical reactions is the process of photosynthesis occurring in the leaves of green plants.
\(\underset { Carbon\\ dioxide }{ { 6CO }_{ 2 } } +\underset { Water}{ { 6H }_{ 2 } O} \overset { sunlight }{ \underset { Chlorophyll }{ \rightleftharpoons } } \underset {Glucose }{ C_6H_{12}O_6 } +\underset {Oxygen }{6{ O }_{ 2 }}\)

A catalyst changes the rate of reaction without taking part in the reaction itself.

i. Neutralization reaction
ii. Oxidation reaction

A solution of ammonia in water results in the formation of ammonium hydroxide (NH₄OH).  Ammonium hydroxide is basic in nature and turns red litmus blue.

pH	Liquid
7.0	Distilled Water
14.0	1 M sodium hydroxide solution
4.0	Tomato juice
2.0	Lemon juice

(a) Pb₃O₄ 
(b) O₂
(c) CuSO₄
(d) V₂O₅
(e) H₂O
(f) CuO

(a) NH₃
(b) F₂
(c) CO
(d) H₂

(a) - (ii);  (b) - (iii);  (c) - (iv); (d) - (i)

A substance 'A' which displaces 'B' from its solution in water must be higher in reactivity. Therefore, 'A' must be high reactivity metal, let us say zinc(Zn). The 'B' must be copper sulphate solution. This is because copper is least reactive than zinc.
CuSO₄+Zn\(\rightarrow\)ZnSO₄+Cu
In this reaction, zinc is oxidised to zinc sulphate and copper sulphate is reduced to copper metal. Thus this reaction is also called redox reaction.

The yellowish compound is silver bromide [AgBr].
When silver bromide is exposed to sun light, it produces a grey coloured silver metal.
\(2AgBr\longrightarrow2Ag+Br_2\)
Thus 'A' is silver bromide [AgBr], 'B' is silver metal [Ag] and 'C' is bromine [Br₂]
The nitrate of 'B' is silver nitrate [AgNO3]
Silver nitrate when treated with sodium bromide, it forms silver bromide.
AgNO₃+NaBr\(\rightarrow\)AgBr+NaNO₃

(a) 2HNO₃   +   Ca(OH)₂            \(\rightarrow\) Ca(NO₃)₂          + 2H₂O
Nitric acid      Calcium hydroxide     Calcium nitrate     Water
(b) 2NaOH          + H₂SO₄             \(\rightarrow\) Na₂SO₄           +    2H₂O
Sodium hydroxide  Sulphuric acid     Sodium sulphate   Water
(c) NaCl            +    AgNO₃         \(\rightarrow\)  AgCl            +  NaNO₃
Sodium chloride    Silver nitrate      Silver chloride    Sodium nitrate
(d) BaCl₂          + H₂SO₄             \(\rightarrow\) BaSO₄              + 2HCl
Barium chloride    Sulphuric acid     Barium sulphate   Hydrochloric acid

(i) Substance X is calcium oxide or quicklime. Its formula is CaO
(ii) Quicklime reacts with water as:
CaO(s) + H₂O(l) \(\rightarrow\)Ca(OH)₂ (aq)
    X          Water       Slaked lime (Calcium hydroxide)

(i) BaCl₂(aq) + Na₂SO₄ (aq) \(\rightarrow\) BaSO₄(s)\(\downarrow\) + 2NaCl(aq)
(ii) NaOH (aq) + HCl (aq) \(\rightarrow\) NaCl (aq) + H₂O(l)

(a) Concentrated sulphuric acid is called the king of chemicals as it is a very strong acid and is highly corrosive.

(b) The three chemical reactions that take place during the conversion of sulfur dioxide to sulphuric acid in the 'Contact Process' are given below.

Step I: Sulphur dioxide is mixed with air and passed over vanadiumpent (V) oxide catalyst heated to \(450^oC\) to form sulphur trioxide.

\(\underset{Sulphur\ dioxide}{2SO_{2(g)}}+\underset{Oxygen}{O_{2(g)}}\underset{\rightleftharpoons }{V_2O_5}\underset{Sulphur\ trioxide}{2SO_{3(g)}}+Heat\)

Step II : Sulphur trioxide is dissolved in concentrated sulphuric acid to form a thick fuming liquid called oleum.

\(\underset{Sulphuric\ acid}{H_2SO_4(l)}+\underset{Sulphur\ trioxide}{SO_{3(g)}}\begin{matrix} V_2O_5 \\ \rightleftharpoons \\ \end{matrix}\underset{Oleum}{H_2S_2O_{7(l)}}\)

Step III: Oleum is diluted with a calculated quantity of water to obtain sulphuric acid.

\(H_2S_2O_{7(l)}+\underset{Water}{H_2O_{(l)}}\rightarrow\underset{Sulphuric\ acid}{2H_2SO_{4(aq)}}\)

(c) If water is added to sulphuric acid then a large amount of heat is evolved.  This changes water to steam, which can splash the acid.  Hence, it is dangerous.