(i) The nature of the solution is acidic. It is a mixture of conc. HNO₃, and conc. HCI in the ratio of 1 : 3. It can dissolve gold as it is an oxidising agent.
(ii) Pure gold is 24 carat gold which is very soft.

(a) The main ore of aluminium is bauxite ore. Its formula is A1₂0₃.The impurities sociated with this ore are iron oxide and sand. .
(b) The reaction involved in obtaining pure alumina from mineral bauxite having impurities of iron oxide and silica are:
     (i) \(\underset { Aluminiumoxide\\ (frombauxiteore) }{ { A1 }_{ 2 }{ O }_{ 3 } } +\underset { Sodiumhydroxide\\ \quad (hot) }{ 2NaOH(aq) } \rightarrow \underset { Sodiumaluminate\\ \quad (Soluble) }{ { 2NaA1O }_{ 2 }(aq) } +\underset { Water }{ { H }_{ 2 }O(1) } \)
    The iron oxide and silica (sand) present in the bauxite ore do not dissolve in sodium hydroxide solution. Therefore, they are separated by filtration.
     (ii) \(\underset { Sodiumaluminate }{ { NaA1O }_{ 2 }(aq) } +\underset { Water }{ { 2H }_{ 2 }O(1) } \rightarrow \underset { Aluminiumhydroxide\\ \quad (Whiteppt) }{ { A1(OH) }_{ 3 }(s) } +\underset { Sodiumhydroxide }{ NaOH(aq) } \)
     (iii) \(\underset { Aluminiumhydroxide }{ { 2A1(OH) }_{ 3 }(s) } \underrightarrow { heat } \underset { Aluminiumoxide\\ \quad (Pure) }{ { A1 }_{ 2 }{ O }_{ 3 }(s) } +\underset { Steam }{ { 3H }_{ 2 }O(g) } \)

(a) The arrangement of metals in a vertical column in the order of decreasing reactivity is called the 'activity series' of metals. 
Following is the order of decreasing order of reactivity:
Cu> Fe> Zn> AI> Mg
(b) (i) When some zinc is put into blue copper sulphate solution, the blue colour of the copper sulphate solution fades gradually due to the formation of colourless zinc sulphate and red-brown copper metal is deposited on the zinc strip.
                           \(\underset { Coppersulphate\\ \quad (blue) }{ { CuSO }_{ 4 }(aq) } +\underset { Zinc }{ Zn } \rightarrow \underset { Zincsulphate\\ (Colourless) }{ { ZnSO }_{ 4 }(aq) } +\underset { \quad Copper\\ (Red-brown) }{ Cu(s) } \)
(ii) No reaction will take place since copper is less reactive than iron and hence will not displace it from ferrous sulphate solution.
(c) Sodium metal combines with hydrogen gas to form sodium hydride.
                           \(\underset { Sodiummetal }{ 2Na(s) } +\underset { Hydrogengas }{ { H }_{ 2 }(g) } \rightarrow \underset { Sodiumhydride }{ 2NaH(s) } \)

(a) The reaction involved in obtaining pure alumina from the mineral bauxite having impurities of iron oxide and silica is:
        (i) \(\underset { Aluminiumoxide\\ (frombauxiteore) }{ { AI }_{ 2 }{ O }_{ 3 }(s) } +\underset { Sodiumhydroxide\\ \quad (hot) }{ 2NaOH(aq) } \rightarrow \underset { Sodiumaluminate\\ \quad (Soluble) }{ { 2NaAIO }_{ 2 }(aq) } +\underset { Water }{ { H }_{ 2 }O(I) } \)
    The iron oxide and silica (sand) present in the bauxite ore do not dissolve in sodium hydroxide solution. Therefore, they are separated by filtration.
       (ii) \(\underset { Sodiumaluminate }{ { NaAIO }_{ 2 }(aq) } +\underset { Water }{ { 2H }_{ 2 }O(I) } \rightarrow \underset { Aluminiumhydroxide\\ \quad (Whiteppt) }{ { AI(OH) }_{ 3 }(s) } +\underset { Sodiumhydroxide }{ NaOH(aq) } \) 
       (iii) \(\underset { Aluminiumhydroxide }{ { 2AI(OH) }_{ 3 }(s) } \underrightarrow { heat } \underset { Aluminiumoxide\\ \quad (Pure) }{ { AI }_{ 2 }{ O }_{ 3 }(s) } +\underset { Steam }{ { 3H }_{ 2 }O(g) } \)
(b)

Since the metal X react with cold water, it must be high in the reactivity series i.e., sodium or potassium.
X is alkali metal, Na or K.
Since the metal Y reacts with hot water, it must be middle in the reactivity series i.e., magnesium or calcium.
Y is alkaline earth metal, Mg or Ca.
Since the metal X reacts with steam only, it must be low in the reactivity series i.e., iron Z is Fe.
Increasing reactivity series : Na > Mg > Fe.

(i) B is the most active metal as it displaces iron from its salt solution.
(ii) B will displace Cu from CuSO₄ solution because B is more reactive than copper.
(iii) B > A > C > D.

Aluminium and copper metals are used for making cooking vessels because they are good conductors of heat and they have high melting points.

(i) Sodium is a highly reactive metal. It can catch fire if kept in open. Hence to protect it and prevent accidental fire, it is stored under kerosene oil.
(ii) Due to high reactivity of aluminium, a thin layer of aluminium oxide is formed on it. This protective layer of aluminium oxide prevents the metal from further corrosion. Hence, aluminium can be used for making utensils. This process is anodising

Non-metal (lustrous) = Iodine (I)
Metal (non-lustrous) = Sodium (Na)

Metal- mercury, Non-metal- bromine.

Solder is an alloy of lead and tin.

While making an alloy of metal and metal, if one of the metal is mercury then it is called amalgam, 
e.g., Ag + Hg → silver amalgam

Silver when left exposed in air turns black due to the coating of silver sulphide, copper turns green due to the coating of copper carbonate.

Bonds formed between a metal and a non-metal by the transfer of electrons are known as ionic bonds.
e.g., Na⁺+Cl⁻→NaCl

Sulphur dioxide oxidises hydrogen sulphide (H₂ S) to sulphur (S).
SO₂(g)+2H₂S(aq)→3S(s)+2H₂O(I)

Since compound B has molecular mass 40, it must be sodium hydroxide. When sodium hydroxide is treated with aluminium oxide, it gives sodium aluminate. Then the compound A must be sodium.
A - Sodium Na; B - Sodium hydroxide NaOH; C - Sodium aluminate NaAIO₂.
\(2Na+{ 2H }_{ 2 }O\rightarrow 2NaOH+{ H }_{ 2 }\\ { AI }_{ 2 }{ O }_{ 3 }+2NaOH\rightarrow { 2NaAIO }_{ 2 }+{ H }_{ 2 }O\)

Solder is an alloy of lead and tin. Low melting point of solder makes it suitable for welding electrical wires.

It is because HNO₃ is a strong oxidising agent. It oxidises the H₂ produced to H₂O.

Anode (positively charged) Block of the impure metal M. Cathode (negatively charged) Strip of the pure metal M. Electrolyte Aqueous solution of a salt of the metal M.

The metallic oxides which show the properties of acids as well as bases are called amphoteric oxides. It means that they react with both bases and acids to form salt and water.
e.g. ZnO and Al₂O₃
ZnO(s)                         +   2HCl(aq)            \(\rightarrow\) ZnCl₂ (aq)    + H₂O(l)
Zinc oxide (As a base) Hydrochloric acid      Zinc chloride    Water
ZnO(s)                         + 2NaOH(aq)            \(\rightarrow\) Na₂ZnO₂(aq) + H₂O(l)
Zinc oxide (As an acid)  Sodium hydroxide      Sodium zincare   Water

(i) The naturally occurring elements or compounds of metals present in the earth's crust are called minerals.
(ii) Ores are those minerals from which a particular metal can be extracted profitably.
(iii) The undesirable impurities present in the ore are called gangue or matrix.

Different metals react with oxygen at different rates. e.g., Sodium (Na) and potassium (K) catch fire, if left in open. Hence, these are the most reactive metals. To prevent accidental fires, these metals are kept immersed in kerosene oil. Magnesium burns in air only by heating. So, it is less reactive than sodium and potassium. Copper (Cu) does not burn on heating but blister copper burns. Hence the order of reactivity of these metals with oxygen is :
Na >Mg> Cu.
Metals react with water to produce a metal oxide and hydrogen gas. Sodium (Na) and potassium (K) react violently with cold water. So the reaction is violent and exothermic. Magnesium (Mg) does not react with cold water. It reacts with hot water. Metals like lead, copper, silver do not react with water at all. The reactivity series of metals towards water is:
Na > Mg > Cu.

(i) Gold and silver are most malleable metal and most ductile metal,
(ii) Silver is the best conductor of heat and lead is the poorest conductor of heat.
(iii) Metal with highest melting point - Tungsten, iron. Metal with lowest melting point - Gallium, Cesium.

Sodium and potassium react vigorously with cold water.
When these metals are dropped in water, bubbles will be evolved due to evolution of hydrogen gas, large amount of heat is produced and the solution will change red litmus blue.
Hydrogen gas is formed. Bring burning splinter near the mouth of the test tube where gas is evolved, the splinter bums with a pop sound. 

Haematite (Fe₂O₃) is an important ore of iron.
In the upper part of the blast furnace, carbon monoxide reduces iron (III) oxide to iron metal.
\(\underset { Iron(III)oxide }{ { Fe }_{ 2 }{ O }_{ 3 } } +\underset { Carbonmonoxide }{ 3CO(g) } \rightarrow \underset { Ironmetal }{ 2Fe(I) } +\underset { Carbondioxide }{ { 3CO }_{ 2 }(g) } \)
Following reactions are involved in the blast furnace:
(i) Formation of carbon monoxide
\(\underset { Carbon }{ C(s) } +\underset { Oxygen }{ { O }_{ 2 }(g) } \rightarrow \underset { Carbondioxide }{ { CO }_{ 2 }(g) } +Heat\\ \underset { Carbondioxide }{ { CO }_{ 2 }(g) } +\underset { Coke }{ C(s) } \rightarrow \underset { Carbonmonoxide }{ 2CO(g) } \)
(ii) Reduction of iron (III) oxide or haematite to iron
\(\underset { Iron(III)oxide }{ { Fe }_{ 2 }{ O }_{ 3 } } +\underset { Carbonmonoxide }{ 3CO(g) } \rightarrow \underset { Ironmetal }{ 2Fe(I) } +\underset { Carbondioxide }{ { 3CO }_{ 2 }(g) } \)