Hydrogen peroxide \[({{H}_{2}}{{O}_{2}})\] was discovered by French chemist Thenard.
(1) Preparation : It is prepared by
(i) Laboratory method : In laboratory, \[{{H}_{2}}{{O}_{2}}\] is prepared by Merck's process. It is prepared by adding calculated amounts of sodium peroxide to ice cold dilute (20%) solution of \[{{H}_{2}}S{{O}_{4}}\].
\[N{{a}_{2}}{{O}_{2}}+{{H}_{2}}S{{O}_{4}}\xrightarrow{{}}N{{a}_{2}}S{{O}_{4}}+{{H}_{2}}{{O}_{2}}\]
(ii) By the action of sulphuric acid or phosphoric acid on hydrated barium peroxide \[Ba{{O}_{2}}.8{{H}_{2}}O\]
(a) \[Ba{{O}_{2}}.8{{H}_{2}}O+{{H}_{2}}S{{O}_{4}}\to BaS{{O}_{4}}\downarrow +{{H}_{2}}{{O}_{2}}+8{{H}_{2}}O\]
It must be noted that anhydrous barium peroxide does not react readily with sulphuric acid (because a coating of insoluble barium sulphate is formed on its surface which stops further action of the acid). Therefore, hydrated barium peroxide, \[Ba{{O}_{2}}.8{{H}_{2}}O\] must be used.
(b) \[3Ba{{O}_{2}}+2{{H}_{3}}P{{O}_{4}}\to B{{a}_{3}}{{(P{{O}_{4}})}_{2}}+3{{H}_{2}}{{O}_{2}}\]
\[B{{a}_{3}}{{(P{{O}_{4}})}_{2}}+3{{H}_{2}}S{{O}_{4}}\to 3BaS{{O}_{4}}+2{{H}_{3}}P{{O}_{4}}\]
Phosphoric acid is preferred to \[{{H}_{2}}S{{O}_{4}}\] because soluble impurities like barium persulphate (from \[Ba{{O}_{2}}.8{{H}_{2}}O+{{H}_{2}}S{{O}_{4}}\]) tends to decompose \[{{H}_{2}}{{O}_{2}}\] while \[{{H}_{3}}P{{O}_{4}}\] acts as preservative (negative catalyst) for \[{{H}_{2}}{{O}_{2}}\].
(iii) Industrial method : On a commercial scale, \[{{H}_{2}}{{O}_{2}}\] can be prepared by the electrolysis of 50% \[{{H}_{2}}S{{O}_{4}}\] solution. In a cell, peroxy disulphuric acid is formed at the anode.
\[2{{H}_{2}}S{{O}_{4}}\xrightarrow[\text{Elecrolysis}]{}\underset{\begin{smallmatrix} \text{Peroxy disulphuric} \\ \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\text{acid} \end{smallmatrix}}{\mathop{{{H}_{2}}{{S}_{2}}{{O}_{8}}(aq.)}}\,+{{H}_{2}}(g)\]
This is drawn off from the cell and hydrolysed with water to give \[{{H}_{2}}{{O}_{2}}\].
\[{{H}_{2}}{{S}_{2}}{{O}_{8}}+2{{H}_{2}}O\xrightarrow{{}}2{{H}_{2}}S{{O}_{4}}+{{H}_{2}}{{O}_{2}}\]
The resulting solution is distilled under reduced pressure when \[{{H}_{2}}{{O}_{2}}\] gets distilled while \[{{H}_{2}}S{{O}_{4}}\] with high boiling point, remains undistilled.
(iv) By redox process : Industrially \[{{H}_{2}}{{O}_{2}}\] is prepared by the auto-oxidation of 2-alkylanthraquinols. The process involves a cycle of reactions. The net reaction is the catalytic union of \[{{H}_{2}}\] and \[{{O}_{2}}\] to give \[{{H}_{2}}{{O}_{2}}\].
The \[{{H}_{2}}{{O}_{2}}\] formed (about 1%) is extracted with water and concentrated.
(2) Physical properties
(i) Pure hydrogen peroxide is a pale blue syrupy liquid.
(ii) It freezes at - 0.5°C and has a density of 1.4 in pure state.
(iii) Hydrogen peroxide is diamagnetic.
(iv) It is more highly associated via hydrogen bonding than water.
(v) Although it is a better polar solvent than \[{{H}_{2}}O\].
However, it can?t be used as such because of strong autooxidation ability.
(vi) Dipole moment of \[{{H}_{2}}{{O}_{2}}\] is 2.1 D.
(3) Chemical properties
(i) Decomposition : Pure \[{{H}_{2}}{{O}_{2}}\] is an unstable liquid and decomposes into water and \[{{O}_{2}}\] either upon standing or upon heating, \[2{{H}_{2}}{{O}_{2}}\xrightarrow{{}}2{{H}_{2}}O+{{O}_{2}};\,\,\,\Delta H=-196.0\,kJ\]
(ii) Oxidising nature : It is a powerful oxidising agent. It acts as an oxidising agent in neutral, acidic or in alkaline medium. e.g. \[2KI+{{H}_{2}}{{O}_{2}}\xrightarrow{{}}2KOH+{{I}_{2}}\] [In neutral medium]
\[2FeS{{O}_{4}}+{{H}_{2}}S{{O}_{4}}+{{H}_{2}}{{O}_{2}}\xrightarrow{{}}F{{e}_{2}}{{(S{{O}_{4}})}_{3}}+2{{H}_{2}}O\] [In acidic medium]
\[MnS{{O}_{4}}+{{H}_{2}}{{O}_{2}}+2NaOH\xrightarrow{{}}Mn{{O}_{2}}+N{{a}_{2}}S{{O}_{4}}+2{{H}_{2}}O\]
[In alkaline medium]
(iii) Reducing nature : \[{{H}_{2}}{{O}_{2}}\] has tendency to take up oxygen from strong oxidising agents and thus, acts as a reducing agent, \[\underset{\begin{smallmatrix} \text{From oxidising } \\ \,\,\,\,\,\,\,\,\,\,\text{agent} \end{smallmatrix}}{\mathop{{{H}_{2}}{{O}_{2}}+O\xrightarrow{{}}{{H}_{2}}O+{{O}_{2}}}}\,\]. It can act as a reducing agent in acidic, basic or even neutral medium.
In acidic medium, \[{{H}_{2}}{{O}_{2}}\xrightarrow{{}}2{{H}^{+}}+{{O}_{2}}+2{{e}^{-}}\]
In alkaline medium, \[{{H}_{2}}{{O}_{2}}+2O{{H}^{-}}\xrightarrow{{}}2{{H}_{2}}O+{{O}_{2}}+2{{e}^{-}}\]
(iv) Bleaching action : \[{{H}_{2}}{{O}_{2}}\] acts as a bleaching agent due to the release of nascent oxygen.
\[{{H}_{2}}{{O}_{2}}\xrightarrow{{}}{{H}_{2}}O+O\]
Thus, the bleaching action of \[{{H}_{2}}{{O}_{2}}\] is due to oxidation. It oxidises the colouring matter to a colourless product, Colouring matter + O \[\to \] Colour less matter. more...
Water is the oxide of hydrogen. It is an important component of animal and vegetable matter. Water constitutes about 65% of our body. It is the principal constituent of earth's surface.
(1) Structure : Due to the presence of lone pairs, the geometry of water is distorted and the \[H-O-H\] bond angle is 104.5°, which is less than the normal tetrahedral angle (109.5°). The geometry of the molecule is regarded as angular or bent. In water, each \[O-H\]bond is polar because of the high electronegativity of oxygen (3.5) in comparison to that of hydrogen (2.1). The resultant dipole moment of water molecule is 1.84D.
In ice, each oxygen atom is tetrahedrally surrounded by four hydrogen atoms; two by covalent bonds and two by hydrogen bonds. The resulting structure of ice is open structure having a number of vacant spaces. Therefore, the density of ice is less than that of water and ice floats over water. It may be noted that water has maximum density \[(1g\,c{{m}^{-3}})\]at 4°C (277 K).
(2) Heavy water : Chemically heavy water is deuterium oxide\[({{D}_{2}}O)\]. It was discovered by Urey.
It is obtained as a by-product in some industries where \[{{H}_{2}}\] is produced by the electrolysis of water.
Heavy water \[({{D}_{2}}O)\] is used (a) as a moderator and coolant in nuclear reactors (b) in the study of mechanism of chemical reactions (c) as a starting material for the preparation of a number of deuterium compounds, e.g.,
\[S{{O}_{3}}+{{D}_{2}}O\to \underset{\text{Deuteriosulphuric acid}}{\mathop{{{D}_{2}}S{{O}_{4}}}}\,\]
\[A{{l}_{4}}{{C}_{3}}+12\,{{D}_{2}}O\to \underset{\text{Deuteromethane}}{\mathop{3C{{D}_{4}}}}\,+\ \ \ \ 4Al{{(OD)}_{3}}\]
\[Ca{{C}_{2}}+2{{D}_{2}}O\to \underset{\text{Deuterioa}\text{cetylene}}{\mathop{{{C}_{2}}{{D}_{2}}}}\,+\ \ \ Ca{{(OD)}_{2}}\]
(3) Physical properties : Water is colourless, odourless and tasteless liquid at ordinary temperature.
At 273K water is in equilibrium with ice and vapour this point is known triple point.
Some physical constants of H2O and D2O at 298 K
(1) Position of hydrogen in the periodic table
Hydrogen is the first element in the periodic table. Hydrogen is placed in no specific group due to its property of giving electron (When \[{{H}^{-}}\] is formed) and also losing electron (When \[{{H}^{+}}\]is formed).
(i) Hydrogen is placed in group I (Alkali metals) as,
(a) It has one electron in its (Outer) shell-\[1{{s}^{1}}\] like other alkali metals which have (inert gas) \[n{{s}^{1}}\] configuration.
(b) It forms monovalent \[{{H}^{+}}\] ion like \[L{{i}^{+}},\ N{{a}^{+}}\ldots \]
(c) Its valency is also 1.
(d) Its oxide \[({{H}_{2}}O)\] is stable as \[L{{i}_{2}}O,\ N{{a}_{2}}O\].
(e) It is a good reducing agent (In atomic as well as molecular state) like \[Na\text{, }Li\ldots \]
(ii) Hydrogen also resembles halogens (Group VII A) as,
(a) It is also diatomic \[({{H}_{2}})\]like \[{{F}_{2}},\ C{{l}_{2}}\ldots \]
(b) It also forms anion \[{{H}^{-}}\] like \[{{F}^{-}},\ C{{l}^{-}}\ldots \] by gain of one electron.
(c) \[{{H}^{-}}\] has stable inert gas \[(He)\] configuration as \[C{{H}_{4}},{{C}_{2}}{{H}_{6}}\] like halogens \[CC{{l}_{4}},S{{F}_{2}}C{{l}_{2}}\] etc.
(d) H is one electron short of duplet (Stable configuration) like \[F,\ Cl,\ldots \] which are also one electron deficient than octet,\[F-2{{s}^{2}}2{{p}^{5}}\]; \[Cl-3{{s}^{2}}3{{p}^{5}}\].
(e) (IE) of \[H(1312\ kJ\ mo{{l}^{-1}})\] is of the same order as that of halogens.
(iii) (IE) of H is very high in comparison with alkali metals. Also size of \[{{H}^{+}}\] is very small compared to that of alkali metal ion. H forms stable hydride only with strongly electropositive metals due to smaller value of its electron affinity \[(72.8\,kJ\ mo{{l}^{-1}})\].
(iv) In view of the anomalous behaviour of hydrogen, it is difficult to assign any definite position to it in the periodic table. Hence it is customary to place it in group I (Along with alkali metals) as well as in group VII (Along with halogens).
(2) Discovery and occurrence : It was discovered by Henry Cavendish in 1766. Its name hydrogen was proposed by Lavoisier. Hydrogen is the 9th most abundant element in the earth's crust.
Hydrogen exists in diatomic state but in triatomicstate it is called as Hyzone. Systematic name of water is oxidane.
(3) Preparation of Dihydrogen : Dihydrogen can be prepared by the following methods,
(i) By action of water with metals
(a) Active metals like Na, K react at room temperature
\[2M+2{{H}_{2}}O\to 2MOH+{{H}_{2}}\] [M = Na, K etc.]
(b) Less active metals like Ca, Zn, Mg, Al liberate hydrogen only on heating.
\[2Al+3{{H}_{2}}O\to A{{l}_{2}}{{O}_{3}}+3{{H}_{2}}\]
(c) Metals like Fe, Ni, Co, Sn can react only when steam is passed over red hot metals.
\[3Fe+4{{H}_{2}}O(\text{steam})\to \underset{\text{Ferrosoferric oxide}}{\mathop{F{{e}_{3}}{{O}_{4}}}}\,+4{{H}_{2}}\]
(ii) By the action of water on alkali and alkaline earth metals hydrides
\[NaH+{{H}_{2}}O\to NaOH+{{H}_{2}}\]
\[Ca{{H}_{2}}+2{{H}_{2}}O\to Ca{{(OH)}_{2}}+2{{H}_{2}}\]
(iii) By reaction of metals like Zn, Sn, Al with alkalies (NaOH or KOH)
\[Zn+2NaOH\xrightarrow{\Delta }\underset{\text{sod}\text{. zincate}}{\mathop{N{{a}_{2}}Zn{{O}_{2}}}}\,+{{H}_{2}}\]
\[Al+2NaOH+{{H}_{2}}O\xrightarrow{\Delta }\underset{\text{Sod}\text{. meta-aluminate}}{\mathop{2NaAl{{O}_{2}}}}\,+2{{H}_{2}}\]
\[\underset{\text{Silicon}}{\mathop{Si}}\,+2NaOH+2{{H}_{2}}O\xrightarrow{\Delta }N{{a}_{2}}Si{{O}_{3}}+3{{H}_{2}}\]
\[\underset{\text{Tin}}{\mathop{Sn}}\,+2NaOH\xrightarrow{\Delta }\underset{\text{Sod}\text{. stannite}}{\mathop{N{{a}_{2}}Sn{{O}_{2}}}}\,+{{H}_{2}}\uparrow \]
(iv) By action of metal with acids : All active metals which lie above hydrogen in electrochemical series, can displace hydrogen gas from dilute mineral acids like HCl, \[{{H}_{2}}S{{O}_{4}}\].
\[Fe+2HCl\to FeC{{l}_{2}}+{{H}_{2}}\]
(v) By the electrolysis of acidified water
\[2{{H}_{2}}O\xrightarrow{{{H}^{+}}/\text{Electrolysis}}\underset{\text{At cathode}}{\mathop{2{{H}_{2}}\uparrow }}\,+\underset{\text{At anode}}{\mathop{{{O}_{2}}\uparrow }}\,\] more...
Element which have low chemical reactivity generally occur native or free or metallic state. e.g. \[Au,\,Pt,\,\]noble gas etc. Element which are chemically reactive, generally occur in the combined state. e.g. halogens, chalcogens etc. The natural materials in which the metals occur in the earth are called minerals. The mineral from which the metal is conveniently and economically extracted is called an ore. All the ores are minerals but all minerals cannot be ores. Ores may be divided into four groups,
(1) Metallic core (siderophile) of the earth crust contains (Mn, Fe, Co, Ni, Cu, Ru, Rb, Pd, Ag, Re, Os, Ir, Pt, Au). Entire composition of metals in earth crust may be given as,
Al (8.3%); Ca(3.6%); Na (2.8%); K (2.6%); Mg (2.1%); Ti (0.4%); Mn (0.1%); Fe (5.1%) other metals (0.1%).
(i) Native ores : These ores contain metals in free state, e.g., silver, gold, platinum, mercury, copper, etc. These are found usually associated with rock or alluvial materials like clay, sand, etc. sometimes lumps of pure metals are also found. These are termed nuggets. Iron is found in free state as meteroites which also have 20 to 30% nickel.
(ii) Sulphurised and arsenical ores : These ores consist of sulphides and arsenides in simple and complex forms of metals. Important ores of this group are
Metal
Name of the ore
Composition
Pb
Galena
PbS
Zn
Zinc blende
ZnS
Hg
Cinnabar
HgS
Ag
Argentite or silver glance Pyrargyrite or ruby silver
Metals are also found in living organisms, e.g.,
(1) Magnesium is found in chlorophyll.
(2) Potassium is present in plant roots.
(3) Manganese, Iron and copper are present in chloroplast.
(4) Zinc is present in eyes of cats and cows.
(5) Iron is present in haemoglobin.
(6) Calcium is present in bones.
(7) Vanadium is present in cucumbers.
(8) Chromium is present in prown.
The extraction of a pure metal from its ore is called metallurgy. In order to extract the metal from ores, several physical and chemical methods are used. The method used depending upon chemical properties and nature of the ore from which it is to be extracted. It involves four main steps,
(1) Crushing and grinding of the ore.
(2) Concentration or dressing of the ore.
(3) Reduction to free metal.
(4) Purification or refining of the metal.
(1) Crushing and grinding of the ore : Those ores occur in nature as huge lumps. They are broken to small pieces with the help of crushers or grinders. These pieces are then reduced to fine powder with the help of a ball mill or stamp mill. This process is called pulverisation.
(2) Concentration or dressing of the ore : The ore are usually obtained from the ground and therefore contained large amount of unwanted impurities, e.g., earthing particles, rocky matter, sand, limestone etc. These impurities are known collectively as gangue or matrix. It is essential to separate the large bulk of these impurities from the ore to avoid bulk handling and in subsequent fuel costs. The removal of these impurities from the ores is known as concentration. The concentration is done by physical as well as chemical methods.
Physical Methods (i) Gravity Separation or levigation: This process of concentration is based on the difference in the specific gravity of the ore and gangue. The sieved ore is either subjected to dry centrifugal separation or is placed in big shallow tanks in which a strong current of water blows. Heavy ore particles settle down to the bottom of the tanks while lighter gangue particles are carried away by the current of water. The process removes most of the soluble and insoluble impurities. For this purpose wilfley table and hydraulic classifier are widely used. The method is particularly suitable for heavy oxide and carbonate ores like Cassiterite (SnO2) and haematite.
(ii) Froth floatation process : In some cases for example, sulphides ores of copper, zinc and lead concentration is brought by this method. In this method advantage is taken of the preferential wetting of the ore by an oil. The finely ground ore is taken in a tank containing water and 1% of pine oil or terpentine oil. A strong current of air is blown through the suspension, producing a heavy froth or foam on the surface. The metal sulphide is wetted by the oil but the gangues is not and the sulphide-oil mixture is carried to the surface by films of oil The froth is skimmed off, the gangue settles down on the bottom or remains underneath the froth. By this floatation method it is possible to concentrate over 90% of a sulphite ore to 1/10 of its original bulk.
(ii) Activators and Depressants : During the floatation process of more...
Different metallurgical processes can be broadly divided into three main types
(1) Pyrometallurgy : Extraction is done using heat energy. The metals like \[Cu,\,Fe,\text{ }Zn,\,Pb,\,Sn,\,Ni,\,Cr,\,Hg\] etc. Which are found in the nature in the form of oxides, carbonates, sulphides are extracted by this process.
(2) Hydrometallurgy : Extraction of metals involving aqueous solution is known as hydrometallurgy. Silver, gold etc are extracted by this process.
(3) Electrometallurgy : Extraction of highly reactive metals such as \[Na,\,K,\,Ca,\,Mg,\,Al\] etc. by carrying electrolysis of one of the suitable compound in fused or molten state.
The materials which can withstand very high temperatures without melting or becoming soft are known as refractory materials. These are not affected by slags formed during the extraction of metals. These are used in the form of bricks for the internal linings of furnaces. Refractory materials used are of three types,
(1) Acid refractories : Silica, quartz, silicious sand stones, etc., are the examples.
(2) Basic refractories : Lime, dolomite, magnesite, etc., are the examples.
(3) Neutral refractories : Graphite, chromite, bone ash, etc., are the examples.
Silica \[(92%\ Si{{O}_{2}},\ 2.7%\ A{{l}_{2}}{{O}_{3}})\] and quartz, can tolerate temperatures upto about 1750°C, bauxite upto 1800°C, alumina upto 2000°C and magnesite, chromite, etc., upto 2200°C. Some carbides such as silicon carbide is used as refractory for special purposes.
A metallic product containing two or more metals or sometimes one of the ingredients a non-metal provided that the mixture is homogenous and possesses metallic properties, is known as an alloy. Alloys are usually prepared by melting two or more metals together in the proportions and then allowing the melting to solidify. If one of the metals is mercury the alloy is known as amalgam.
Alloys are prepared with a view to impart some desirable properties which the individual metals do not possess. These are,
(1) Change in the chemical reactivity : Sodium acts vigorously with water, but Na-Hg amalgam reacts slowly to suit the requirement of a number of chemical reactions.
(2) Hardness : Silver, gold and soft metals but become hard when alloyed with copper.
(3) Melting Points : Melting points of an alloy may be higher or lower than any of its components. Wood-metal, which is an alloy of Bi, Pb, Sn and Cd fuses at 60.5oC., while none of these metals fuses at this low temperature.
(4) Change of colour : Aluminium bronze is an alloy of aluminium and copper. It is of golden, yellow colour and is used in making decoration articles, jewellery and coins while the colour of aluminium is white and that of copper is red.
(5) Corrosion resistance : Iron gets corroded soon whereas stainless Steel, an alloy of iron and chromium, resists corrosion.
(6) Casting : An alloy of lead and antimony is known as type metal is used for casting type required in printing works.
Alloys of Al
Alloy
Percentage
Important Properties
Uses
Aluminium bronze
Al Cu
95% 5%
Light, strong alloy with golden lustre, resistant to corrosion
The \[{{H}_{2}}{{O}_{2}}\] formed (about 1%) is extracted with water and concentrated.
(2) Physical properties
(i) Pure hydrogen peroxide is a pale blue syrupy liquid.
(ii) It freezes at - 0.5°C and has a density of 1.4 in pure state.
(iii) Hydrogen peroxide is diamagnetic.
(iv) It is more highly associated via hydrogen bonding than water.
(v) Although it is a better polar solvent than \[{{H}_{2}}O\].
However, it can?t be used as such because of strong autooxidation ability.
(vi) Dipole moment of \[{{H}_{2}}{{O}_{2}}\] is 2.1 D.
(3) Chemical properties
(i) Decomposition : Pure \[{{H}_{2}}{{O}_{2}}\] is an unstable liquid and decomposes into water and \[{{O}_{2}}\] either upon standing or upon heating, \[2{{H}_{2}}{{O}_{2}}\xrightarrow{{}}2{{H}_{2}}O+{{O}_{2}};\,\,\,\Delta H=-196.0\,kJ\]
(ii) Oxidising nature : It is a powerful oxidising agent. It acts as an oxidising agent in neutral, acidic or in alkaline medium. e.g. \[2KI+{{H}_{2}}{{O}_{2}}\xrightarrow{{}}2KOH+{{I}_{2}}\] [In neutral medium]
\[2FeS{{O}_{4}}+{{H}_{2}}S{{O}_{4}}+{{H}_{2}}{{O}_{2}}\xrightarrow{{}}F{{e}_{2}}{{(S{{O}_{4}})}_{3}}+2{{H}_{2}}O\] [In acidic medium]
\[MnS{{O}_{4}}+{{H}_{2}}{{O}_{2}}+2NaOH\xrightarrow{{}}Mn{{O}_{2}}+N{{a}_{2}}S{{O}_{4}}+2{{H}_{2}}O\]
[In alkaline medium]
(iii) Reducing nature : \[{{H}_{2}}{{O}_{2}}\] has tendency to take up oxygen from strong oxidising agents and thus, acts as a reducing agent, \[\underset{\begin{smallmatrix} \text{From oxidising } \\ \,\,\,\,\,\,\,\,\,\,\text{agent} \end{smallmatrix}}{\mathop{{{H}_{2}}{{O}_{2}}+O\xrightarrow{{}}{{H}_{2}}O+{{O}_{2}}}}\,\]. It can act as a reducing agent in acidic, basic or even neutral medium.
In acidic medium, \[{{H}_{2}}{{O}_{2}}\xrightarrow{{}}2{{H}^{+}}+{{O}_{2}}+2{{e}^{-}}\]
In alkaline medium, \[{{H}_{2}}{{O}_{2}}+2O{{H}^{-}}\xrightarrow{{}}2{{H}_{2}}O+{{O}_{2}}+2{{e}^{-}}\]
(iv) Bleaching action : \[{{H}_{2}}{{O}_{2}}\] acts as a bleaching agent due to the release of nascent oxygen.
\[{{H}_{2}}{{O}_{2}}\xrightarrow{{}}{{H}_{2}}O+O\]
Thus, the bleaching action of \[{{H}_{2}}{{O}_{2}}\] is due to oxidation. It oxidises the colouring matter to a colourless product, Colouring matter + O \[\to \] Colour less matter. more... 
In ice, each oxygen atom is tetrahedrally surrounded by four hydrogen atoms; two by covalent bonds and two by hydrogen bonds. The resulting structure of ice is open structure having a number of vacant spaces. Therefore, the density of ice is less than that of water and ice floats over water. It may be noted that water has maximum density \[(1g\,c{{m}^{-3}})\]at 4°C (277 K).
(2) Heavy water : Chemically heavy water is deuterium oxide\[({{D}_{2}}O)\]. It was discovered by Urey.
It is obtained as a by-product in some industries where \[{{H}_{2}}\] is produced by the electrolysis of water.
Heavy water \[({{D}_{2}}O)\] is used (a) as a moderator and coolant in nuclear reactors (b) in the study of mechanism of chemical reactions (c) as a starting material for the preparation of a number of deuterium compounds, e.g.,
\[S{{O}_{3}}+{{D}_{2}}O\to \underset{\text{Deuteriosulphuric acid}}{\mathop{{{D}_{2}}S{{O}_{4}}}}\,\]
\[A{{l}_{4}}{{C}_{3}}+12\,{{D}_{2}}O\to \underset{\text{Deuteromethane}}{\mathop{3C{{D}_{4}}}}\,+\ \ \ \ 4Al{{(OD)}_{3}}\]
\[Ca{{C}_{2}}+2{{D}_{2}}O\to \underset{\text{Deuterioa}\text{cetylene}}{\mathop{{{C}_{2}}{{D}_{2}}}}\,+\ \ \ Ca{{(OD)}_{2}}\]
(3) Physical properties : Water is colourless, odourless and tasteless liquid at ordinary temperature.
At 273K water is in equilibrium with ice and vapour this point is known triple point.
Some physical constants of H2O and D2O at 298 K
(ii) Froth floatation process : In some cases for example, sulphides ores of copper, zinc and lead concentration is brought by this method. In this method advantage is taken of the preferential wetting of the ore by an oil. The finely ground ore is taken in a tank containing water and 1% of pine oil or terpentine oil. A strong current of air is blown through the suspension, producing a heavy froth or foam on the surface. The metal sulphide is wetted by the oil but the gangues is not and the sulphide-oil mixture is carried to the surface by films of oil The froth is skimmed off, the gangue settles down on the bottom or remains underneath the froth. By this floatation method it is possible to concentrate over 90% of a sulphite ore to 1/10 of its original bulk.
(ii) Activators and Depressants : During the floatation process of
