Unit I: Basic and Inorganic Chemistry Module 3. Chemistry of metals Part A – lecture (1 hr) Characteristics of Metals The chemists can easily differentiate between metals and non-metals based on their placement on the Periodic Table of the Elements. The metals are elements that are found to the left of a group of elements referred to as the metalloids. The metalloids are a group of elements which have properties similar to both the metals and nonmetals.

Electronic Nature of Metals Metals are the elements which form positive ions by losing electrons. Metals have 1 to 3 electrons in the outermost shell of their atom. Occurrence of Metals Metals like gold and platinum occur in the free metallic form not acted upon by air or water The rest of the metals occur in the combined form as compounds. Copper is one of the metals which occur in free as well as combined state. Aluminium is the most abundant metal in the earth's crust. The second most abundant metal in the earth is iron and the third one is calcium

Minerals and Ores Metals and their compounds are found in earth as natural elements known as minerals. Ores are minerals from which metals are extracted at low cost with minimum effort. Ores contains metal compounds with a percentage of impurities. Type Native metals Carbonates

Halides Oxides

Phosphates Silicates Sulfides Sulfates

Examples of Minerals silver, gold, bismuth, copper, palladium, platinum witherite (BaCO3), calcite or limestone (CaCO3), magnesite (MgCO3), dolomite (CaCO3·MgCO3), cerussite (PbCO3), smithsonite (ZnCO3) fluorite (CaF2), halite (NaCl), sylvite (KCl), cryolite (Na3AlF6) Bauxite (Al2O3·2H2O), corundum (Al2O3), hematite (Fe2O3), magnetite (Fe3O4), cuprite (Cu2O), pyrolusite (MnO2), cassiterite (SnO2), rutyle (TiO2), zincite (ZnO) Phosphate rock (Ca3(PO4)2). hydroxyapatite (Ca5(PO4)3OH) Beryl (Be3Al2Si6O18), zircon (ZrSiO4), albite (NaAlSi3O8), talc (Mg3(Si4O10)(OH)2 Argentite (Ag2S), greenockite (CdS), chalcocite (Cu2S), pyrite (FeS2), cinnabar (HgS), galena (PbS), sphalerite (ZnS) Barite (BaSO4), anhydrite (CaSO4), anglesite (PbSO4)

Metallurgy Metallurgy is the science and technology of separating metals from their ores and of compounding alloys. An alloy is a solid solution composed of two or more metals, or of a metal or metals with one or more nonmetals. The three principal steps in the recovery of a metal from its ore are preparation of the ore, production of the metal and purification of the metal. • Preparation of the ore In the preliminary treatment of an ore, the desired mineral is separated from waste materials – usually clay and silicate minerals – which are collectively called the gangue. One of the very useful method for carrying out such a separation is flotation - the ore is finely ground and added to water containing oil and detergent. The oil preferentially wets the mineral particles, which are then carried to the top in the froth, while the gangue settles to bottom. Another physical separation process makes use of the magnetic properties of certain minerals e.g. magnetite. To extract metal from ore also an amalgams (an alloy of mercury with another metals) are also used.

• Production of metals Because metals in their combined forms always have positive oxidation numbers, the production of a free metal is always a reduction process. Metal Lithium, sodium, magnesium, calcium Aluminium Chromium, manganese, titanium, vanadium, iron, zinc Mercury, silver, platinum, copper, gold

Reduction process Electrolytic reduction of molten chloride Electrolytic reduction of anhydrous oxide (in molten cryolite) Reduction of the metal oxide with a more electropositive metal, or reduction with coke and carbon monoxide These metals occur in the free state or can be obtained by roasting their sulfides

• Purification of metals Metals prepared by reduction usually need further treatment to remove various impurities . The extent of purification depends on the use to be made of the metal. The most common purification procedures are distillation, electrolysis and zone refining.

Chemical Properties of Metals •

The reaction of some metals with air, water and acids

Part B – laboratory (3 hrs) I. Chemical base of metallurgy Purpose: To acquaint students with process of metals production by reduction.. Substances: PbO, PbO2, Ag2O, CuO, ZnO, ZnS, SnO2, Fe2O3, pieces of charcoal The metals industry has long used chemistry in isolating metals. Two of the common procedures used are roasting and smelting. The roasting process involves heating the ore to decompose unstable ions which are bonded to the metal. Some examples are given below, where M represents a metal ion: • • •

MCO3(s) MO(s) + CO2(g) MSO3(s) MO(s) + SO2(g) MOH(s) MO(s) + H2O(g)

In each case, the second product is gaseous and is simply expelled to the environment. The metal oxide (MO) is purified by heating with powdered charcoal. This is the key to smelting. A replacement reaction occurs as follows: •

MO(s) + C CO2(g) + M(s)

Thus, the metal is released and can be isolated by any of several methods e.g. flotation.

Procedure: To carry out the reduction process by putting a small amount of metal oxide on a piece of charcoal and playing a flame on the oxide using blow-pipe. After oxide reduction, put obtained lump of metal in a test tube and add few cm3 HNO3 to remove remaining oxide. II. Gold and silver coins A Purpose : To acquaint students with the process of galvanization Making the silver coins Substances : copper-colored clean coins, powder zinc metal, 2M sodium hydroxide solution, tongs, burner. Procedure: 1) Add 1 gram of powder zinc to a 30 ml of 2M NaOH solution. 2) Heat the mixture to near-boiling, then remove it from heat. 3) Add clean coins to the solution. 4) Wait 5-10 minutes for them to turn silver, then use tongs to remove the coins from the solution. 5) Rinse the coins in water, and then set them on a towel to dry.

This chemical reaction plates the copper in the penny with zinc. This is called galvanization. The zinc reacts with the hot sodium hydroxide solution to form soluble sodium zincate, Na2ZnO2, which is converted to metallic zinc when it touches the surface of the penny. III. How to make the silver coins turn gold Procedure: 1. 2. 3. 4.

Grasp a silver coin with tongs. Gently heat the penny in the outer (cool) part of a burner flame Remove the penny from heat as soon as it changes color. Rinse the gold coin under water to cool it.

Heating the coins fuses the zinc and copper to form an alloy called brass. Brass is a homogeneous metal (alloy) that varies from 60-82% Cu and from 18-40% Zn. Brass has a relatively low melting point, so the coating can be destroyed by heating the coins for too long. IV. Pushing out metal from its solution by the other metals Equipment : set of vials, burner. Substances : 1 molar solution of Cu(NO3)2; CuSO4; CuCl2; AgNO3; HgCl2; FeSO4; Zn; Al; Cu (metal strip or wire). Procedure : 1. Put a small strip of Zn into the vials with the solution of Cu(NO3)2; CuSO4; CuCl2 and shake energetically. Compare the results. Does the presence of different anions influence the results of experiment ? Write down the equation of chemical reaction in an ionic form according to the scheme mM1n+ + nM20 = mM10 + nM2m+ 2. Put a small strip of Zn or Al into the vials with the solution of AgNO3; HgCl2; FeSO4. Write down the equation of chemical reactions in an ionic form. 3. Conduct analogous test with Cu and the solutions of AgNO3 ; HgCl2. Write down the equation of chemical reactions in an ionic form. On basis of experimental results formulate the principle of mutual pushing out the metals from solutions.