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    Zinc

    Uploaded by

    Perish Raj Thapa
    1. Zinc can be extracted from its ores like zinc blende through crushing, concentration by froth floatation, roasting to form zinc oxide, and reduction using coke to produce zinc vapor. 2. The zinc vapor is then purified through distillation or electrolysis to produce 99-99.5% pure zinc. 3. Zinc reacts with air to form zinc carbonate and with acids to produce hydrogen gas; it can also displace less reactive metals from their salts and is used to galvanize iron.

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    Zinc

    Uploaded by

    Perish Raj Thapa
    85 views6 pages
    1. Zinc can be extracted from its ores like zinc blende through crushing, concentration by froth floatation, roasting to form zinc oxide, and reduction using coke to produce zinc vapor. 2. The zinc vapor is then purified through distillation or electrolysis to produce 99-99.5% pure zinc. 3. Zinc reacts with air to form zinc carbonate and with acids to produce hydrogen gas; it can also displace less reactive metals from their salts and is used to galvanize iron.

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    zinc

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    1. Zinc can be extracted from its ores like zinc blende through crushing, concentration by froth floatation, roasting to form zinc oxide, and reduction using coke to produce zinc vapor. 2. The zinc vapor is then purified through distillation or electrolysis to produce 99-99.5% pure zinc. 3. Zinc reacts with air to form zinc carbonate and with acids to produce hydrogen gas; it can also displace less reactive metals from their salts and is used to galvanize iron.

    Copyright:

    © All Rights Reserved
    Download as DOCX, PDF, TXT or read online from Scribd
    Download as docx, pdf, or txt
    85 views6 pages

    Zinc

    Uploaded by

    Perish Raj Thapa
    1. Zinc can be extracted from its ores like zinc blende through crushing, concentration by froth floatation, roasting to form zinc oxide, and reduction using coke to produce zinc vapor. 2. The zinc vapor is then purified through distillation or electrolysis to produce 99-99.5% pure zinc. 3. Zinc reacts with air to form zinc carbonate and with acids to produce hydrogen gas; it can also displace less reactive metals from their salts and is used to galvanize iron.

    Copyright:

    © All Rights Reserved
    Download as DOCX, PDF, TXT or read online from Scribd
    Download as docx, pdf, or txt
    of 6

    Zinc

    Ores of Zinc
    1. Zinc blende: ZnS
    2. Calamine: ZnCO3
    3. Zincite: ZnO

    Extraction of zinc from zinc blende 1. Crushing and pulverization


    Big lumps of ores are crushed using jaw crushers to get crushed ore which is pulverized using a
    pulverizer or stamp mill to get powdered ore.

    2. Concentration by froth floatation process


    The powdered ore is taken in a tank containing water and a small amount of pine oil. The mixture is
    heated by a blast of air. Impurities are wetted by water and get collected at the bottom of the tank.
    Ore particles are wetted by oil and come to the surface as froth. The froth is skimmed off to collect
    concentrated ore.

    Fig: Froth floatation process

    3. Roasting
    The concentrated ore is roasted at 900°C in presence of air. Following changes takes place during
    roasting.

    Zinc sulphide is oxidized into its oxide.


    2ZnS + 3O2 → 2ZnO + 2SO2
    Volatile impurities are removed.

    4. Reduction
    Zinc oxide formed after roasting can be reduced by the vertical retort process. In this process,
    roasted ore is mixed with coke in the ratio of 2:1. The retort is heated by burning the producer gas
    (CO + N2) at around 1400°C. On doing so, ZnO gets reduced to Zn by coke (C) as:

    ZnO + C → Zn + CO
    The zinc vapours and carbon monoxide gas are carried in the condenser by the mild current of
    producer gas from the bottom of the furnace. Zinc obtained in the condenser is known as spelter
    zinc.

    ( e & be )
    pe
    !

    m N

    Fig: Vertical Retort Process

    5. Purification or refining of Zinc


    i. Distillation: The zinc spelter is subjected to distillation at 1000°C where impurities like iron
    (b.pt.= 3000°C) and lead (b.pt.= 1620°C) are left behind. Zinc (b.pt.=800°C) and cadmium
    (b.pt.=765°C) are collected as distillate. The distillate is distilled again at 800°C where cadmium is
    distilled off and zinc is left behind. This zinc is 99% pure.

    ii. Electrolysis: The impure zinc is taken as anode and a thin sheet of pure zinc is taken as a
    cathode in a large tank. Acidified ZnSO4 solution is taken as an electrolyte. On electrolysis, the
    anode dissolves and is deposited as pure zinc in the cathode.

    ZnSO4(aq) ⇌ Zn++ + SO4

    At anode : Zn(s)→ Zn++ + 2e−


    Impure

    At cathode : Zn++ + 2e → Zn
    Pure

    This obtained zinc is 99.5% pure.

    (https://sajhanotes.com )

    Fig: Electrolytic cell

    Physical properties
    1. It is blueish white solid when pure but tarnishes to grey when exposed to moist air.
    2. It is good conductor of heat and electricity.
    3. It melts at 420°C and boils at 907°C.
    4. It is malleable and ductile at 100-150°C and brittle at 200°C.

    Chemical properties
    1. Action of air: Zinc is not affected by dry air but gets tarnished when exposed to moist air.

    & e
    e
    !

    united-steel.com OPE

    2
    2Z n + H 2O + O2 + C O2 → Z nC O3.Z n(OH )
    Basic zinc carbonate

    Basic zinc carbonate

    When zinc is heated with air at 500°C, it burns with blueish white flame giving white woolly (dense
    white smoke) zinc oxide called philosopher’s wool or pompholyx.

    2Zn + O2 l
    2 2zno
    2. Action with acids: Zinc lies above hydrogen (in the electrochemical series. Therefore, it produces
    H2 gas from dilute, mineral and non-oxidizing acid. It shows amphoteric nature hence, it reacts
    with acid as well as the base.
    1. Action with H2SO4: Zn + 2H2SO4 (conc)→ ZnSO4+ SO2+ 2H2O >>> Zn + 2H2SO4dil c → ZnSO4+ H2

    2. Action with HCl

    Zn + HCl→ ZnCl2+ H2dil. or conc.

    3. Action with HNO3

    3. Action with alkali

    Zn + 2NaOH → Na2ZnO2 + H2
    Sodium zincate

    4. Displacement reactions: Zinc can displace less reactive metal from its salts.
    Zn + CuSO4→ ZnSO4+ Cu
    Zn + 2AgNO3 → Zn(NO3)2+ 2Ag

    Uses of zinc
    1. It is used for making alloys.
    2. It is used as a reducing and lab reagent.
    3. It is used in the galvanization of iron.
    4. It is used to prepare hydrogen gas.*The process of depositing a thin layer of zinc over the surface of
    iron is called galvanization.

    Compound of zinc
    A. White vitriol: ZnSO4.7H2O Preparation
    i. From Zn, ZnO, ZnCO3, Zn(OH)2 with dil.H2SO4
    Zn + H2SO4 → ZnSO4+ H2
    ZnO + H2SO4→ ZnSO4+ H2O
    ZnCO3+ H2SO4 → ZnSO4+ H2O + CO2
    Zn(OH)2+ H2SO4→ ZnSO4+ 2H2O
    crystallization
    ii . From ZnS ZnSO4(aq.) ZnSO4.7H2O

    ii. below 800°C


    ZnS + 2O2 ZnSO4

    Physical properties
    It is a white crystalline solid.
    It is efflorescent and loses water when exposed to air.
    It is highly soluble in water. Chemical
    properties
    i. Action of heat ii.

    Action of NaOH

    ZnSO4+ 2NaOH → Zn(OH)2+ Na2SO4


    Zn(OH)2+ 2NaOH→ Na2ZnO2+ 2H2O

    iii. Action with barium sulphide

    ZnSO4+ BaS → ZnS.BaSO4


    Lithopone
    (white pigment)

    iv. Formation of double salt -------->>>> K2SO4+ ZnSO4+ 6H2O → K2SO4.ZnSO4.6 H2O
    Double salt

    v. Action with potassium ferrocyanide

    2ZnSO4+ K4[ Fe(CN)6] → Zn2[ Fe(CN)6] + K2SO4


    Zinc ferrocyanide (white ppt.)

    Uses
    Used as electrolyte.
    Used as an eye lotion.
    Used to check bleeding.
    Used to prepare lithopone, a white pigment.
    *Rinman’s green: ZnO.CoO

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