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2 Chemistry -- Heavy Metals: Zinc

What happens when zinc sulfate is treated with excess of caustic potash solution ?

What happens when zinc sulfate is treated with excess of caustic potash solution ?

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Sodium hydroxide reacts with metallic salts to form hydroxides which may be insoluble or dissolve in excess of NaOH to form salts of oxyacids. Some of the hydroxides decompose into insoluble oxides,

Zinc salt  forms insoluble hydroxide with NaOH, which dissolves in excess of NaOH.
ZnSO4​+2NaOH→Zn(OH)2​↓+Na2​SO4​                                        white (insoluble)
Zn(OH)2​+2NaOH→Na2​ZnO2​+2H2​O                                           sodium zincate                                                (soluble)

More questions on Heavy Metals: Zinc

What happens when white vitrol is heated ?


How does zinc react with various concentrations of nitric acid ?

1. When zinc reacts with very dilute nitric acid it produces NH4.NO3.
4Zn + 10HNO3(dilute) 4Zn(NO3)2+ NH4NO3+ 3H2O

2. Zinc reacts with dilute Nitric acid to produce Zinc nitrate, nitric oxide and water
3Zn + 8HNO 3Zn(NO) + 2NO + 4HO

3. Zinc reacts with concentrated Nitric acid to produce Zinc nitrate, nitrogen dioxide and water.
Zn + 4HNO Zn(NO) + 2NO + 2HO

Show that zinc white is an amphoteric substance.

Zinc oxide is amphoteric because it reacts with both acids and bases to form salts.

Reactions:


ZnO + 2HCl ZnCl2 + H2O

(Zinc chloride)



2NaOH + ZnO Na2ZnO2 + H2O

(Sodium zincate)

How does zinc react with various concentrations of nitric acid ?

1. When zinc reacts with very dilute nitric acid it produces NH4.NO3.
4Zn + 10HNO3(dilute) 4Zn(NO3)2+ NH4NO3+ 3H2O

2. Zinc reacts with dilute Nitric acid to produce Zinc nitrate, nitric oxide and water
3Zn + 8HNO 3Zn(NO) + 2NO + 4HO

3. Zinc reacts with concentrated Nitric acid to produce Zinc nitrate, nitrogen dioxide and water.
Zn + 4HNO Zn(NO) + 2NO + 2HO

Define: a) Sphelter Zinc b)Granulated Zinc

a) Sphelter Zinc:

Sphelter Zincis an alloy of equal parts copper and zinc, i.e. a brass, used further for hard soldering and brazing.

Elaborate on: a) Galvanizationb) Sherardizing

a)Galvanization:

The process of thin coating of zinc to the surface of iron sheets to prevent the rusting of iron by opposing the direct contact or iron to the atmosphere or buy forming electrochemical couple.

The galvanization process consists of the three basic steps i.e. surface preparation followed by fluxing and then it undergoes galvanizing. Material is loaded and then immersed in the molten zinc at degrees until the temperature is the same as zinc.

b) Sherardizing:

Sherardizing is the...

List the uses of Zinc.

The uses of Zinc are:

1. It is used for manufacturing like creating roofing materials or makingzinc oxide.

2. It is used for various purposes ranging from sunscreens to solar cells to nuclear reactors.

3. The metal helps in maintaining the balance of enzymes in the human body.

4. It is used as a white pigment for oil-based paints.

5. Zinc sulfide is used for making fluorescent lights, x-ray screens as well as luminous paints

Give the reaction of zinc with acid.

Reaction of Zn with H2SO4 depends on concentration of acid.

  • For dilute acid, zinc sulphate and hydrogen gas at produced.

Zn + H2 SO4 ZnSO4 + H2

  • For concentrated sulphuric acid, zinc sulphate , Sulphur dioxide and water are produced.

Zn + conc. 2 H2SO4 ZnSO4 + SO2 + 2 H2O

Give an account the compounds of Zinc.

Zinc is mainly used as a protective coating for iron and steel (galvanising). It is further used for the production of zinc alloys (e.g. brass), rolled zinc, zinc dust (a pigment and a reducing agent), and zinc compounds (e.g. zinc oxide).

  • Zinc oxide is the industrially most important zinc compound. It is used in rubber (vulcanising, pigment), photocopy paper, chemicals and paints. Other uses are in floor coverings, in glasses, enamels, fabrics, plastics, lubricants, in rayon manufacture, and...

What happens when zinc reacts with concentrated sulphuric acid ?

zinc will react with sulphuric acid forming zinc sulphate dissolved in solution and releasing hydrogen gas.
Zn + conc. 2 H2SO4 ZnSO4 + SO2 + 2 H2O

What does the term electrogalvanization mean ?

It is a process of electroplating a layer of zinc on the surface of steel. This process includes immersing a steel component in a solution containing zinc salts followed by application of electricity to induce electrochemical reaction on top of the steel. This is a method of galvanizing iron to prevent it from rusting.

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