Notes (Chapter # 18) Chemical Industries

 

UNIT# 18

CHEMICAL INDUSTRIES

 

Q#	Question	Year
Q# 01	How is caustic soda prepared by Castner Kellner cell?	[2013]
Q# 02	Write note on Soap.	[2017][2016][2013] [2011][2010]
Q# 03	Write note on Plastic.	[2016][2011][2009]
Q# 04	Write note on Polish.	[2015]
Q# 05	Write note on Varnish.	[2015]
Q# 06	Write note on Paint.	[2015]
Q# 07	Explain various methods of food preservation.	[2018][2017][2013]
Q# 08	Explain Ammonia Solvay process.	[2016][2014][2011] [2009][2008]
Q# 09	Describe the causes of food spoilage.	[2013] [2017]
Q# 10	Write chemical formulae for soda ash.	[2014]
Q# 11	Write chemical formulae for caustic soda.	[2014] [2012] [2010]
Q# 12	Write chemical formulae for baking soda.	[2014] [2012] [2010]
Q# 13	Write chemical formulae for washing soda.	[2012] [2010]
Q# 14	Write chemical formulae for sodium carbonate.	[2015]
Q# 15	Write chemical formulae for copper sulphate.	[2015]
Q# 16	Write chemical formulae for Magnesium sulphate.	[2015]
Q# 17	Write balanced chemical reaction between the zinc and the following ·         O2 ·         Cl2 ·         CHI ·         NaOH ·        S	[2015]

Q. Describe the construction and working of Castner Kellner cell. Also write the production of NaOH.

CASTNER KELLNER CELL [Production of NaOH]

PRINCIPLE

NaOH is prepared by the electrolysis of Brine (aqueous solution of NaCl) in Castner Kellner Cell.

 

CONCENTRATION OF BRINE

25% mass/ mass

 

CONSTRUCTION OF CASTNER KELLNER CELL

It is a rectangular tank of steel

Inside of tank is lined with ‘ebonite’

Anode is made of titanium

Flowing layer of mercury (Hg) at the bottom of tank serves as cathode

 

PROCEDURE

IONIZATION OF NaCl

2NaCl                        ⟶       2Na⁺ + 2Cl^-

When electric current is passed through brine, +ve and –ve ions migrate towards their respective electrodes. Na⁺ ions are discharged at mercury cathode. The sodium deposited at mercury form Sodium Amalgam. The produced Chlorine at the anode is removed from the top of the cell.

 

REACTION AT CATHODE

2Na⁺ + 2e^-    ⟶       2Na

Na forms amalgam

Na + Hg        ⟶       Na/Hg

Na⁺ ions are discharged in preference to H⁺ ions due to high over voltage.

Na⁺ / Na EP= -2.71 V

H⁺/ H EP= 0.00 V

 

REACTION AT ANODE

2Cl^-                ⟶       Cl₂ + 2e^-

 

 

FORMATION OF NaOH

Amalgam shifts to another chamber called ‘denuder’, where it is treated with water to produce NaOH.

2Na/Hg + 2H₂O     ⟶       2NaOH + H₂+ 2Hg

 

ADVANTAGES OF CASNTER KELLNER CELL

·        Obtained NaOH is highly pure

·        Process is very efficient

·        Possible reaction between NaOH and Cl₂ is avoided because NaOH is obtained in separated chamber

 

DISADVANTAGES OF CASTNER KELLNER CELL

·        High electricity consumption

·        Environmental pollution due to escape of Hg vapors

Q. Write chemical properties of sodium hydroxide.

CHEMICAL PROPERTIES OF SODIUM HYDROXIDE

1)   Reaction with acids

For the production of salts, sodium hydroxide can be treated with sulphuric acid, hydrochloric acid, nitric acid.

2NaOH + H₂SO₄     ⟶       Na₂SO₄ + H₂O

NaOH + HCl            ⟶       NaCl + H₂O

NaOH + HNO₃        ⟶       NaNO₃ + H₂O

2)   Reaction with metals

Sodium hydroxide reacts with certain metals like zinc, tin aluminium

2NaOH + Zn                        ⟶       Na₂ZnO₂ + H₂

2NaOH + Sn                        ⟶       Na₂SnO₂ + H₂

2NaOH + Al + 2H₂O         ⟶       2NaAlO₂ + 3H₂

3)   Reaction with carbon di oxide

It reacts with carbon di oxide to produce sodium carbonate and water.

2NaOH + CO₂                     ⟶       Na₂CO₃ + H₂O

4)   Reaction with chlorine gas

The reaction of sodium hydroxide with chlorine gas results in the formation of sodium salt of oxy acids.

2NaOH + Cl₂                       ⟶       NaOCl + NaCl + H₂O

Q. Write physical properties of sodium hydroxide.

PHYSICAL PROPERTIES OF SODIUM HYDROXIDE

·        It is highly insoluble in water

·        It produces high amount of heat

·        Its melting point is 318⁰ C

·        Its density is 2.13 gm/ml

 

Q. Give the industrial preparation of Sodium carbonate.

INDUSTRIAL PREPARATION OF SODIUM CARBONATE

AMMONIA SOLVAY PROCESS OR AMMONIUM SODA PROCESS

Industrially, sodium carbonate is produced by Ammonia Solvay process

 

RAW MATERIALS

The raw materials which are needed for the production of Sodium carbonate are given below:

·        Sodium chloride

·        CO₂

·        NH₄Cl

·        CaCO₃

 

PROCEDURE

At first stage, a saturated solution of sodium chloride is prepared which is also known as Brine.

Brine is the 28% m/m solution of NaCl

Following are the steps of the industry:

 

AMMONIATION OF BRINE

In this stage, saturated solution of NaCl i.e. brine is allowed to flow down from ammoniating tower. The ammoniated tower is fitted with mushroom shaped baffles which are designed to control the flow of brine and ensure the proper mixing and saturation of ammonia.

 

CARBONATION OF AMMINIATED TOWER

In this step, ammoniated brine is allowed to trickle down a carbonating tower called ‘Solvay tower’. Here, brine is fixed with carbon di oxide gas.

CaCO₃                        ⟶       CaO + CO₂

CO₂ reacts with ammonia to form ammonium carbonate

2NH₃ + CO₂ + H₂O            ⟶       (NH₄)₂CO₃

Ammonium carbonate further reacts with CO₂ to form ammonium bi carbonate

(NH₄)₂CO₃ + CO₂ + H₂O  ⟶       2NH₄HCO₃

Ammonium bi carbonate then reacts with NaCl to form Sodium bi carbonate.

NH₄HCO₃ + NaCl   ⟶       NaHCO₃ + NH₄Cl

Due to the exothermic nature of the above reactions, solubility of NaHCO3 increases. To oppose this effect, lower part of Solvay tower is cooled first, precipitate of NaHCO₃ are separated by vacuum filtration and then washed to remove ammonium salts.

 

CONVERSION OF NaHCO₃ TO Na₂CO₃

Sodium bicarbonate is heated in rotary furnace called ‘Calciner’ to produce anhydrous sodium carbonate or soda ash. Carbon di oxide is re-circulated to carbonation tower.

2 NaHCO₃    ⟶       Na₂CO₃ + CO₂ + H₂O

 

RECOVERY OF AMMONIA

The CaO which obtained from the heating of CaCO₃ is treated with water to form Ca(OH)₂

CaO + H₂O   ⟶       Ca(OH)₂

Quick lime is heated with NH₄Cl to form NH₃ and CaCl₂ (by product).

2 NH₄Cl + Ca(OH)₂           ⟶       CaCl₂ + 2NH₃ + 2H₂O

Ammonia is used again in this process.

 

Q. Give the physical properties of Sodium bi carbonate.

PHYSICAL PROPERTIES OF SODIUM BI CARBONATE

·        It is bitter in taste

·        Sparingly soluble in water

·        It is white crystalline compound

·        Its density is 2.11 gm/ ml

 

 

 

Q. Give the chemical properties of Sodium bi carbonate.

CHEMICAL PROPERTIES OF SODIUM BI CARBONATE

 

1)   Reaction with acids

Sodium bi carbonate loses carbon di oxide and water to give sodium carbonate on heating.

NaHCO₃ + HCl        ⟶       NaCl + H₂O + CO₂

 

2)   Action of heat

Sodium bicarbonate loses carbon dioxide and water to give sodium carbonate on heating.

2NaHCO₃                 ⟶       Na₂CO₃ + H₂O + CO₂

 

Q. Give the uses of Sodium bi carbonate.

 

USES OF SODIUM BICARBONATE

·        It is used in the preparation of effervescent drinks.

·        It is used in fire extinguishers.

·        It is used in the textile, tanning, paper, ceramics industries.

·        It is used in medicine as antacid to neutralize the acids.

 

Q. Give the physical properties of Sodium carbonate.

 

PHYSICAL PROPERTIES OF SODIUM CARBONATE

·        It is highly soluble in water

·        Sodium carbonate (Na₂CO₃) is an odorless, grayish white hygroscopic powder.

·        The melting point of Sodium carbonate is 1,564°F (851°C)

·        Density of sodium carbonate 2.53 g/cm³

·        It is soluble in water.

·        The water solution of soda ash has a basic pH and a strong alkaline taste. If it is placed in a slightly acidic solution, it decomposes and forms bubbles. This effect, called effervescence

·        It is used as cleaning agent in soap and detergents.

 

Q. Give the chemical properties of Sodium carbonate.

 

CHEMICAL PROPERTIES OF SODIUM CARBONATE

PRODUCTION OF SALTS

Sodium carbonate can be decomposed to produce salts

Na₂CO₃ + 2HCl       ⟶       2NaCl + H₂O + CO₂

Q. Write note on Paints.

PAINTS

Paint is defined as a mixture of pigments and binding medium which can be spread to a dry thin film to decorated or protect a surface.

There are two different types of paint:

·        Oil Paints

·        Water Paints

OIL PAINTS

1.     The composition of oil paint is linseed oil, a timer a pigment and a dryer.

2.     These types of paints are applied over wooden or iron surfaces.

3.     They are usually known as enemas.

 

 WATER PAINTS

1.     Water paints are compound of emulsion of hydrocarbons, butadiene, styrene, polymers polyvinyl acetate or acrylic resin in water.

2.     These are used over walls, especially interior ones.

3.      They are usually called as distemper and plastic emulsion.

 

Q. Write note on Soap.

SOAP

The salts of sodium and potassium of fatty acids are called soaps.

SAPONIFICATION

Chemically, the preparation of soap is known as Saponification.

In this process, tristerin (stearic acid) reacts with caustic soda in order to produce soap. Glycerol is also produced as by product.

CH₂O₂CC₁₇H₃₅                                                        CH2OH

CHO₂CC₁₇H₃₅ + 3NaOH              ⟶                   CHOH + 3C₁₇H₃₅CO₂Na

CH₂O₂CC₁₇H₃₅                                                                          CH₂OH

 

TYPES OF SOAPS

On the basis of function, soaps are industrially designed for various applications, in which few are describing below.

·        Toilet soap

·        Kitchen soap

·        Laundry soap

·        Shaving soap

 

 

 

TOILET SOAP

The chemical composition of Toilet soap is 80% to 90% tallow oil and 10% to 20% coconut oil.

The toilet soap is used for

 

KITCHEN SOAP

Kitchen soap is ordinarily prepared from sand and washing soda. Such soaps are used for washing and cleaning utensils.

 

LAUNDRY SOAP

Laundry soap is prepared by

Laundry soap is used in washing clothes.

 

SHAVING SOAPS

The shaving soaps are prepared by the

These soaps are used for shaving

 

FUNCTION OF SOAPS

·        Soaps are used for dirt remover

·        Soaps are used for washing

·        Soaps are used for shaving

 

Q. Write note on Detergents.

DETERGENTS

The cleansing agents used for cleaning a solid surface are called detergents. The detergents consists of two parts, a hydrocarbon and a sulphonate (-SO₃^-2). Or sulphate (OSO₃^-2) group. The molecules are made usable by converting them into a water soluble sodium salts.

The detergents are closely related to soap and are used for household laundries.

 

FUNCTIONS OF DETERGENTS

·        Detergents produce their function well in hard water.

·        Detergent removes dirt very easily.

·        Large variety of detergents are used as washing powders ad washing liquids.

 

Q. Write note on Varnishes.

VARNISHES

Varnishes are colloidal without pigments. They dry by evaporation, oxidation and polymerization.

COMPOSITION OF VARNISHES

1.     Hard dark amber gun 20 parts.

2.     China wood oil 3 parts.

3.     Linseed oil 2 parts.

4.     Sprint 7 parts.

 

PREPRATION OF VARNISHES

1.     Amber gun is heated to temperature of 650 ⁰C in an iron kettle.

2.     It is then cooled 500^oC and china wood oil is added.

3.     The mixture again heated to 560^oC and linseed oil is added.

4.     It is cooled to room temperature and sprint is added. This varnish will dry to touch in about 4 hours and hard in about 8 hours.

 

Q. Write note on Polish.

POLISH

A protective layer applied on the surface for the sake of their protection is known as polish. These applied to shoes, furniture, cars, muter cycles, floors of house etc.

SHOE POLISH

Generally black and brown shoes polishes are largely used for the protection of shoes against water and weather.

 

COMPOSITION OF BLACK SHOE POLISH

1.     Powdered animal charcoal

2.     Bees wax

3.     Carnauba wax

4.     Turpentine oil

5.     Nigrosine oil

6.     Sodium hydroxide

7.     Soap

 

Q. Write note on Plastics.

PLASTICS

Plastics are one of the types of polymers. The compounds build up of a large number of smaller molecules that have reached wit hone another are called polymers.

Polymers may be natural or synthesized. Plastics are synthetic polymers.

The two main kind of plastics are:

a.      Thermoplastic

b.     Thermosetting plastics

 

THERMOPLASTICS

Synthetic resins formed by polymerization are known as thermoplastics. They softens on heating and hardens on cooling. The repetition of process does not affect the properties of these types of plastics. They can easily be moulded into different shapes.

Best examples of thermoplastics are cellulose nitrate, cellulose acetate and vinyl polymers.

 

THERMOSETTING PLASTICS

The plastics which can be heated only once are called thermosetting plastics. The process cannot be repeated as they soften on reheating.

Best examples of thermosetting plastics are phenol, formaldehyde, epoxy resins.

 

Polyvinyl chloride

It is a polymer from vinyl chloride (chloromethane).

 

Q. Write note on Ink.

INK

Inks are the deeply colored liquid of venial composition used for writing or printing. They contain a protective substance gum Arabic to make them more durable.

TYPES OF INK

1.     Black ink

2.     Blue ink

3.     Marking ink

4.     Red ink

5.     Printing ink

6.     Type writing ink

7.     Blue black ink

8.     Royal blue ink

9.     Stamp pad ink

 

Q. What is food spoilage? Write causes of food spoilage.

FOOD SPOILAGE

Food cannot last forever food weather fruits, vegetables or cereal grains begin to deteriorate once they are harvested. Similarly meat begins to deteriorate soon after slaughter of the animal.

 

CAUSES

There are different factor which causes food spoilage.

 

a)   MOISTURE

The agriculture product if exposed in higher humidity or in moisture begins to decay due to the growth of molds and bacteria.

 

b)   MICROBIAL ACTIVITIES

The food is also spoiled by biological attack of pests, microbes and other pathogens.

 

c)    CHEMICAL CHANGES

Some food enzyme also cause the food spoilage yeast molds and bacteria also produce enzyme which containment the food products.

 

Q. What is food preservation? What are different methods of food preservation? Briefly describe each.

FOOD PRESERVATION

The food needs to be stored and supplied to distant areas. There are different methods of preservation of foods.

 

a)   REMOVAL OF MOISTURE

In this process to preserve food by drying process moisture is removed milk, coffee, tea and some vegetable, fruit, meat and eggs are dried to preserve. Dried foods are easy to store and transport.

 

b)   ADDITION OF SALT AND SUGAR

To increase the shelf life of many sausages sugar and salt are added to them. The sugar and salt bind the water to prohibit the growth of micro-organism. In this way food is preserved from spoiling.

 

c)    TEMPERETURE CONTROL

Temperature control is another way to preserve the food against the micro-organisms’ growth. Refrigeration or gracing of food lowers the envoi mental temperature for the growth of many harmful organisms.

 

d)   STORAGE

Food is stored and preserved for a long period is done by two process canning and radiation.

 

e)   CANNING

Canning is another method for food preservation. In this method food is sealed into air tight containers. The raw food is packed into the container sealed and the whole package is then treated with heat and steam pressure used to cook the food and sterilize the food.

 

f)     RADIATION

Radiation can be used to preserve food such as heat potato and onion etc. in this process radiation is passing through the food. The radiation is compensating of alpha, beta and gamma. The process is known as radiation and leaves no residual radioactivity in the food.

 

g)   CHEMICAL ADDITION

i.            Sometime to preserve food certain chemical substances are added in small proportion in the food. These chemical are salt of calcium, magnesium, potassium and sodium.

ii.            Sodium sulphide and potassium meta-sulphide are used to prevent the growth of micro-organism.

iii.            Sodium dehydrogenate phosphate is incorporated to improve the texture.

iv.            Magnesium hydroxide reduces the acidity of food.

v.            Addition of common salt preserves meat and fish items.

vi.            Dry fruits, jams and jellies are preserved by the addition of sculpture die-oxide or salts of sulphuric acid.

Q. Write the chemical formulae of each given chemicals.

Chemical naming	Chemical Formulae
Soda ash	Na2CO3
Caustic soda	NaOH
Washing soda	Na2CO3.10H2O
Sodium carbonate	Na2CO3
Copper sulphate	CuSO4
Magnesium sulphate	MgSO4

Choose the correct option for each of the following statement.

i.                   NaOH is prepared at large scale by the following method.

a.      Electrolysis

b.     Hydrolysis

c.      Saponification

d.     Rancidification

ii.                CO₂ and NaOH react to give:

a.      Sodium carbonate and water

b.     Sodium carbonate only

c.      Sodium metal and water

d.     Sodium and carbon monoxide

iii.             The type of plastic that can be heated only once:

a.      Thermoplastic

b.     Thermosetting plastic

c.      Cellulose nitrate

d.     Epoxy resin

iv.               Which of the following constituents of shoe polish used to provide shining to the shoes?

a.      Bees wax

b.     Pearl ash

c.      NaOH

d.     Soap

v.                 Varnishes are used:

a.      With pigments

b.     Without pigments

c.      Without resins

d.     None of these

vi.              Cameras, radios, telephone sets etc. are prepared from:

a.      Bakelite

b.     PVC

c.      Cellulose nitrate

d.     Polyethene