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12th Standard
Chemistry
Who do soaps not work in hard water?
Name some important categories of food additives.
Give some of the advantages of using food additives.
Write a short note on Antioxidants.
How is Low density polyethene prepared?
Give the structure of melamine formaldehyde resin.
The monomer is capro lactam 
Identify the polymer when the monomer is heated at 533K.
How is Nylon - 6,6 prepared? Give it use.
Give the condensation reaction between urea and formaldehyde. Identify the polymer.
Write the preparation of neoprene and give its use.
How is Buna - N prepared? Give its use.
Identify the polymer and write the reaction involved.
(i) Buta-1,3-diene and styrene in the presence of sodium.
(ii) 3 - hydroxy butanoic acid and 3-hydroxy pentanoic acid.
Give examples for
(i) addition polymer,
(ii) Synthetic rubbers,
(iii) Condensation polymers,
(iv) formaldehyde resins.
Identify the monomers of the following polymers.
(ii) (NH(CH2)6 NHCO (CH2)4 CO)n
(iii) \({ CH }_{ 2 }-\underset { \overset { | }{ Cl } }{ C } =CH-{ CH }_{ 2 })_{ n }\)
State any three advantages of food additives.
Answers
Hard water contains salts of calcium and magnesium. When soaps are dissolved in hard water, these ions displace sodium and potassium from their salts and form insoluble calcium and magnesium salts of fatty acids. These insoluble salts separate as scum, Thus soaps do not work in hard water.
(i) Aroma compounds
(ii) Food colours
(iii) Preservatives
(iv) Stabilizers
(v) Artificial Sweeteners
(vi) Antioxidants
(vii) Buffering substances
(viii) Vitamins and minerals
Advantages of food additives :
(i) Uses of preservatives reduce the product spoilage and extend the shelf-life of food.
(ii) Addition of vitamins and minerals reduces the mall nutrient.
(iii) Flavouring agents enhance the aroma of the food.
(iv) Antioxidants prevent the formation of potentially toxic oxidation products of lipids and other food constituents.
(i) Antioxidants are substances which retard the oxidative deteriorations of food.
(ii) Food containing fats and oils is easily oxidised and turn rancid.
(iii) To prevent the oxidation of the fats and oils, chemical BHT(butylhydroxy toluene), BHA(Butylated hydroxy anisole) are added as food additives.
(iv) They are generally called antioxidants. These materials readily undergo oxidation by reacting with free radicals generated by the oxidation of oils, thereby stop the chain reaction of oxidation of food.
LDPE is formed by heating ethene at 200° to 300°C under oxygen as a catalyst. The reaction follows free radical mechanism. The peroxides formed from oxygen acts as a free radical initiator.
Capro lactam (monomer) on heating at 533K in an inert atmosphere with traces of water gives \(\in \) amino carproic acid which polymerises to give nylon - 6
Nylon - 6,6 can be prepared by mixing equimolar adipic acid and hexamethylene - diamine to form a nylon salt which on heating eliminate a water molecule to form amide bonds.
It is used in textiles, manufacture of cards etc ...
It is formed by the condensation polymerisation of the monomers urea and formaldehyde.
The free radical polymeristion of the monomer, 2-c Woro buta -1,3-diene( chloroprene) gives neoprene.
It is superior to rubber and resistant to chemical action.
Uses: It is used in the manufacture of chemical containers, conveyer belts
It is a co-polymer of acrylonitrile and buta-1,3-diene.
It is used in the manufacture of hoses and tank linings.
(i) It is a co-polymer It is obtained by the polymerisation of buta-Ls-diene and styrene in the ratio 3:1 in the presence of sodium.
(ii) It is the co - polymer of the monomers 3 - hydroxybutanoic acid and 3-hydroxypentanoic acid. In PHBV, the monomer units are joined by ester linkages.
(i) Addition polymer: Polyethene, Polystyrene
(ii) Synthetic rubbers: Butyl rubbers, Buna rubbers
(iii) Condensation polymers: Terylene, glyptal, Nylon 6 6.
(iv) formaldehyde resins: Bakelite, Navolave
Advantages of food additives:
1. Uses of preservatives reduce the product spoilage and extend the shelf-life of food
2. Addition of vitamins and minerals reduces the mall nutrient
3. Flavouring agents enhance the aroma of the food
4. Antioxidants prevent the formation of potentially toxic oxidation products of lipids and other food constituents
