Q27 of 50 Page 1

What are the following substances? Give one example of each.

(i) Food preservatives


(ii) Synthetic detergents


(iii) Antacids


(i) A food preservative is a substance or a chemical which is added to food items to prevent their decomposition by microbial growth or by undesirable chemical changes and to prevent its spoilage. Eg. Sodium benzoate.


(ii) Synthetic detergents are basically the sodium or potassium salts of long chain sulphonic acids (member of the class of organosulphur compounds with the general formula R−S(=O)2−OH, where R is an organic alkyl or aryl group). They don’t precipitate in hard water. e.g. Sodium laurylsulphate.


(iii) Antacids are substances which are used to neutralize the acids produced in stomach. Also it helps in relieving heat burns, indigestions and other problems. E.g. Milk of magnesia.


More from this chapter

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25

State reasons for the following:

(i) pKb value for aniline is more than that for methylamine.


(ii) Ethylamine is soluble in water whereas aniline is not soluble in water.


(iii) Primary amines have higher boiling points than tertiary amines.


 26

Draw the structures of the monomers of the following polymers:

(i) Polythene


(ii) PVC


(iii) Teflon


 28

(a) What type of a battery is lead storage battery? Write the anode and cathode reactions and the overall cell reaction occurring in the operation of a lead storage battery.

(b) Calculate the potential for half-cell containing 0.10 M K2Cr2O7 (aq), 0.20 M Cr3+ (aq) and 1.0 x 10-4 M H+ (aq) The half-cell reaction is and the standard electrode potential is given as E° = 1.33 V


OR


(a) How many moles of mercury will be produced by electrolyzing 1.0 M Hg(NO3)2 solution with a current of 2.00 A for 3 hours? [Hg(NO3)2 = 200.6 g mol–1]


(b) A voltaic cell is set up at 25°C with the following half-cells Al3+ (0.001 M) and Ni2+ (0.50 M). Write an equation for the reaction that occurs when the cell generates an electric current and determine the cell potential.
(Given: E0Ni2+| Ni = -0.25V, E0Al3+|Al = -1.66V) [5]


 29

(a) Draw the structures of the following molecules:
(i) (HPO3)3 [5]

(ii) BrF3


(b) Complete the following chemical equations:


(i)


(ii)


(iii)


OR


(a) What happens when
(i) Chlorine gas is passed through a hot concentrated solution of NaOH?
(ii) Sulphur dioxide gas is passed through an aqueous solution of a Fe(III) salt?


(b) Answer the following :
(i) What is the basicity of H3PO3and why?
(ii)Why does fluorine not play and role of a central atom in interhalogen compounds?
(iii)Why do noble gases have very low boiling points?