3 Marks Question

Question 13 Marks

Draw the structure of the following:
(i) $ H_{3}PO_{4} $, (ii) $ H_{3}PO_{3} $, (iii) $ H_{3}PO_{2} $, (iv) $ H_{4}P_{2}O_{7} $, (v) $ (HPO_{3})_{3} $

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Question 23 Marks

Give the principle of the manufacture of nitric acid from ammonia?

Answer

In this process a mixture of ammonia and air (or oxygen) is passed over platinum gauze catalyst or rhodium- platinum alloy. Ammonia is oxidised to nitric oxide.
$4 NH _3+ SO _2 \xrightarrow[1070 K]{ PT } 6 H _2 O +4 NO$
Nitric oxide is allowed to cool and mixed with oxygen or air to convert it into nitrogen dioxide.
$2 NO + O _2 \longrightarrow 2 NO _2$
Nitrogen dioxide so form is dissolve in water and nitric acid is obtained.
$2 NO _2+ H _2 O \longrightarrow HNO _3+ HNO _2$
$3 HNO _2 \longrightarrow HNO _3+2 NO + H _2 O$

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Question 33 Marks

What are main sources of Iodine? How it is extracted from sea weeds?

Answer

Main Sources of Iodine: (i) Sea weeds contain upto $0.5 \%$ of Iodine as NaI and KI .
(ii) Chile salt pitre contain upto $0.2 \%$ of sodium iodate, chile salt pitre contains $NaNO _3$ and $NaIO _3$.
Extraction of Iodine from Sea Weeds : The sea weeds of laminaria family are collected, dried and burnt. The ash left is called kelp. The ash is extracted with hot water which dissolves $Cl ^{-}, CO _3^{2-}, SO _4^{2-}$ and $I ^{-}$of Na and K .
The solution on concentration and cooling separates out $CI ^{-}, CO _3^{2-}$, and $SO _4^{2-}$ of Na and K while iodine remain in solution. The solution is mixed with $MnO _2$ and Conc. $H _2 SO _4$ iron retorts. Iodine is liberated and condensed in series of earthen ware receivers called alludels.
$2 NaI + MnO _2+3 H _2 SO _4 \rightarrow 2 NaHSO _4+ MnSO _4+ H _2 O + I _2$
Pure iodine is obtained by sublimation.

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Question 43 Marks

Give the structures of IF3, CIF5 and IF7.

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