Draw the structure of H 3 PO 2 and account for its reducing behaviour on the basis of its structure.

Hypophosphorus acid ( H 3 PO 2 ) is an oxoacid of phosphorous, which contains one P = O , one P - OH and two P - H bonds. So, due to the presence of two P - H bonds, it behaves as a strong reducing agent. The structure is as shown below:

H - P - H bond angle in PH 3 is less than H - N - H bond angle in NH 3 . Give reason.

In ammonia molecule, there are three bonding pairs and one lone pair in the outermost shell of nitrogen atom. The repulsion between lone pair and a bond pair of electrons always exceeds to that of two bond pairs. Thus, the bond angles are reduced from 109 . 5 ° to 107 . 5 ° . In PH 3 molecule, the bond pairs of electrons are much further away from the central atom due to its larger size. Thus, the lone pair causes even greater distortion in PH 3 . So the bond angle decrease to 91 ° . Therefore, the bond angle of PH 3 molecule is lesser than that in NH 3 molecule.

Write the manufacture of HNO 3 by Ostwald’s process with stepwise equations.

The steps involved in the manufacture of nitric acid by Ostwald's process are given below: (i) Catalytic oxidation of ammonia: Ammonia is oxidised by atmospheric air by heating at 500 K and 9 bar pressure in the presence of platinum-rhodium gauze catalyst, it forms nitric oxide. 4 NH 3 g + 5 O 2 g → 500 K / 9 bar Pt - Rh 4 NO g + 6 H 2 O l (ii) Oxidation of nitric oxide: Nitric oxide combines with oxygen to form nitrogen dioxide. 2 NO g + O 2 g → 2 NO 2 g (iii) Absorption of nitrogen dioxide in water: Nitrogen dioxide dissolves in water to give nitric acid and nitric oxide gas. 3 NO 2 g + H 2 O l → 2 HNO 3 aq + NO g

Give the structure of PCl 5 molecule in gaseous or liquid state. Are all the P - Cl bonds equivalent? Justify your answer.

Phosphorous pentachloride has a trigonal bipyramidal structure due to sp 3 d -hybridisation of phosphorous atom, in gaseous and liquid phases. The structure is as shown below: All the P - Cl bonds in PCl 5 molecule are not equivalent. The three equatorial P - Cl bonds are equivalent, while the two axial bonds are longer than equatorial bonds. This is due to the axial bond pairs suffer more repulsion as compared to equatorial bond pairs.

Fluorine has only - 1 oxidation state, but other halogens have oxidation states as + 1 , + 3 , + 5 and + 7 also. Give reasons.

All halogens exhibit - 1 oxidation state, because they gain an electron to complete their octet structure. Chlorine, bromine and iodine show + 1 , + 3 , + 5 and + 7 oxidation states in different excited states, but fluorine cannot exhibit the higher oxidation states due to the absence of d -subshell, and inability to expand octet structure. Fluorine cannot show + 1 oxidation state also due to high electronegativity.

Draw the structure of HClO 4 .

Perchloric acid ( HClO 4 ) is an oxoacid of chlorine, which contains one hydroxyl group attached to the central chlorine atom, and three chlorine to oxygen double bonds. Therefore, the structure of HClO 4 can be written as given below:

Dry chlorine gas does not act as a bleaching agent. Give reason.

Chlorine acts as a bleaching agent only in the presence of moisture. Chlorine reacts with water to form hydrogen chloride and nascent oxygen, due to nascent oxygen, chlorine bleaches by oxidation. Therefore, dry chlorine gas does not act as a bleaching agent. Cl 2 + H 2 O → 2 HCl + O

Which state of sulphur exhibits paramagnetism and why?

Under ordinary conditions sulphur exists as S 8 in solid state. In vapour state sulphur partly exists as S 2 molecule, and it has two unpaired electrons in the antibonding π * orbitals like O 2 . Hence, in vapour state sulphur exhibits paramagnetism.

E M B I B E

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR CHEMISTRY>Chapter -1 - The p-Block Elements>Meghalaya Board-2020>Q 26

EASY

12th Meghalaya Board

IMPORTANT

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Mention the theory and conditions required to maximise the yield of ammonia for its synthesis by Haber’s process.

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