P Block Elements
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In the preparation of H2SO4 by Contact Process, why is SO3 not absorbed directly in water to form H2SO4 ?
In the preparation of H2SO4 by Contact Process, why is SO3 not absorbed directly in water to form H2SO4 ?
This is a short answer type question as classified in NCERT Exemplar
SO3 generates a dense fog of sulphuric acid that does not condense quickly, it is not absorbed directly in water to form H2SO4.
Upvote 
On heating compound (A) gives a gas (B) which is a constituent of air. This gas when treated with 3 mol of hydrogen (H2) in the presence of a catalyst gives another gas (C) which is basic in nature. Gas C on further oxidation in moist condition gives a compound (D) which is a part of acid rain. Identify compounds (A) to (D) also give necessary equations of all the steps involved.
On heating compound (A) gives a gas (B) which is a constituent of air. This gas when treated with 3 mol of hydrogen (H2) in the presence of a catalyst gives another gas (C) which is basic in nature. Gas C on further oxidation in moist condition gives a compound (D) which is a part of acid rain. Identify compounds (A) to (D) also give necessary equations of all the steps involved.
This is a long answer type question as classified in NCERT Exemplar
A = NH4NO2
B = N2
C = NH3
D = HNO3
(i) NH4NO2→N2 + 2H2O
(ii) N2 + 3H2→2NH3
(iii) 4NH3 + 5O2→4NO + 6H2O
4NO + O2→4NO2
3NO2 + H2O→2HNO3 + NO
Upvote On heating lead (II) nitrate gives a brown gas “A”. The gas “A” on cooling changes to colourless solid “B”. Solid “B” on heating with NO changes to a blue solid ‘C’. Identify ‘A’, ‘B’ and ‘C’ and write reactions involved and draw the structures of ‘B’ and ‘C’.
On heating lead (II) nitrate gives a brown gas “A”. The gas “A” on cooling changes to colourless solid “B”. Solid “B” on heating with NO changes to a blue solid ‘C’. Identify ‘A’, ‘B’ and ‘C’ and write reactions involved and draw the structures of ‘B’ and ‘C’.
This is a long answer type question as classified in NCERT Exemplar
Here, ‘A’ is NO2 (Nitrogen dioxide)
‘B’ is N2O4 (dinitrogen tetraoxide)
‘C’ is N2O3 (dinitrogen trioxide)
A brown gas is produced when lead nitrate (II) is heated
2Pb (NO3)2 
2PbO + 4NO2 + O2
2NO2 
N2O
Upvote An amorphous solid “A” burns in air to form a gas “B” which turns lime water milky. The gas is also produced as a by-product during roasting of sulphide ore. This gas decolourises acidified aqueous KMnO4 solution and reduces Fe3+ to Fe2+ . Identify the solid “A” and the gas “B” and write the reactions involved.
An amorphous solid “A” burns in air to form a gas “B” which turns lime water milky. The gas is also produced as a by-product during roasting of sulphide ore. This gas decolourises acidified aqueous KMnO4 solution and reduces Fe3+ to Fe2+ . Identify the solid “A” and the gas “B” and write the reactions involved.
This is a long answer type question as classified in NCERT Exemplar
‘A’ is S8 ‘B’ is SO2 gas
S8 + 8O2 
8SO2
2MnO4 – + 5SO2 + 2H2O → 5 SO42– + 4H+ + 2Mn2+
(violet) &nbs
Upvote 7.70 Arrange the following in the order of property indicated for each set: (i) F2 , Cl2 , Br2 , I2 - increasing bond dissociation enthalpy. (ii) HF, HCl, HBr, HI - increasing acid strength. (iii) NH3, PH3, AsH3, SbH3, BiH3 – increasing base strength.
7.70 Arrange the following in the order of property indicated for each set: (i) F2 , Cl2 , Br2 , I2 - increasing bond dissociation enthalpy. (ii) HF, HCl, HBr, HI - increasing acid strength. (iii) NH3, PH3, AsH3, SbH3, BiH3 – increasing base strength.
7.70
As Bond dissociation energy generally decreases on moving down the group as the atomic size of the element increases. However, among halogens, the bond dissociation energy of F2 is lower than that of Cl2 and F2 due to the small atomic size of
Thus increasing order for bond dissociation energy amo
Upvote 7.69
(i) XeO3 can be produced by hydrolysis of XeF4 and XeF6 under controlled pH of the medium in which reaction is taking place as shown below:
6XeF4 + 12H2O → 4Xe + 2XeO3 + 24HF + 3O2
XeF6 + 3H2O → XeO3 + 6HF
(ii) XeOF4 can be obtained on partial hydrolysis of XeF6 as shown below:
XeF6 + H2O → XeOF4
Upvote 7.68 With what neutral molecule is ClO– isoelectronic? Is that molecule a Lewis base?
7.68 With what neutral molecule is ClO– isoelectronic? Is that molecule a Lewis base?
7.68
ClO- isisoelectronic to ClF as both the compounds contain 26 electrons in all. ClO- : 17+8+1 = 26
ClF : 17+9 = 26
Yes, ClF Molecule is a Lewis base as it accepts electrons from F to form ClF3.
Upvote 7.67 How are xenon fluorides XeF2, XeF4 and XeF6 obtained?
7.67 How are xenon fluorides XeF2, XeF4 and XeF6 obtained?
7.33
Xe and F2 combine under different conditions to produce XeF2, XeF4, XeF6 as follows:
Ratio | Temperature & Pressure Condition | Reaction |
Excess | at {673K,1bar} | Xe (g) + F2 (g) → XeF2 (s) |
1:5 ratio | at {873K,7bar} | Xe (g) + 2F2 (g) → XeF4 (s) |
1:20 ratio | at {573K,60-70bar} | Xe (g) + 3F2 (g) → XeF6 (s) |
Upvote 7.66 Write balanced equations for the following: (i) NaCl is heated with sulphuric acid in the presence of MnO2. (ii) Chlorine gas is passed into a solution of NaI in water.
7.66 Write balanced equations for the following: (i) NaCl is heated with sulphuric acid in the presence of MnO2. (ii) Chlorine gas is passed into a solution of NaI in water.
7.66
4NaCl + MnO2 + 4H2SO4 MnCl2 + 4NaHSO4 + 2H2O + Cl2
Manganese (IV) oxide reacts with sodium chloride and sulfuric acid to produce manganese (II) chloride, chlorine, sodium bisulfate and water.
This reaction takes place at a temperature near 100°C.
Cl2 + NaI 2NaCl + I2
Chlorine reacts with
Upvote 7.65 What are the oxidation states of phosphorus in the following: (i) H3PO3 (ii) PCl3 (iii) Ca3P2 (iv) Na3PO4 (v) POF3?
7.65 What are the oxidation states of phosphorus in the following: (i) H3PO3 (ii) PCl3 (iii) Ca3P2 (iv) Na3PO4 (v) POF3?
7.65
Let the oxidation state of P be x:
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