chapter 7.  ELEMENTS OF GROUPS 16, 17 AND 18 class 12 chemistry textbook solution

1. Select appropriate answers for the following.

i. Which of the following has highest electron gain enthalpy ?
A. Fluorine

B. Chlorine
C. Bromine

D. Iodine

ii. Hydrides of group 16 are weakly acidic. 
The correct order of acidity is
A. H2O > H2S > H2Se > H2Te
B. H2Te > H2O > H2S > H2Se
C. H2Te > H2Se > H2S > H2O
D. H2Te > H2Se > H2O > H2S

iii. Which of the following element does not show oxidation state of +4 ?
A. O B. S C. Se D. Te

iv. HI acid when heated with conc. H2SO4 forms

C. I2


v. Ozone layer is depleted by

B. NO2
C. NO3

D. N2O5 

vi. Which of the following occurs in liquid state at room temperature ?

B. HBr
C. HCl


vii. In pyrosulfurous acid oxidation state of sulfur is
A. Only +2

B. Only +4
C. +2 and +6

D. Only +6

viii. Stability of interhalogen compounds follows the order
A. BrF > IBr > ICl > ClF > BrCl
B. IBr > BeF > ICl > ClF > BrCl
C. ClF > ICl > IBr > BrCl > BrF
D. ICl > ClF > BrCl > IBr > BrF

ix. BrCl reacts with water to form
A. HBr B. Br2 + Cl2
C. HOBr D. HOBr + HCl

x. Chlorine reacts with excess of fluorine to form.
A. ClF

B. ClF3
C. ClF2

D. Cl2F3

xi. In interhalogen compounds, which of the following halogens is never the central atom.
A. I

B. Cl

C. Br

D. F

xii. Which of the following has one lone pair of electrons ?
A. IF3

B. ICl
C. IF5

D. ClF3

xiii. In which of the following pairs, molecules are paired with their correct shapes ?
A. [I3] : bent
B. BrF5 : trigonal bipyramid
C. ClF3 : trigonal planar
D. [BrF4] : square planar

xiv. Among the known interhalogen compounds, the maximum number of
atoms is
A. 3 B. 6 C. 7 D. 8

2. Answer the following.

i. Write the order of the thermal stability of the hydrides of group 16 elements.

ii. What is the oxidation state of Te in TeO3 ?

iii. Name two gases which deplete ozone layer.

iv. Give two uses of ClO2

v. What is the action of bromine on magnesium metal ?

vi. Write the names of allotropic forms of selenium.

vii. What is the oxidation state of S in H2SO4.

viii. The pKa values of HCl is -7.0 and that of HI is -10.0. Which is the stronger acid ?

ix. Give one example showing reducing property of ozone.

x. Write the reaction of conc. H2SO4 with sugar

xi. Give two uses of chlorine.

xii. Complete the following.
1. ICl3 + H2O …….. + …… + ICl
2. I2 + KClO3 ……. + KIO2
3. BrCl + H2O ……. + HCl
4. Cl2 + ClF3 ……..
5. H2C = CH2 + ICl …….
6. XeF4 + SiO2 ……. + SiF4
7. XeF6 + 6H2O …….. + HF
8. XeOF4 + H2O ……. + HF

xiii. Match the following 
A                                B
XeOF2                    Xenon trioxydifluoride
XeO2F2                 Xenon monooxydifluoride
XeO3F2                Xenon dioxytetrafluoride
XeO2F4                 Xenon dioxydifluoride

xiv. What is the oxidation state of xenon in the following compounds.
XeOF4, XeO3, XeF6, XeF4, XeF2.

3. Answer the following.

i. The first ionisation enthalpies of S, Cl and Ar are 1000, 1256 and 1520 kJ/mol-1, respectively. Explain the observed trend.

ii. “Acidic character of hydrides of group 16 elements increases from H2O to H2Te” Explain.

iii. How is dioxygen prepared in laboratory from KClO3 ?

iv. What happens when
a. Lead sulfide reacts with ozone (O3).
b. Nitric oxide reacts with ozone.

v. Give two chemical reactions to explain oxidizing property of concentrated H2SO4

vi. Discuss the structure of sulfure dioxide.

vii. Fluorine shows only -1 oxidation state while other halogens show -1, +1, +3, +5 and +7 oxidation states. Explain.

viii. What is the action of chlorine on the following
a. Fe b. Excess of NH3

ix. How is hydrogen chloride prepared from sodium chloride ?

x. Draw structures of XeF6, XeO3, XeOF4, XeF2.

xi. What are inter-halogen compounds ? Give two examples

xii. What is the action of hydrochloric acid on the following ?
a. NH3 b. Na2CO3

xiii. Give two uses of HCl.

xiv. Write the names and structural formulae of oxoacids of chlorine

xv. What happens when a. Cl2 reacts with F2 in equal volume at
437 K. b. Br2 reacts with excess of F2.

xvi. How are xenon fluorides XeF2, XeF4 and XeF6 obtained ? Give suitable reactions.

xvii. How are XeO3 and XeOF4 prepared ?

xviii. Give two uses of neon and argon.

xix. Describe the structure of Ozone. Give two uses of ozone.

xx. Explain the trend in following atomic properties of group 16 elements.
i. Atomic radii ii. Ionisation enthalpy
iii. Electronegativity

4. Answer the following.

i. Distinguish between rhombic sulfur and monoclinic sulfur.

ii. Give two reactions showing oxidising property of concentrated H2SO4.

iii. How is SO2 prepared in laboratory from sodium sulfite? Give two physical  properties of SO2.

iv. Describe the manufacturing of H2SO4 by contact process.