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

    Solution

    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

    Solution

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

    Solution

    iv. HI acid when heated with conc. H2SO4 forms
    A. HIO3

    B. KIO3
    C. I2

    D. KI

    Solution

    v. Ozone layer is depleted by
    A. NO

    B. NO2
    C. NO3

    D. N2O5 

    Solution

    vi. Which of the following occurs in liquid state at room temperature ?
    A. HIO3

    B. HBr
    C. HCl

    D. HF

    Solution

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

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

    D. Only +6

    Solution

    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

    Solution

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

    Solution

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

    B. ClF3
    C. ClF2

    D. Cl2F3

    Solution

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

    B. Cl

    C. Br

    D. F

    Solution

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

    B. ICl
    C. IF5

    D. ClF3

    Solution

    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

    Solution

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

    Solution

    2. Answer the following.

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

    Solution

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

    Solution

    iii. Name two gases which deplete ozone layer.

    Solution

    iv. Give two uses of ClO2

    Solution

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

    Solution

    vi. Write the names of allotropic forms of selenium.

    Solution

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

    Solution

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

    Solution

    ix. Give one example showing reducing property of ozone.

    Solution

    x. Write the reaction of conc. H2SO4 with sugar

    Solution

    xi. Give two uses of chlorine.

    Solution

    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

    Solution

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

    Solution

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

    Solution

    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.

    Solution

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

    Solution

    iii. How is dioxygen prepared in laboratory from KClO3 ?

    Solution

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

    Solution

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

    Solution

    vi. Discuss the structure of sulfure dioxide.

    Solution

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

    Solution

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

    Solution

    ix. How is hydrogen chloride prepared from sodium chloride ?

    Solution

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

    Solution

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

    Solution

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

    Solution

    xiii. Give two uses of HCl.

    Solution

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

    Solution

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

    Solution

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

    Solution

    xvii. How are XeO3 and XeOF4 prepared ?

    Solution

    xviii. Give two uses of neon and argon.

    Solutin

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

    Solution

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

    Solution

    4. Answer the following.

    i. Distinguish between rhombic sulfur and monoclinic sulfur.

    Solution

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

    Solution

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

    Solution

    iv. Describe the manufacturing of H2SO4 by contact process.

    Solution