AP Inter 2nd Year Chemistry Important Questions Chapter 6(c) Group-17 Elements

Students get through AP Inter 2nd Year Chemistry Important Questions Lesson 6(c) Group-17 Elements which are most likely to be asked in the exam.

AP Inter 2nd Year Chemistry Important Questions Lesson 6(c) Group-17 Elements

Very Short Answer Questions

Question 1.
Interhalogen compounds are more reactive than the constituent halogens except fluorine – Explain.
Answer:
Inter halogen compounds are more reactive than halogens. This is because X – X’ bond in interhalogens is weaker than X — X bond in halogens except F – F bond.

Question 2.
What is the use of ClF₃?
Answer:
ClF₃ is very useful fluorinating agent and it is used for the production of VF₆ in the enrichment of U²³⁵.
U_(s) + 3ClF_3(l) → UF_6(g) + 3ClF_(g)

Question 3.
Why are halogens coloured?
Anšwer:
Halogens are coloured due to the absorption of radiations in visible region which results in the excitation of outer electrons to higher energy level. Halogens absorb different quanta of radiation and display different colours.

Question 4.
Write the reactions of F₂ and Cl₂ with water. (TS Mar. 17) (IPE Mar. ‘14)
Answer:
Fluorine produces O₂ and O₃ on passing through water.
3F₂ + 3H₂O → 6HF + O₃
2F₂ + 2H₂O → 4HF + O₂

Question 5.
Electron gain enthalpy of fluorine is less than that of chlorine – explain.
Answer:
The negative electron gain enthalpy of the fluorine is less than that of chlorine. This is due to small size of fluorine atom which results in strong inter electronic repulsions in the relatively small 2p orbitals of fluorine and thus the incoming electron does not experience much attraction.

Question 6.
Bond dissociation enthalpy of F₂ is less than that of Cl₂ – Explain.
Answer:
Bond dissociation enthalpy of F₂ is less than that of Cl₂
Explanation:
In F₂ molecule electron repulsions are greater among lone pairs because these lone pairs are much closer to each other than in case of Cl₂.

Question 7.
Write the formulae of the compounds, in which oxygen has positive oxidation states and mention the oxidation states of oxygen in them.
Answer:
In OF₂ and O₂F₂ oxygen has positive oxidation states.

• In OF₂, oxygen oxidation state is + 2.
• In O₂F₂ oxygen oxidation state is + 1.

Question 8.
What is the use of O₂F₂ and I₂O₅?
Answer:
Uses of O₂F₂

• O₂F₂ is a fluorinating agent. O₂F₂ oxidises plutonium to PUF₆ and the reaction is used in removing plutonium as PUF₆ from spent nuclear fuel.

Use of I₂O₅:

• I₂O₅ is a good oxidising agent and is used in the estimation of carbon monoxide (CO).

Question 9.
Explain the reactions of Cl₂ with NaOH. (IPE – 2015 (AP), 2016 (TS), (AP))
Answer:
i) Reaction with cold dilute NaOH: Chlorine reacts with cold dilute NaOH to give sodium hypochlorite and sodium chloride.

ii) Reaction with hot concentrated NaOH : Chlorine reacts with hot concentrated NaOH to give sodium chlorate and sodium chloride.

Question 10.
What happens when Cl₂ reacts with dry slaked lime ? (AP Mar. 17: IPE 16, 15 (AP))
Answer:
Chlorine reacts with dry slaked lime and forms bleaching powder.
Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O.

Question 11.
What is aqua regia ? Write its reaction with gold and platinum.
Answer:
A mixture of 3 parts of conc. HCl and one part of Conc. HNO₃ constitutes aqùa regia. It is used for dissolving noble metals.
It’s reaction with gold:
Au + 4H⁺ + \(\mathrm{NO}_3^{-}\) + 4Cl^– → \(\mathrm{AuCl}_4^{-}\) + NO + 2 H₂O
It’s reaction with Platinum:
3Pt + 16H⁺ + \(4 \mathrm{NO}_3^{-}\) + 18Cl^– → 3PtC\(l_6^{-2}\) + 4NO + 8 H₂O

Question 12.
How is chlorine manufactured by Deacon’s method? (AP Mar.’ 17: IPE ’16 (TS))
Answer:
Deacon’s process: [n Deacon’s process. Chlorine is obtained by the oxidation of hydrogen chloride gas by atmospheric oxygen in the presence of CuCl₂ (catalyst) at 723 K.

Question 13.
Why is dry chlorine cannot act as a bleaching agent.
Answer:
Dry chlorine cannot produce nascent oxygen. Hence it cannot act as a bleaching agent.

Question 14.
HF is a liquid while HCl is a gas — explain.
Answer:
HF is a liquid due to the presence of inter molecular hydrogen bonding where as HCl is a gas as there is no such type of bonding in it.

Question 15.
Write two uses of hydrogen chloride.
Answer:
Uses of hydrogen chloride:

• It is used in medicines and as a laboratory reagent.
• It is used in the manufacturing of Cl₂, NH₄Cl and glucose (from corn starch).
• It is used in extracting glue from bones and purifying bone black.

Question 16.
Chlorine acts as an oxidizing agent – explain with two examples.
Answer:
Chlorine acts as oxidising agent.
Example – 1: Cl₂ oxidises Iodine to Iodate.
I₂ + 6 H₂O + 5 Cl₂ → 2HIO₃ + 10 HCl

Example – 2: Cl₂ oxidises Sodium Sulphite to Sodium Sulphate.
Cl₂ + Na₂SO₃ + H₂O → Na₂SO₄ + 2 HCl

Question 17.
Write the reaction of chlorine with hypo (Na₂S₂O₃). (IPE Mar.2015 (AP, TS), 2016 (TS), (AP))
Answer:
Reaction of chlorine with hypo (Na₂S₂O₃). Na₂S₂O₃ + Cl₂ + H₂O → Na₂SO₄ + 2HCl + S. In this reaction hypo acts an “antichlor”.

Question 18.
Give the bond dissociation order of halogens.
Answer:
Bond dissociation order of halogens is, Cl₂ > Br₂ > F₂ > I₂.

Question 19.
I₂ is more soluble in KI give reason.
Answer:
I₂ forms soluble KI₃ with KI solution. I₂ + KI → KI₃.

Question 20.
Chlorine acts as a bleaching agent only in the presence of moisture — explain.
Answer:
Moist chlorine is a powerful bleaching agent. This bleaching property is due to oxidation.
Cl₂ + H₂O → 2HCl + (O)
Ex: Coloured substance + (0) → colourless substance.

Question 21.
The decreasing order of acidic character among hypohalogen acids is HClO > HBrO > HIO. Give reason.
Answer:
Given the decreasing order of acidic character among hypohalogen acids is
HClO > HBrO > HIO

From the above mentioned Ka values the given order of hypohalogen acids – acid strength order is
HClO > HBrO > HIO

Question 22.
fluorine exhibits only-1 oxidation state whereas other halogens exhibit +1, +3, +5 and +7 oxidation states also. Explain.
Solution:
Fluorine is the most electronegative element and cannot exhibit any positive oxidation state. Other halogens have d- orbitais and therefore, can expand their octets and show +1, +3, +5 and +7 oxidation states also.

Question 23.
What are the inter halogen compounds ? Give two examples.
Answer:
The compounds formed between different halogens are called inter halogen compounds.
Ex: ClF₃, BrF₃, IF₇, ICl₃.

Short Answer Questions

Question 1.
Explain the structures of
a) BrF₅ and
b) IF₇.
Answer:
a) Structure of BrF₅.

• Central atom in BrF₅ is ‘Br’
• ‘Br’ undergoes sp³d² hybridisation in 2^nd excited state.
  
• Shape of the molecule is octahedral with one position occupied by a lone pair (or) square pyramidal.
  

b) Structure of IF₇:

• Central atom in IF₇ is 1’.
• ‘I’ undergoes sp³d³ hybridisation iñ 3^rd excited state.
  
• Shape of the molecule is Pentagonal bipyramid structure.
  

Question 2.
How is chlorine obtained in the laboratory? How does it react with the following?
a) cold dil. NaOH
b) excess NH₃
c) KI (IPE Mar & May – 2015 AP TS), BMP)
Answer:
In the laboratory chlorine is prepared by the oxidation of HCl with MnO₂.
4 HCl + MnO₂ → MnCl + 2 H₂O + Cl₂↑
a) Chlorine reacts with cold dil. NaOH to form sodium hypochlorite.
Cl₂ + 2 NaOH → NaCl + NaOCl + H₂O
b) Cl₂ reacts with excess of NH₃, Nitrogen and ammonium chloride are formed.
8 NH₃ + 3 Cl₂ → 6 NH₄Cl + N₂↑
c) Cl₂ reacts with KI to liberate iodine.
Cl₂ + 2KI → 2KCl + I₂↑

Question 3.
How is ClF₃ prepared? How does it react with water? Explain its structure.
Answer:
Preparation of ClF₃: Chlorine reacts with excess of fluorine to form ClF₃.

Reaction with H₂O : ClF₃ reacts with water explosively and oxidises water to give oxygen or in controlled quantitieš oxygen diflouride (OF₂) as well as HF and HCl.
ClF₃ + 2 H₂O → 3 HF + HCl + O₂
ClF₃ + H₂O → HF + HCl + OF₂

Structure of ClF₃:

• Central atom in ClF₃ is ‘Cl’
• Excited state electronic configuration of ‘Cl’ is
  
• Cl’ atom undergoes sp³d hybridisation.
• It is a bent T-shaped molecule (or) trigonal bipyramidal with 2 – positions occupied by lone pairs.
  

Question 4.
How can you prepare Cl₂ from HCl and HCl from Cl₂ ? Write the reactions.
Answer:
Preparation of Cl₂ from HCl:

• On heating MnO₂ with conc. HCl, Cl₂ gas is liberated.
  MnO₂ + 4 HCl → MnCl₂ + Cl₂ + 2 H₂O
• By the oxidation of HCl gas by atmospheric oxygen in presence of CuCl₂ catalyst at 723K.
  
  Preparation of HCl from Cl₂:
• Cl₂ when reacted with H₂ to form HCl,
  H_2(g) + Cl_2(g) → 2HCl_(g)

Question 5.
How is chlorine prepared by electrolytic method? Explain Its reaction with
a) NaOH and
b) NH₃ under different conditions. (IPE Mar & May – 2015 (AP, TS))
Answer:
Preparation of chlorine by electrolytic method: Chlorine is obtained by the electrolysis of brine solutions (Cone. NaCl). Cl₂ gas is liberated at anode.
2 NaCl → 2 Na⁺ + 2Cl^–
2 H₂O + 2e^– → 2 OH^– + H₂ (cathode)
2 Cl^– → Cl₂ + 2e^– (anode) .

a)

i)NaOH:
Chlorine reacts with cold dil. NaOH to form sodium hypochlorite.
Cl₂ + 2 NaOH → NaCl + NaOCl + H₂O
ii) Cl₂ reacts with hot conc. NaOH to form sodium chloride and sodium chlorate.
3 Cl₂ + 6 NaOH → 5 NaCl + NaClO₃ + 3 H₂O

b)

i) Cl₂ reacts with excess of NH₃, Nitrogen and ammonium chlorate are formed.
8 NH₃ + 3 Cl₂ → 6 NH₄Cl + N₂↑
ii) NH₃ reacts with excess of Cl₂ to form NCl₃ and HCl.

Question 6.
What are interhalogen compounds? Give some examples to illustrate the definition. How are they classified?
Answer:
The binary diamagnetic compounds of halogens which are formed by the reaction of halogens among themselves are called interhalogen compounds.
E.g.: IF₇, ClF₃, BrF₃, ClF, IF₃ etc.
The above examples are binary diamagnetic compounds and formed by combination of halogens only.
Inter halogen compounds are classified into four types.

1. AX – Týpe :Eg: ClF, BrF
2. AX₃ – Tÿpe : Eg : ClF₃, IF₃
3. AX₅ – Type : Eg: ClF₅, BrF₅
4. AX₇ – Type : Eg : IF₇
   • ‘A’ is less electronegative halogen.
   • X is more electronegative halogens.

Question 7.
Write the names and formulae of the oxoacids of chlorine. Explain their structures and relative acidic nature.
Answer:
Four oxyacids of chlorine are known. They are
Hypochlorous acid – HOCl
Chlorous acid — HClO₂
Chloric acid – HClO₃
Perchloric acid – HClO₄
Structure of HClO: In this chlorine atom is sp³ hybridised. Outer electronic configuration of Cl in ClO^– after sp³ hybridisation.

Shape is tetrahedral with 3 lone pairs (or) linear
No π — bonds.
Chlorous acid: (HClO₂) : Chlorine is in sp³ hybrid state, in first excited state. Shape is tetrahedral with 2 lone pairs (or) angular one π_d-p bond is present.
First excited state

Chloric acid (HClO₃) : The central chlorine atom undergoes sp³ hybridisation in second excited state.
Second excited state

Shape is tetrahedral with one lone pair (or) pyramidal.
Two π_d-p bonds present.

Perchloric acid (HClO₄) : The central chlorine atom undergoes sp³ hybridisation in third excited state.

Shape is perfect tetrahedral. No lone pairs.
Three π_d-p bonds present.