94420 + Interview Questions in Chemistry in Class 12

1.	Fluorine oxidizes HSO_4^(-) to â€¦â€¦
Answer» `S_2O_3^(2-)` `S_2O_8^(2-)` `S_4O_6^(2-)` `SO_2` Solution :`F_2` OXIDISES warm solution of POTASSIUM hydrogen SULPHATE to peroxydisulfate. `2HSO_4^(-) +F_2 to S_2O_8^(2-) + 2HF` `F_2`also oxidises chlorates to perchlorates and `CR^(3+)` SALTS to dichromates

Discussion

2.	The conjugate base of HSO_(4)^(-) ion is ……..
Answer» `S_(2) O_(3)^(2-)` `S_(2) O_(8)^(2-)` `S_(4) O_(6)^(2-)` `SO_(2)` ANSWER :B

Discussion

3.	Fluorine is usually obtained from:
Answer» Fluorspar Fluorapatite Cryolite Tetrafluoromethane Answer :A

Discussion

4.	Fluorine is the most reactive of all four common halogens.
Answer» Solution :`F_(2)` is most reactive of all the FOUR common halogens (`F_(2), Cl_(2), Br_(2) and I_(2)`) because of the following reasons : (i) `F_(2)` has the LOWEST bond dissociation enthalpy. (ii) The bonds formed between F and most of the elements are much stronger than those formed by other halogens. (iii) `F_(2)` has the highest electrode potential (+ 2.8+N397 V) of the four halogens, therefore, `F_(2)` is the STRONGEST oxidising AGENT and hence can be reduced more readily as compared to `Cl_(2), Br_(2) and I_(2)`.

Discussion

5.	Fluorine is stronger oxidizing agent than chlorine in aqueous solution. This can be stributed to the property
Answer» HEAT of DISSOCIATION electron affinity ionization potention heat of HYDRATION Answer :A::B::D

Discussion

6.	Fluorine is stronger oxidising agent. This is attributed to many factors except
Answer» HEAT of DISSOCIATION REDUCTION potential Ionisation potential Heat of hydration. Answer :C

Discussion

7.	Fluorine is prepared by
Answer» OXIDATION of `HF` Electrolysis of `KF` Electrolysis of fused `KHF_(2)` Deomposition of `HgF_(2)` SOLUTION :`KHF_(2)rarrKF+HF` `KFrarrK^(+)+F^(-)` At cathode: `K^(+)+e^(-)rarrK` `2K+2HFrarr2KF+H_(2)` At anode:`F^(-)rarrF+e^(-)` `F+FrarrF_(2)`

Discussion

8.	Fluorine is present in a small quantities in
Answer» Kidney Heart Bones and TEETH LIVER SOLUTION :TRACES of Fluorine OCCURS in bones and teeth.

Discussion

9.	Fluorine is obtained by the interaction of K_2MnF_6 with Lewis acid SbF_5 because of the :
Answer» ACIDOLYSIS of `MnF_4` DECOMPOSITION of `MnF_4` IONIZATION of `MnF_4` Decomposition of `SbF_6` ANSWER :B

Discussion

10.	Fluorine is more electronegative than chlorine even then p-fluorobenzoic acid is a weaker aci than p-chlorobenzoic acid. Explan.
Answer» Solution :Since halogens are more ELECTRONEGATIVE than carbon and also POSSESS lone pairs of ELECTRONS, therefore, they exert both -I- and +R- EFFECTS. Now in F, the lone pairs of electrons are present in 2p-orbitals but in Cl, they are present in 3p-orbitals. since 2p-orbitals of F and C are of almost equal size, therefore, the effect is more pronoiunced in p-fluorobenzoic acid than in p-chlorobenzoic acid. Thus, in p-fluorobenzoic acid, +R-effect outweighs the -I-effect but is p-chlorobenzoic acid, it is the -I- effect which outweighs the +R-effect. consequently, p-fluorobenzoic acid is a WEAKER acid than p-chlorobenzoic acid.

Discussion

11.	Fluorine is a very strong oxidising agent:
Answer» It has several isotopes It is very small and has SEVEN electrons in its VALENCY shell It is the first MEMBER of the halogen series Its valency is one. Answer :B

Discussion

12.	Fluorine is highly reactive due to
Answer» its high electronegativity smallest size of its ATOMS LOW bond dissociation energy non-availability of d-orbitals Solution :F ELECTRONIC configuration is `1s^2 2s^2 2p^5` does not have d-orbital. (as second principal SHELL does not CONTAIN d-orbital)

Discussion

13.	Fluorine is highly reactive because of:
Answer» Highest electronegativity Low BOND dissociation energy BOTH (A) AND(B) None Answer :C

Discussion

14.	Fluorine is a stronger oxidising agent than chlorine in aqueous solution. This is attributed to many factors except:
Answer» HEAT of dissociation Electron affinity Ionisation potential Heat of hydration Answer :C

Discussion

15.	Fluorine is a stronger oxidising agent than chlorine in aqueous solution . This is attributed to many factors except
Answer» Heat of dissociation Electron affinity Ionization POTENTIAL Heat of hydration ANSWER :C

Discussion

16.	Fluorine is a strong oxidising agent because :
Answer» It has several isotopes It is very SMALL and has 7 ELECTRONS in valency shell Its valency is one It is the FIRST member of the halogen series Answer :B

Discussion

17.	Fluorine is a powerful oxidising agent. Why?
Answer» SOLUTION :Fluorine has the smallest SIZE and highest electronegativity among halogens, HENCE it is a powerful oxidising AGENT.

Discussion

18.	Fluorine is a constituent of each of the following except :
Answer» Teflon Fluorocarbons Chloroform Freon. Answer :C

Discussion

19.	Fluorine gas is stored in:
Answer» COPPER vessels Steel vessels BOTH (A) AND(B) None Answer :C

Discussion

20.	Fluorine forms chemical compounds with
Answer» He NE AR XE ANSWER :D

Discussion

21.	Fluorine exhibits only-1 oxidation state whereas other halogens exhibit +1, +3, +5 and +7 oxidation states also. Explain.
Answer» Solution :Fluorine is the most electronegative element and cannot exhibit any positive oxidation STATE. Other halogens have d-orbitals and THEREFORE, can expand their octets and show (+1), (+3), (+5) and (+7) oxidation STATES also.

Discussion

22.	Fluorine exhibits only-1 oxidation state, while iodine exhibits oxidation states of -1,+1,+3,+5 and+7. This is due to :
Answer» FLUORINE being a gas Available d-orbitals in IODINE Non-availability of d-orbitals in iodine NONE of the above Answer :B

Discussion

23.	Fluorine exhibits only -1 oxidation state whereas other halogens exhibit +1, +3, +5 and +7 oxidation states. Explain.
Answer» Solution :Fluorine, like other halogens, has seven electrons in the valence shell and thus accepts one more ELECTRON to acquire the stable electronic configuration of the nearest noble gas. Therefore, like other halogens, it also exhibits and oxidation state of -1. Further, since fluorine is the most electronegative element known, it cannot share its unpaired electron with an element more electronegative than itself and hence cannot show an oxidation state of +1 (except in HOF). However, other halogens (Cl, Br, I) can share their respective unpaired electron with more electronegative ELEMENTS such as F and O and hence can show positive oxidation state of +1. Further, fluorine does not have d-orbitals in its valence shell. Therefore, it cannot expand its valence shell and hence does not show higher positive oxidation states of +3, +5 and +7. On the other hand, other halogens have VACANT d-orbitals and, therefore, can expand their octets by EXCITING one, two or even three electrons form ns and np orbitals to nd-orbitals. As a result, 3, 5 and 7 half-filled orbitals are made available for bond formation and hence, Cl, Br and I also show higher positive oxidation states of +3, +5 and +7. Thus, form the above discussion, it follows that fluorine SHOWS only -1 oxidation state while other halogens show positive oxidation states of +1, +3, +5 and +7.

Discussion

24.	Fluorine exhibits only - 1 oxidation state , whereas other halogens exhibit +1,+3,+5and +7 oxidation states . Explain.
Answer» SOLUTION :FLUORINE has no d - orbital for EXCITATION of electrons and it is most electronegative element. Hence it shows OXIDATION STATE of -1 only.

Discussion

25.	Fluorine does not show variable oxidation state due to :
Answer» SMALL size of its atoms low BOND DISSOCIATION energy non - AVAILABILITY of d - orbitals its HIGH electronegativity. Answer :D

Discussion

26.	Fluorine does not show positive oxidation states because:
Answer» It is most electronegative element It forms only ANIONS in IONIC compounds It cannot FORM multiple bonds It shows non-bonded ELECTRON pair repulsion DUE to small size Answer :A

Discussion

27.	Fluorine does not exhibit any positive oxidation states. Explain.
Answer» Solution :The electron configuration of F is `1s^(2)2s^(2)2p_(x)^(2)2p_(y)^(2)2p_(z)^(1)`. It has ONE unpaired electron. Since F is the most electronegative element KNOWN, THEREFORE, the possibility of sharing its unpaired electron with an element more electronegative than itself does not arise and hence it cannot show an OXIDATION state of +I. Further, F does not have d-orbitals in its valence shell. Therefore, it cannot expand its valence shell and hence does not show higher positive oxidation states of +3, +5 and +7. Thus, in nutshell, F cannot show any positive oxidation states.

Discussion

28.	Fluorine does not show positive oxidation states becaouse
Answer» It is most electronegative element If forms only anions in IONIC compounds It cannot form MULTIPLE bonds It shows non-bonded electron pair repulsion DUE to SMALL size. Solution :`F_(2)`BOND dissociation energy is low because of repulsion between non-bonding electrons

Discussion

29.	Explain the following observations : (i) Fluorine does not exhibit any positive oxidation state. (ii) The majority of known noble gas compounds are those of Xenon. (iii) Phosphorus is much more reactive than nitrogen.
Answer» Solution :FLUORINE being the most ELECTRONEGATIVE element, does not exhibit any oxidation STATE.

Discussion

30.	Fluorine does not show positive oxidation due to the absence of:
Answer» p-orbitals d-orbitals s-orbitals None Answer :B

Discussion

31.	Fluorine does not exhibit any positive oxidation state. Why?
Answer» Solution :Fluorine is a strongly electronegative ELEMENT. It has no TENDENCY to give electrons. Therefore, it does not EXHIBIT any POSITIVE OXIDATION state.

Discussion

32.	Fluorine can not be obtained from fluoride by chemical methods. Why ?
Answer» Solution :OXIDATION of fluoride is shown as `2F^(-) RARR 2e^(-) + F_(2)` The above oxidation can not be performed using a chemical substance, because FLUORINE itself is the best OXIDANT.

Discussion

33.	Fluorine, chlroine, bromine and iodine are placed in the same group (17) of the periodic table, because
Answer» They are non-metals They are ELECTRONEGATIVE Their atoms are generally univalent They have 7 ELECTRONS in the outermost shell of their atom Solution :Electronic CONFIGURATION of outermost shell of group-17 or HALOGENS are `ns^(2)np^(5)` .

Discussion

34.	Fluorine cannot be prepared by chemical oxidation of F^(-) ion-explain.
Answer» Solution :Fluorine is the smallest halogen with the HIGHEST electronegativity and so `F^(-)` is very stable. Hence, it is impossible for any oxidising AGENT to REMOVE an ELECTRON from `F^(-)` ion and liberate F-atom (or `F_(2)` MOLECULE). Therefore, `F_(2)` cannot be prepared by chemical oxidation of `F^(-)` ion.

Discussion

35.	Fluorine can be prepared by each of the following methods except
Answer» Whytlaw-Gray's METHOD Dennis method Moissan method PARKE's method Solution :Parke's method is USED for DESILVERISATION of LEAD

Discussion

36.	Fluorine can be prepared by heating NaF and MnO_2 with conc. sulfuric acid.
Answer» SOLUTION : Fluorine cannot be PREPARED by heating NAF and `MnO_2`, with conc. SULFURIC acid.

Discussion

37.	Fluorine as compared to air is
Answer» lighter heavier the same VAPOUR density none of these Answer :B

Discussion

38.	Fluorine can be freed from HF by passing the mixture through:
Answer» `H_2O` An ALKALINE solution Conc.`H_2SO_4` NaF Answer :A

Discussion

39.	Fluorine - 18 is a radioactive isotope that decays by positron emission to form oxygen - 18 with a half-life of 100 min. Physicians use ^(18)F for the study of brain by injecting a quantity of fluoro substituted glucose into the blood of a patient The glucose accummulates in the region where the brain is active and needs nourishment. If a sample of glucose that contains .^(18)F is injected into the blood what percentange will remain after 5 hours?
Answer» `12.5` 50 25 `6.25` ANSWER :A

Discussion

40.	Fluorine - 18 is a radioactive isotope that decays by positron emission to form oxygen - 18 with a half-life of 100 min. Physicians use ^(18)F for the study of brain by injecting a quantity of fluoro substituted glucose into the blood of a patient The glucose accummulates in the region where the brain is active and needs nourishment. How long does it take for 99.9% decay of .^(18)F ?
Answer» INFINITE TIME `16.67` hourse 10 HRS `33.33` hours Answer :B

Discussion

41.	Fluorine absorbs….portion of light and appears yellow:
Answer» Yellow Green Violet Red Answer :C

Discussion

42.	Fluorine - 18 is a radioactive isotope that decays by positron emission to form oxygen - 18 with a half-life of 100 min. Physicians use ^(18)F for the study of brain by injecting a quantity of fluoro substituted glucose into the blood of a patient The glucose accummulates in the region where the brain is active and needs nourishment. What is the average life for decomposition of 18_(F)?
Answer» 100 MIN 200 min `69.3` min 144 min Answer :D

Discussion

43.	Fluoride ion has higher hydration enthalpy than chloride ion. Give reasons.
Answer» Solution :Due to smaller size of F over CI, the electron DENSITY on the F atom is HIGHER than on CI atom. Therefore, F attracts H of `H_(2)O` molecule more strongly than CI does and hence hydratio energy of F is higher than that of CI.

Discussion

44.	Fluoride ion differs from fluorine atom in the number of:
Answer» Protons Electrons Neutrons Protons and neutrons Answer :B

Discussion

45.	Fluorides and iodides of hydrocarbons are best prepared by ______________ method.
Answer» ANSWER :HALOGEN EXCHANGE

Discussion

46.	Fluorescin, a well known dye is obtained by the reactions of
Answer» Phthalic ANHYDRIDE and phenol Phthalic anhydride and RESORCINOL Succinic acid and resorcinol Phthalic anhydride and catechol Solution :Fluorescin is OBTAINED by the reaction of Phthalic anhydride and resorcinol.

Discussion

47.	Flourine reacts with uranium to produce uranium hexaflouride , UF_(6), as represented by this equation U(s) + 3F_(2)(g) to UF_(6)(g) How many fluorine molecules are required to produce 7.04 mg of uranium hexafluoride , UF_(6) , from an excess of uranium? The molar mass of UF_(6) is 352 gm/mol (N_(A)=6xx10^(23))
Answer» ANSWER :`3.6xx10^(19)`

Discussion

48.	Fluorapatite is a mineral of:
Answer» `F_2` `Br_2` P As Answer :C

Discussion

49.	Flouro benzene cannot be prepared by direct flourination since
Answer» `F_2` is HIGHLY REACTIVE ` F_2` is INERT Reaction with `F_2` REVERSIBLE `F_2` REACTS slowly Answer :A

Discussion

50.	Flourine is prepared by electrolysis. What is the liquid used and electrodes ?
Answer» SOLUTION :ELECTROLYTE is FUSED `KHF_2` and ELECTRODES are GRAPHITE.

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

Fluorine oxidizes HSO_4^(-) to â€¦â€¦

The conjugate base of HSO_(4)^(-) ion is ……..

Fluorine is usually obtained from:

Fluorine is the most reactive of all four common halogens.

Fluorine is stronger oxidizing agent than chlorine in aqueous solution. This can be stributed to the property

Fluorine is stronger oxidising agent. This is attributed to many factors except

Fluorine is prepared by

Fluorine is present in a small quantities in

Fluorine is obtained by the interaction of K_2MnF_6 with Lewis acid SbF_5 because of the :

Fluorine is more electronegative than chlorine even then p-fluorobenzoic acid is a weaker aci than p-chlorobenzoic acid. Explan.

Fluorine is a very strong oxidising agent:

Fluorine is highly reactive due to

Fluorine is highly reactive because of:

Fluorine is a stronger oxidising agent than chlorine in aqueous solution. This is attributed to many factors except:

Fluorine is a stronger oxidising agent than chlorine in aqueous solution . This is attributed to many factors except

Fluorine is a strong oxidising agent because :

Fluorine is a powerful oxidising agent. Why?

Fluorine is a constituent of each of the following except :

Fluorine gas is stored in:

Fluorine forms chemical compounds with

Fluorine exhibits only-1 oxidation state whereas other halogens exhibit +1, +3, +5 and +7 oxidation states also. Explain.

Fluorine exhibits only-1 oxidation state, while iodine exhibits oxidation states of -1,+1,+3,+5 and+7. This is due to :

Fluorine exhibits only -1 oxidation state whereas other halogens exhibit +1, +3, +5 and +7 oxidation states. Explain.

Fluorine exhibits only - 1 oxidation state , whereas other halogens exhibit +1,+3,+5and +7 oxidation states . Explain.

Fluorine does not show variable oxidation state due to :

Fluorine does not show positive oxidation states because:

Fluorine does not exhibit any positive oxidation states. Explain.

Fluorine does not show positive oxidation states becaouse

Explain the following observations : (i) Fluorine does not exhibit any positive oxidation state. (ii) The majority of known noble gas compounds are those of Xenon. (iii) Phosphorus is much more reactive than nitrogen.

Fluorine does not show positive oxidation due to the absence of:

Fluorine does not exhibit any positive oxidation state. Why?

Fluorine can not be obtained from fluoride by chemical methods. Why ?

Fluorine, chlroine, bromine and iodine are placed in the same group (17) of the periodic table, because

Fluorine cannot be prepared by chemical oxidation of F^(-) ion-explain.

Fluorine can be prepared by each of the following methods except

Fluorine can be prepared by heating NaF and MnO_2 with conc. sulfuric acid.

Fluorine as compared to air is

Fluorine can be freed from HF by passing the mixture through:

Fluorine absorbs….portion of light and appears yellow:

Fluoride ion has higher hydration enthalpy than chloride ion. Give reasons.

Fluoride ion differs from fluorine atom in the number of:

Fluorides and iodides of hydrocarbons are best prepared by ______________ method.

Fluorescin, a well known dye is obtained by the reactions of

Fluorapatite is a mineral of:

Flouro benzene cannot be prepared by direct flourination since

Flourine is prepared by electrolysis. What is the liquid used and electrodes ?