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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
`0.80 g` of sample of impure potassium dichromate was dissolved in water and made up to `500 mL` solution. `25 mL` of this solution treated with excess of `KI` in acidic medium and `I_(2)` liberated required `24 mL` of a sodium thiosulphate solution. `30 mL` of this sodium thiosulphate solution required `15 mL` of `N//20` solution of pure potassium dichromate. What was the percentage of `K_(2)Cr_(2)O_(7)` in given sample?A. `73.5%`B. `75.3%`C. `36.75%`D. none of these |
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Answer» Correct Answer - A `K_(2)Cr_(2)O_(7)+KI rarr I_(2)+Cr^(3+)` `I_(2)+Na_(2)S_(2)O_(3) rarr I_(2)+S_(4)O_(6)^(2-)` `Na_(2)S_(2)O_(3)+K_(2)Cr_(2)O_(7) rarr` Meq. Of `Na_(2)S_(2)O_(3) rar` Meq. Of `K_(2)Cr_(2)O_(7)` `30xxN=15xx(1)/(20)N=(1)/(40)` Meq. of `I_(2)=` Meq. of `Hypo` Meq. of `I_(2)=` Meq. of `KI` Meq. of `KI=` Meq. of `K_(2)Cr_(2)O_(7)` `24xx(1)/(40)=` Meq. of `25mL K_(2)Cr_(2)O_(7)` Meq. of `500 mL K_(2)Cr_(2)O_(7)=(24)/(40)xx(500)/(25)` `(wxx6)/(294)xx1000=12`, `w=0.588` `% purity=(0.588)/(0.8)xx100=73.5%` |
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| 2. |
`12. g` of an impure sample of arsenious oxide was dissolved in water containing `7.5 g` of sodium bicarbonate and the resulting solution was diluted to `250 mL`. `25 mL` of this solution was completely oxidised by `22.4 mL` of a solution of iodine. `25 mL` of this iodine solution reacted with same volume of a solution containing `24.8 g` of sodium thiosulphate `(Na_(2)S_(2)O_(3).5H_(2)O)` in one litre. Calculate teh percentage of arsenious oxide in the sample ( Atomic mass of `As=57`) |
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Answer» `As_(2)O_(3)` sample`=12.0 g` , it reacts with `NaHCO_(3)` to give `Na_(3)AsO_(3)`. Its reaction with `I_(2)` shows the changes: `{:(As_(2)^(3+),rarr,As_(2)^(5+)+,4e, ,),(I_(2)+2e,rarr,2I^(-),,):}` Meq.of `As_(2)O_(3)` in `25 mL=` Meq.of `I_(2)` `=22.4xxN`....(1) Also `N` of `I_(2)` can be evaluated as: The reaction are: `I_(2)+2erarr2I^(-)` `2S_(2)O_(3)^(2-)rarrS_(4)O_(6)^(2-)+2e` Meq.of `I_(2)=` Meq.of hypo `=NxxV` `Nxx25=(24.8)/(248xx1)xx25` `therefore N_(12)=(N)/(10)` `therefore "Meq.of" As_(2)O_(3)"in" 25 mL=22.4xx(1)/(10)=2.24` or `"Meq.of" As_(2)O_(3)"in" 250 mL=2.24xx(250)/(25)=22.4` or `(w)/(E.wt.)xx1000=22.4` `(w)/((198)/(4))xx1000=22.4` `therefore w_(As_(2)O_(3))=(22.4xx198)/(4xx1000)=1.1088` `therefore % "of" As_(2)O_(3)=(1.1088)/(12)xx100=9.24%` |
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| 3. |
The unbalanced equation for the reaction of `P_(4)S_(3)` with nitrate in aqueous acidic medium is given below : `P_(4)S_(3)+NO_(3)^(-)rarrH_(3)PO_(4)+SO_(4)^(2-)+NO` the number of moles of water reuired per mole of `P_(4)S_(3)` is :A. 18B. `(8)/(3)`C. 8D. 28 |
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Answer» Correct Answer - b |
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| 4. |
Complete and balance the following in acidic medium: `Ag^(o+)+AsH_(3)rarrH_(3)AsO_(3)` |
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Answer» `Aoverset(+1)(g^(o+))+Aoverset(-3)sH_(3)rarrH_(3)Aoverset(+3)sO_(3)` a. `As^(3-)rarrAs^(3+)`(oxidation) b. `Ag^(o+)rarrAg^(x) x=?` Clearly. (b) must be a reduction, so `x` must be `0`, as `x` cannot be negative for `Ag` (silver being metal). a. `As^(3-)rarrAs^(3+)+6e^(-)` b. `Ag^(o+)+1e^(-)Ag^(0)` `As^(3-)+6Ag^(o+)rarrAs^(3-)+6Ag^(0)` `AsH_(3)+6Ag^(o+)rarr6Ag^(0)+H_(3)AsO_(3)` Now balance charge by adding `6H^(o+)` on right side and finally add `3H_(2)O` on left side. `AsH_(3)+6Ag^(o+)+3H_(2)OrarrAg+H_(3)AsO_(3)+6H^(o+)` |
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| 5. |
Balance the following equation stepwise: `Cr_(2)O_(7)^(2-) + Fe^(2+)++H^(o+)rarrCr^(3+) + Fe^(3+) + H_(2)O`A. `6`, `7`B. `6`, `14`C. `5`, `7`D. `5`, `14` |
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Answer» Correct Answer - B `Cr_(2)O_(7)^(2-)+6Fe^(2+)+14H^(+) rarr Cr^(3+)+6Fe^(3+)+7H_(2)O`. |
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| 6. |
Balance the following equations: (i) `Cr_(2)O_(7)^(2-)+I^(-)+H^(+)rarrCr^(3+)+I_(2)+H_(2)O` (ii) `Ag^(+)+AsH_(3)rarrH_(3)AsO_(3)+H^(+)+....` |
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Answer» (i) `Cr_(2)O_(7)^(2-)+6I^(-)+14H^(+)rarr2Cr^(3+)+3I_(2)+7H_(2)O` (ii) `6Ag^(+)+AsH_(3)+3H_(2)Orarr6Ag+6H^(+)+H_(3)AsO_(3)` |
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| 7. |
`Cr_(2)O_(7)^(-2)+I^(-)+H^(+)rarrCr^(+3)+I_(2)+H_(2)O` The equivalent weight of the reductant in the above equation is :- (At. wt. of Cr = 52, I = 127)A. 26B. 127C. 63.5D. 10.4 |
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Answer» Correct Answer - B `I^(Theta)rarrI_(2)` `v.f.=1` `"Eq.wt"=(127)/(1)` |
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| 8. |
`Cr_(2)O_(7)^(2-)+Xoverset(H^(o+))rarrCr^(3+)+H_(2)O+ "oxidised product" of X, X` in the above reaction cannot beA. `C_(2)O_(4)^(2-)`B. `Fe^(2+)`C. `SO_(4)^(2-)`D. `SO_(2-)` |
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Answer» Correct Answer - C `SO_(4)^(2-)` cannot be oxidised since the oxidation state `(+6)` of `S` is highest. |
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| 9. |
Which of the following is a set fo reducing agents ?A. ` Cr_2O_7^(2-), CrO_4^(2-), Na`B. `I^(-) , Na, Fe^(2+)`C. `F^(-) , Cl^(-) , MnO_4^(-)`D. `HNO_3, Fe^(2+), F_(2)` |
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Answer» Correct Answer - B A species can act as a reducing agent if the central atom is not present in its highest oxidation state. In option (4), N in `HNO_3` has the highest oxidation state , ` +5` . In option (3), `Mn` in ` MnO_4^(-)` has the highest oxidation state, ` +7`, and in option (4), `Cr` in ` Cr_2O_7^(2-)` has the highest oxidation state, ` +6` Thus, all the species in option (2) will act as reducing agents. |
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| 10. |
`Cr_(2)O_(7)^(2-)overset(H^(+))rarrCr^(3+)`, Eq. wt. of `Cr_(2)O_(7)^(2-)` is :-A. mol. Wt/6B. mol. Wt/3C. mol. Wt/4D. mol. Wt/1 |
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Answer» Correct Answer - A Reduction of `Cr_(2)O_(7)^(2-)` to `Cr^(3+)` is `6e^(-)` change `Cr_(2)O_(7)^(2-)+14H^(+)+6e^(-)rarr2Cr^(3+)+7H_(2)O` `:.` Eq. wt of `Cr_(2)O_(7)^(2-) =` Mol. Wt/6. |
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| 11. |
Which of the following is a set of reducing agents ?A. `HNO_(3),Fe^(2+),F_(2)`B. `F,Cl^(-),MnO_(4)^(-)`C. `I^(-),Na,Fe^(2+)`D. `CrO_(7)^(2-),CrO_(4)^(2-),Na` |
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Answer» Correct Answer - C `2I^(-)rarrI_(2)+2e^(-)` `NararrNa^(+)+e^(-)` `Fe^(2+)rarrFe^(3+)+e^(-)` As `I^(-)`, Na and `Fe^(2+)` can easily lose one or more electrons, they are all good reducing agents. |
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| 12. |
Assertion: Nitrous acid (`HNO_(2)`) may act as an oxidising as well as a reducing agent. Reason: The oxidation number of nitrogen remains same in all the compounds.A. If both assertion and reason are true and the reason is the correct explanation of the assertion.B. If both assertion and reason are true but reason is not the correct explantion of the assertion.C. If assertion is true but reason is false.D. If assertion is false but reason is true. |
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Answer» Correct Answer - C Oxidation no. of `N` is `+3` in `HNO_(3)` lying between `-3` and `+5`. |
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| 13. |
Which one of the following is not a redox reaction :-A. `CaCO_(3)rarrCaO+CO_(2)`B. `2H_(2)+O_(2)rarr2H_(2)O`C. `Na+H_(2)Orarr NaOH+(1)/(2)H_(2)`D. `MnCl_(3)rarr MnCl_(2)+(1)/(2)Cl_(2)` |
| Answer» Correct Answer - A | |
| 14. |
Select the example of desproportionaton reactionA. `BaCl_(2)+H_(2)SO_(4)rarrBaSO_(4)+2HCl`B. `NH_(4)NO_(3)rarrN_(2)O+2H_(2)O`C. `4H_(3)PO_(3)rarrPH_(3)+3H_(3)PO_(4)`D. `AgCl+2NH_(3)rarrAg(NH_(3))_(2)Cl` |
| Answer» Correct Answer - C | |
| 15. |
`KMnO_(4)` is a strong oxidising agent in acidic medium. To provide acidic medium `H_(2)SO_(4)` is used instead of HCl. This is becauseA. `H_(2)SO_(4)` is a stronger acid than HClB. HCl is oxidised by `KMnO_(4)` to `Cl_(2)`C. `H_(2)SO_(4)` is a dibasic acidD. Rate is faster in the presence of `H_(2)SO_(4)` |
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Answer» Correct Answer - B HCl is oxidized by `KMnO_(4)` to `Cl_(2)` `2KMnO_(4)+16HClrarr2KCl+2MnCl_(2)+8H_(2)O+5Cl_(2)`. |
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| 16. |
Which of the following can act as an oxidising agent as well as a reducing agent? 1. `H_(2)O_(2)`, 2. `H_(2)S`, 3. `SO_(2)`, 4. `HNO_(2)`A. `1,2,3`B. `2,3,4`C. `1,3,4`D. All |
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Answer» Correct Answer - C 1. `H_(2)O_(2)` undergoes oxidaton to `O_(2)` and also undergoes reduction to give `H_(2)O` (`-1` oxidation state to `0` and `-2`). 2. `S^(2-)` undergoes only oxidation either to `S,SO_(2)` or `SO_(4)^(2-)` in which oxidation number changes from `-2` to `0,+4`, or +6` `3. `SO_(2)` (oxidation number of `S` is `+4`) can undergo oxidation and reductio. `S` is having highest oxidation state of `+6`. The element in a molecule having its oxidation state in the middle (i.e. minimum and lt maximum) can be used os oxidant and as reductant both. 4. `HNO_(2)` (oxidation number of `N` is `+3`). Highest oxidation state of `N` is `+5`. So it can undergo both oxidant and reductant. |
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| 17. |
Which of the following reaction represents the oxidising behaviour of `H_(2)SO_(4)` :-A. `2PCl_(5)+H_(2)SO_(4)rarr2POCl_(3)+2HCl+SO_(2)Cl_(2)`B. `2NaOH+H_(2)SO_(4)rarrNa_(2)SO_(4)+2H_(2)O`C. `NaCl+H_(2)SO_(4)rarrNaHSO_(4)+HCl`D. `2HI+H_(2)SO_(4)rarrI_(2)+SO_(2)+2H_(2)O` |
| Answer» Correct Answer - D | |
| 18. |
The oxidation number of iron in the compound `K_(4)[Fe(CN)_(6)]` isA. `+`2B. `+4`C. `+3`D. `+6` |
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Answer» Correct Answer - A `K_(4)[overset(*)(F)e(CN)_(6)]` `1xx4+x+(-1xx6)=0`, `4+x-6=0`. `x=+2`. In this complex compound iron show `+2` oxidation state. |
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| 19. |
`H_(2)SO_(4)` acts as an oxidising agent, a dehydrating agent, and an acid. Among each of the following reactions, which behaviour is shown by `H_(2)SO_(4)`? a.`C_(6)H_(12)O_(6)+H_(2)SO_(4)(conc)rarr6C+6H_(2)O` b. `5H_(2)SO_(4)(conc)+4ZnrarrH_(2)S+4Zn^(2+)+4SO_(4)^(2-)+4H_(2)O` c. `H_(2)SO_(4)(dil)+ZnrarrZn^(2+)+H_(2)+SO_(4)^(2-)` d. `H_(2)SO_(4)(dil)ZnCO_(3)rarrZn^(2+)+CO_(2)+CO_(2)+SO_(4)^(2-)+H_(2)O` |
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Answer» a. As a dehydrating agent, since it simply removes water from glucose. b. `H_(2)SO_(4)(S "in"+6 state)rarrH_(2)S(S "in" -2 state)`, i.e., acid is reduced. So it acts as an oxidising agent. c. All strong acids liberate `H_(2)` with active metals such as `Zn`(i.e, it is reduced) unless `SO_(4)^(2-)` is reduced. In this case, `H^(o+)` is reduced to `H_(2)`. So it acts as an oxidising agent. We can also call it as an acidic property. d. Simply an acid. |
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| 20. |
The oxidation number of sulphur in `H_(2)S_(2)O_(7)` and iron in `K_(4)Fe(CN)_(6)` is respectivelyA. `+6` and `+2`B. `+2` and `+2`C. `+8` and `+2`D. `+6` and `+4` |
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Answer» Correct Answer - A `H_(2)overset(*)(S_(2))O_(7)` `2xx(+1)+2xx x+7xx(-2)=0` `+2+2x-14=0` `2x=14-2=12` `x=(12)/(2)=+6` for `S` `K_(4)overset(*)(F)e(CN)_(6)` `4xx(+1)x+6xx(-1)=0` `4+x-6=0` `x=6-4=+2` for `Fe`. |
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| 21. |
Which of the following reactions has the underlined substance been reduced ?A. `ul("Carbon monoxide") +" Copper oxide " rarr " Carbon dioxide " + "Copper"`B. `ul("Copper oxide") +" Hydrochloric acid " rarr " Copper chloride " + "Water"`C. `ul("Hydrogen") +" Iron oxide " rarr " Iron " + "Water"`D. `ul("Steam") +" Iron " rarr " Iron oxide " + "Hydrogen"` |
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Answer» Correct Answer - D Steam `(H_(2)O)` is reduced to hydrogen by iron. |
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| 22. |
One mole of `N_(2)H_(4)` loses ten moles of electrons to form a new compound `A`. Assuming that all the nitrogen appears in the new compound, what is the oxidation state of nitrogen in `A`? (There is no change in the oxidation state of hydrogen.) |
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Answer» Correct Answer - 3 `N_(2)H_(4)rarr(X)+10e` `because X` contains all `N`-atoms `:. (N^(2-))_(2)rarr(2N)^(a)+10e` Therefore `2a-(-4)=10 rArr a=+3` |
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| 23. |
One mole of `N_(2)H_(4)` loses ten moles of electrons to form a new compound `A`. Assuming that all the nitrogen appears in the new compound, what is the oxidation state of nitrogen in `A`? (There is no change in the oxidation state of hydrogen.)A. `+3`B. `-3`C. `-1`D. `+5` |
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Answer» Correct Answer - A `N_(2)^(2-) rarr 2Na^(+)+10e^(-)` `:. 2a-[2xx(-2)]=10` ` :.` `a=+3`. |
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| 24. |
One mole of `N_(2)H_(4)` loses ten moles of electrons to form a new compound `A`. Assuming that all the nitrogen appears in the new compound, what is the oxidation state of nitrogen in `A`? (There is no change in the oxidation state of hydrogen.)A. `+1`B. `-3`C. `+3`D. `+5` |
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Answer» Correct Answer - C `(N^(2-))_(2)rarr2N^(a+)+10e` `:. 2a-[2xx(-2)]=10` `:. a=+_3` |
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| 25. |
What is the average oxidation number of tungesten in the ion , `W_(6)O_(6)Cl_(12)^(2-)`?A. 2.7B. 3.3C. 3.7D. 4.3 |
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Answer» Correct Answer - c |
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| 26. |
Which reaction does not represent auto redox or disproptionation?A. `Cl_(2)+OH^(-)rarrCl^(-)+ClO_(3)^(-)+H_(2)O`B. `2H_(2)O_(2)rarr2H_(2)O+O_(2)`C. `2Cu^(+)rarrCu^(2+)+Cu`D. `(NH_(4))_(2)Cr_(2)O_(7)rarrN_(2)+Cr_(2)O_(3)+4H_(2)O` |
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Answer» Correct Answer - D In auto redox or disproportionation, same elements is oxidised as well as reduced. In (a) `Cl_(2)` (b) `H_(2)O_(2)` and (c ) `Cu^(+)` is oxidised as well as reduced. In (d) `N` is oxidised and `Cr` is reduced (in one mole of `(NH_(4))_(2)Cr_(2)O_(7)`)`and thus it is intramolecular redox. |
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| 27. |
Starch iodide paper is used to test for the presence ofA. IodineB. Iodide ionC. Oxidising agnetD. Reducing agent |
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Answer» Correct Answer - C Statement is self explanatory. |
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| 28. |
The colour of `K_(2)Cr_(2)O_(7)` changes from red-orange to lemon-yellow on treatment with `KOH_((aq.))`, because of:A. reduction of Cr(VI) or Cr(III)B. formation of chromium hydroxideC. Conversion of dichromatw ion to chromateD. oxidation of potassium hydroxide to potassium peroxide |
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Answer» Correct Answer - C `K_(2)Cr_(2)O_(7)+2KOHhArr2K_(2)CrO_(4)+H_(2)O` |
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| 29. |
The colour of `K_(2)Cr_(2)O_(7)` changes from red-orange to lemon-yellow on treatment with `KOH_((aq.))`, because of:A. Reduction of `Cr(VI)` to `Cr(III)`B. Formation of chromium hydroxideC. Conversion of dichromate into chromate ionD. Oxidation of potassium hydroxide to potassium peroxide |
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Answer» Correct Answer - C `K_(2)Cr_(2)O_(7)+2KOHrarr2K_(2)CrO_(4)+H_(2)O` |
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| 30. |
Which of the following acids possesses oxidising, reducing, and complex forming properties ?A. `HNO_(3)`B. `H_(2)SO_(4)`C. `HCL`D. `HNO_(2)` |
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Answer» Correct Answer - D In `HNO_(2)`, the oxidation state of `N` is `+3`. So it can go to a higher or lower oxidation state. |
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| 31. |
`50 mL` of `0.1M` solution of a salt reacted with `25 mL` of `0.1M` solution of sodium sulphite. The half reaction for the oxidation of sulphate ion is: `SO_(3(aq.))^(2-)+H_(2)O_((l))rarrSO_(4(aq.))^(2-)+2H_(+(aq.))+2e` If the oxidation number of metal in the salt was `3`, what would be the new oxidation number of metal?A. ZeroB. `1`C. `2`D. `4` |
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Answer» Correct Answer - C Meq.of sodium sulphate`=` Meq.of salt `25xx0.1xx2=50xx0.1xxn :. n=1` (where `n` represents valence factor for metal involving no of electrons gained) Thus `M^(3+)+erarrM^(2+)` |
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| 32. |
Find the number of electrons lost by `1/6` molecule of caffine in the given combustion reaction. `C_(8)H_(10)N_(4)O_(2)+ O_(2) to CO_(2)+H_(2)O+NO_(2)` |
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Answer» Correct Answer - 9 |
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| 33. |
1.6 g of pyrolusite ore was treted with 50 " mL of " 1.0 N oxalic acid and some sulphuric acid. The oxalic acid left undecomposed was raised to 250 mL in a flask. 25 " mL of " this solution, when titrated with 0.1 N `KMnO_4` required 32 " mL of " this solution. Find out the percentage of pure `MnO_2` and also the percentage of available oxygen from `MnO_2`. |
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Answer» Meq.of `MnO_(2)=` Meq.of oxalic acid added-Meq.of oxalic acid left `=1xx50-0.1xx32xx10=18 ("in" 250 mL)` `( :. E=(86.9)/(2))` or `:. (w)/(E )xx1000=18` or `w_(MnO_(2))=(18xx86.9)/(2xx1000)=0.7821g` `:. % "of" MnO_(2)=(0.7821)/(1.6)xx100=48.88%` Also Meq.of `MnO_(2)="Meq.of" O_(2)=18` `:. (w)/(8)xx1000=18` `w_(O_(2))=0.144g` `:. %` of available `O_(2)=(0.144)/(1.6)xx100=9%` |
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| 34. |
Assertion: `Pb^(4+) "ion can easily reduced to" Pb^(2+)` ion. Reason: `Pb^(2+)` ion is paramagnetic in natureA. If both assetion and reson are corect and reason is correct explanation for assertionB. If both assetion and reason are correct but reason is not correct explanation for assertionC. If asertion is correct but reason is incorrectD. If both assetion and reason are incorrect |
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Answer» Correct Answer - C Correct reason,. `Pb^(2+)` ion is more stable than `Pb^(2+)` ion |
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| 35. |
Bleaching powder and bleach solution are produced on a large scale and used in several hous-hold products. The effectiveness of bleach solution id often measured by iodometry. `25 mL` of household bleach solution was mixed with `30 mL` of `0.50 M KI` and `10 mL` of `4N` acetic acid. In the titration of the liberated iodine, `48 mL` of `0.25 N Na_(2)S_(2)O_(3)` was used to reach the end point. The molarity of the household bleach solution is :A. 0.48MB. 0.96MC. 0.24MD. 0.024M |
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Answer» Correct Answer - c |
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| 36. |
The CO in a 20.3L sample of gas was converted to `CO_(2)` by passing the gas over iodine pentoxide heated to `150^(@)C` : `I_(2)O_(5)(s)+5CO(g)rarr5CO_(2)(g)+I_(2)(g)` The iodine distilled at this temperature and was collected in an absorber containing 8.25mL of `0.11101M Na_(2)S_(2)O_(3)` . The excess hypo was back-titrated with `2.16mL` of `0.00947M I_(2)` solution. The milligrams of `CO` in `1L` of the original gas sample was therefore:A. `0. 172mg`B. `0.283mg`C. `0.349mg`D. `0.506mg` |
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Answer» Correct Answer - a |
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| 37. |
A student working in the laboratory kept and aqueous solution of ferrous suphate in a vessel made up of zinc. After a few days, he found that the vessel had developed holes and cracks (i) why did the vessel develop holes in it ? (ii) What is the chemical reaction that takes place gt? (iii) what is the value assouciateed with this? |
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Answer» (i) Zinc is placed above iron in the reactivity series.It has therefore. Reduced `Fe^(2+)` ions to Fe and it has been oxidised (ii) `Zn(s)+Fe^(2+)(aq)rarrZn^(2+)(aq)+Fe(s)` (iii)We should be very careful while selectingh container for stroing certain chemicals. Only those metals should be used for making the vessels or container s which are not involved in any type of chemical reactions. |
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| 38. |
Can a solution of 1 M `ZnSO_(4)` be stored in a vessel made of copper ? Given that `E_(Zn^(+2)//Zn)^(@) =-0.76V and E_(Cu^(+2)//Cu)^(@)=0.34 V` |
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Answer» Reduction potential of `Cu gt Zn.` Hence , we can store `ZnSO_(4)` solution in Cu vessel |
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| 39. |
Assertion : Zinc diplaces copper from copper suphate solution Reason: The `E^(@)` of Zn is- 0.76 V and that of Cu is +0.34 V.A. If both assetion and reson are corect and reason is correct explanation for assertionB. If both assetion and reason are correct but reason is not correct explanation for assertionC. If asertion is correct but reason is incorrectD. If both assetion and reason are incorrect |
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Answer» Correct Answer - A Reason is the correct explanation for assetion |
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| 40. |
Why blue colour of `CuSO_(4)` solution gets discharged when zinc rod is dipped in it ? Given, `E_(Cu^(+2)//Cu)^(@)=0.34 V and E_(Zn^(+2)//Zn)^(@)=-0.76V` |
| Answer» Here reduction potential of `Cu gt Zn.` So, `Cu^(+2)` (aq) ions reduced to Cu(s) | |
| 41. |
What will be the volume strength of 100mL of `KMnO_4` in acidic medium? (Given that 61mL of `KMnO_4` reacts completely with 5mL of `1MK_(4) [Fe(CN)_(6))]` where it converts into `K^(+),Fe^(3+),CO_(3)^(2-) and NO_(3)^(-))`A. 17.31 VB. 34.62 VC. 18.8 VD. 19.8 V |
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Answer» Correct Answer - a |
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| 42. |
The equivalent weight of `KMnO_4` in a redox reaction in a neutral medium is .A. `M//5`B. `M`C. `M//3`D. `M//4` |
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Answer» Correct Answer - C In neutral medium, ` KMnO_4` is directly reduced to manganese dioxide : `Koverset(+7)(Mn)O_(4) rarr overset(+4)(Mn)O_(2)` Thus, the oxidation number of manganese decreases by three units . Equivalent weight ` =("Formula mass")/(("Total change in oxidation number of element"),("oxidized or reduced per mole of compound"))` ` M/3` In acidic medium : `overset(+7)(Mn)O_(4)^(-) rarr overset(+2)(M)n^(2+)` The oxidation number of Mn decrease by five units, Thus the equivalent weight of ` KMnO_4` is `M//5` Under alkaline conditions, `KMnO_4` is first reduced to potassium manganate `(K_2MnO_4)` and then to insoluble manganese oxide `(MnO_2)` : `overset(+7)(M)nO_(4)^(-) rarr overset(+4)(M)nO_(2)` Thus, the equivalent weight of ` KMnO_4` in alkaline medimum is ` M//3`. In concentrated alkalies, permanganate gives manganate : `Koverset(+7)(Mn)O_(4) rarr K_(2)overset(+6)(Mn)O_(4)` Thus, the equivalent weight of ` KMnO_4` in strongly alkaline med-ium is M. |
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| 43. |
The reaction `3ClO^(ө)(aq)rarrClO_(3)(aq)+2Cl^(ө)(aq)` is an example ofA. Oxidation reactionB. reduction reactionC. disproportionation reactionD. decomposition reaction |
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Answer» Correct Answer - C `Cl` atom is oxidized `(Cl^(+1) rarr Cl^(5+)+4e)` as well as `Cl` atom is reduced `(Cl^(1+)+2e rarr Cl^(-))`. Such reactions are called autoredox or disproportionation reactions. |
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| 44. |
The reaction `3ClO^(ө)(aq)rarrClO_(3)(aq)+2Cl^(ө)(aq)` is an example ofA. Oxidation reactionB. Reduction reactionC. DisproportionD. Decomposition |
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Answer» Correct Answer - C `Cl` atom is oxidised `(Cl^(+)rarrCl^(5+)+4e)` as well as `Cl` is reduced, `(Cl^(+)+2erarrCl^(-))` such reaction are called disproprtionation or auto-redox changes. |
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| 45. |
The oxidation number of arsenic atom in `H_(3)AsO_(4)` is :-A. `-1`B. `-3`C. `+3`D. `+5` |
| Answer» Correct Answer - D | |
| 46. |
Given that `50 0 mL` of `0.01M Na_(2)S_(2)O_(3)` solution and `5xx10^(-4)` mole of `Cl_(2)` react according to equation, `Cl_(2(g))+S_(2)O_(3)^(2-)rarrSO_(4)^(2-)+Cl^(-)+S` Answer the following: What is the molarity of `Na_(2)SO_(4)` in this solution?A. `0.080 M`B. `0.040 M`C. `0.020 M`D. `0.010 M` |
| Answer» Correct Answer - D | |
| 47. |
Given that `50 0 mL` of `0.01M Na_(2)S_(2)O_(3)` solution and `5xx10^(-4)` mole of `Cl_(2)` react according to equation, `Cl_(2(g))+S_(2)O_(3)^(2-)rarrSO_(4)^(2-)+Cl^(-)+S` Answer the following: (iii) How many equivalents of oxidising agents are in this sample for the above reaction?A. `0.001`B. `0.080`C. `0.020`D. `0.010` |
| Answer» Correct Answer - A | |
| 48. |
The reaction `3ClO^(-)(aq)rarrClO_(3)^(-)(aq)+2Cl^(-)(aq)` an example of :A. oxidationB. reductionC. disproportionationD. decomposition reaction |
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Answer» Correct Answer - c |
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| 49. |
Which one of the following connot act as an oxidizing agent ?A. `S^(2-)`B. `SO_(3)^(2-)`C. `SO_(4)^(2-)`D. `S_(2)O_(8)^(2)` |
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Answer» Correct Answer - a |
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| 50. |
What is the oxidation number of As in the compound `K(NH_(4))_(2)AsO_(4).6H_(2)O` ?A. `-3`B. `+1`C. `+3`D. `+5` |
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Answer» Correct Answer - d |
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