3195 + Interview Questions in ELECTROCHEMISTRY IN GENERAL AWARENESS Page 38 InterviewSolution

1851.	Which cell will measure standard electrode potential of copper electrode?A. `Pt(s)\|H_(2)(g,0.01" bar")\|H^(+)(aq.,1M)\|\|Cu^(2+)(aq.,1M)\|Cu`B. `Pt(s)\|H_(2)(g,1" bar")\|H^(+)(aq.,1M)\|\|Cu^(2+)(aq.,2M)\|Cu`C. `Pt(s)+H_(2)(g,1" bar")\|H^(+)(aq.,1M)\|\|Cu^(2+)(aq.,1M)\|Cu`D. `Pt(s)\|H_(2)(g,1" bar")\|H^(+)(aq.,0.1M)\|\|Cu^(2+)(aq.,1M)\|Cu`
Answer» Correct Answer - C For standard electrode potential, `[Cu^(2+)]=1M`.

Discussion

1852.	Which of the following statement is correct?A. `E_(cell) and Delta_(r),G` of cell reaction both are extensive properties.B. `E_(cell) and Delta_(r)G` of cell reaction both are intensive properties.C. `E_(cell)` is an intensive properties while `Delta_(r)G` of cell reaction is an extensive property.D. `E_(cell)` is an extensive property while `Delta_(r)G` of cell reaction is an intensive property.
Answer» Correct Answer - C `E_(cell)` is intensive while `Delta_(r)G` is extensive

Discussion

1853.	Calomel is the name ofA. HgB. `Hg_(2) Cl_(2)`C. `Hg + Hg_(2) Cl_(2)`D. `HgCl_(2)`
Answer» Correct Answer - B `Hg_(2) Cl_(2) ` is called calomel .

Discussion

1854.	The electric conduction of a salt solution in water depends on the :A. size of its moleculesB. shape of its moleculesC. size of solvent moleculesD. extent of its ionization
Answer» Correct Answer - D

Discussion

1855.	Electrode potential for Mg electrode varies according to the equation `E_(Mg^(2+)//Mg)=E_(Mg^(2+)\|Mg)^(Theta)-(0.059)/(2)"log"(1)/([Mg^(2+)])` The graph of `E_(Mg^(2+)\|Mg)` vs log `[Mg^(2+)]` isA. B. C. D.
Answer» Correct Answer - B `E=E^(@)+(0.059)/(2)log[Mg^(2+)]`. Hence, plot of E vs log`[Mg^(2+)]` will be linear with positive slope and intercept `=E^(@)` i.e., (b).

Discussion

1856.	When calomel electrode acts as an anode then the reaction isA. `2 Hg + 2 Cl^(-) to Hg_(2) Cl_(2) + 2e^(-)`B. `Hg_(2) Cl_(2) to 2 Hg^(+) + Cl_(2) + 2e^(-)`C. `Hg_(2) Cl_(2) + 2e ^(-) to 2 Hg + Cl_(2)`D. `Hg_(2) Cl_(2) + 2e^(-) to 2 Hg + 2 Cl^(-)`
Answer» Correct Answer - A The cell reactions are at anode (oxidation) `2 Hg + 2 Cl^(-) to Hg_(2) Cl_(2) + 2 e^(-)`

Discussion

1857.	The electric conduction of a salt solution in water depends on the :A. shape of moleculesB. size of its moleculesC. size of solvent moleculesD. extent of its ionisation
Answer» Correct Answer - D

Discussion

1858.	Which of the following statement is correct?(i) ECell and ΔrG of cell reaction both are extensive properties.(ii) ECell and ΔrG of cell reaction both are intensive properties.(iii) ECell is an intensive property while ΔrG of cell reaction is an extensive property.(iv) ECell is an extensive property while ΔrG of cell reaction is an intensive property.
Answer» (iii) E_Cell is an intensive property while Δ_rG of cell reaction is an extensive property.

Discussion

1859.	Which of the following reaction is possible at the angle?A. `2Cr^(2+)+7H_(2)OrarrCr_(2)O_(7)^(2-)+14H^(+)`B. `F_(2)rarr2F^(-)`C. `(1)/(2)O_(2)+3H^(+)rarrH_(2)O`D. None of these
Answer» Correct Answer - A Oxidation (loss of electrons)takes place at anode i.e., (A).

Discussion

1860.	A decinormal calomel electrode containsA. N/10 solution of `Hg_(2) Cl_(2)`B. 1 N solution of HClC. 1 N solution of `Hg_(2) Cl_(2)`D. N/10 solution of KCl
Answer» Correct Answer - D Decinormal i.e.` (N)/(10)` KCl solution .

Discussion

1861.	Which of the following statement is correct?A. `E_"cell"` and `Delta_rG` of cell reaction both are extensive properties.B. `E_"cell"` and `Delta_rG` of cell reaction both are intensive properties.C. `E_"cell"` is an intensive property while `Delta_rG` of cell reaction is an extensive property.D. `E_"cell"` is an intensive property while `Delta_rG` of cell reaction is an intensive property.
Answer» Correct Answer - C

Discussion

1862.	In electroplating, the article to be electoplated serves as:A. cathodeB. electrolyteC. anodeD. conductor
Answer» Correct Answer - A

Discussion

1863.	What mass of zinc can be produced by the electrolysis of zinc sulphate solution when a steady current of 0.015 ampere is passed for 15 minutes ? Given that atomic mass of zinc is 65.4 amu ?
Answer» Quantity of charge passed (Q) `= "Current in amperes" xx"Time in seconds"` `=(0.015 A)xx(15xx60)s=13.5 A s=13.5 C` Gram equivalent mass of zinc`=(65.4)/(2)=32.7` Now, `" " 96500" C"` of charge deposit zinc =32.7 g 13.5 C charge will deposit zinc `=((32.7 g))/((96500 C))xx(13.5 C)=4.57xx10^(-3) g`

Discussion

1864.	Assertion `(A) :` In a Daniell cell, if the concentration of `Cu^(2+)` and `Zn^(2+)` ions are doubled, the `EMF` of the cell will be doubled. Reason `(R) :` If the concentration of ions in contact with metals is doubled, the electrode potential is doubled.A. If both assertion and reason are correct and reason is correct explanation for assertion.B. If both assertion and reason are correct but reason is not correct explanation for assertion.C. If assertion is correct but reason is incorrect.D. If assertion and reason both are incorrect.
Answer» Correct Answer - C (c ) Correct reason : The effect of concentration on electrode potentialis guided by Nernst equation. On doubling the concentration, emf will remain unchanged since `([Zn^(2+)])/([Cu^(2+)])` will remain same.

Discussion

1865.	A current of 1.40 ampere is passed through 500 mL of 0.180 M solution of zinc sulphate for 200 seconds. What will be the molarity of `Zn^(2+)` ions after deposition of zinc?A. 0.154 MB. 0.177 MC. 2 MD. 0.180 M
Answer» Correct Answer - B Amount of charge passed = 1.40 x 200 = 280 Coulombs No. of moles of Zn deposited by passing 280 C charge `=1/(2xx96500)xx280`=0.00145 Molarity of zinc after deposition of zinc =`0.180-(0.00145xx1000)/500=0.80-0.0029 = 0.177` M

Discussion

1866.	These question consist of two statements each, printed as Assertion and Reason. While answering these questions you are required to choose any one of the following four responses : `Ni//Ni^(2+) (1.0 M) \|\| Au^(3+) (1.0 M) \| Au`, for this cell emf is `1. 75 V` if ` E_(Au^(3+)//Au)^@ =1.50 ` and ` E_(Ni^(3+)//Ni)^2 =0.25 V`. Emf of the cell ` =E_("cathode")^@- E_("anode")^@`.A. If both the assertion and reason are true but the reason is the correct explanation of assertionB. If both the assertion and reason are true but the reason is not the correct explanation of assertion.C. If the assertion is true but reason is false.D. If assertion is false but reason is rue
Answer» Correct Answer - A Both assertion and reason are true and reason is the correct explanation of the assertion. ` E_(Au^(3+)//Au)^@ - E_(Ni//Ni^(2+)) = 1.50 - (-0. 25) = 1. 75 V`.

Discussion

1867.	How much time is required to deposit `1xx10^(-3)` cm thick layer of silver (density is 1.05 g `cm^(-3)` ) on a surface of area 100 `cm^2` by passing a current of 5 A through `AgNO_3` solution?A. 125 sB. 115 sC. 18.7 sD. 27.25 s
Answer» Correct Answer - C Mass of Ag in coated layer = V x d `=1xx10^(-3) xx100xx1.05`=0.105 g `W=(IxxtxxEq.wt.)/96500` `t=(Wxx96500)/(IxxEq.wt.)=(0.105xx96500)/(5xx108)`=18.7 s

Discussion

1868.	These question consist of two statements each, printed as Assertion and Reason. While answering these questions you are required to choose any one of the following four responses : Assertion : For a cell reaction ` Zn(s) + Cu^(2+) (aq) rarr Zn^(2+) (aq) + Cu (s)` , at the equilibrium, voltmeter gives zero reading. Reason : At the equilibrium, there is no change in the concentration of `Cu^(2+)` and `Zn^(2+)` .A. If both assertion and reason are correct and reason is correct explanation for assertion.B. If both assertion and reason are correct but reason is not correct explanation for assertion.C. If assertion is correct but reason is incorrect.D. If assertion and reason both are incorrect.
Answer» Correct Answer - A (a) It is the correct answer.

Discussion

1869.	What will be the emf for the given cell ? `Pt\|H_(2)(g,P_(1))\|H^(+)(aq)\|H_(2)(g,P_(2))\|Pt`A. `(RT)/(F)In(p_(1))/(p_(2))`B. `(RT)/(2F)In(p_(1))/(p_(2))`C. `(RT)/(F)In(p_(1))/(p_(2))`D. None of these.
Answer» Correct Answer - B R.H.S. : `2H^(+)+2e^(-)rarrH_(2)(P_(2))` L.H.S. : `H_(2)(P_(1))rarr2H^(+)+2e^(-)` Over all reaction: `H_(2)(P_(1)) H_(2)(P_(2))` `E=E^(@)+(RT)/(nF)"In"(P_(2))/(P_(1))=0-(RT)/(2F)"In"(P_(2))/(P_(1))` `=(RT)/(2F)"in"(P_(1))/(P_(2))`.

Discussion

1870.	How much metal will be deposited when a current of 12 ampere with 75% efficiency is passed through the cell for 3 h? (Given: Z= `4xx10^(-4)` )A. 32.4 gB. 38.8 gC. 36.0 gD. 22.4 g
Answer» Correct Answer - B W= Z x I x t `=4zz10^(-4) xx 12 xx 75/100 xx 3 xx 3600` =38.8 g

Discussion

1871.	These question consist of two statements each, printed as Assertion and Reason. While answering these questions you are required to choose any one of the following four responses : For a cell raction ` Zn(s) + Cu^(2+) (aq) rarr Zn^(2+) (aq) + Cu (s)` , at the equilibrium, voltmeter gives zero reading. At the equilibrium, there is no change in teh concentration of `Cu^(2+)` and `Zn^(2+)` .A. If both the assertion and reason are true but the reason is the correct explanation of assertionB. If both the assertion and reason are true but the reason is not the correct explanation of assertion.C. If the assertion is true but reason is false.D. If assertion is false but reason is rue
Answer» Correct Answer - A ` Zn(s) + Cu^(2+) (aq) rarr Zn_(aq)^(2+) + Cu (s)` An the time passes, the concetation of ` Zn^(2+)` keeps on increasing while the concentration of `Cu^(2+)` keeps on decreasing . At the same time voltage os he cell deeps on decreasing . When there is no cahange in concentration of `Cu^(2+) ` and ` Zn^(2+) ` ions, voltmeter gives zero reading and this .

Discussion

1872.	When during electrolusis of a solution of `AgNO_3, 9650` coulmbs of charge pass through the electroplationg bath, the mass of silver deposited on the cathode will be:A. ` 1.08 g`B. ` 10 . 8 g`C. ` 21,. 6g`D. `108 g`
Answer» Correct Answer - B `Ag^+ overset(+e^-)(rarr)` to `Ag, 96500 C` will liberate silver ` =808 g. 96500 C` will liberated silver ` =10.8 g`.

Discussion

1873.	Select the incorrect statement for a dry cell:A. `Mn` is reducded from `+4` to `+3` stateB. `NH_(3)` gas is liberateed outC. `Zn` is used as anodeD. A paste of `NH_(4)Cl` and `ZnCl_(2)`
Answer» Correct Answer - B `NH_(3)` produced due to cathodic reaction. `MnO_(2) + NH_(4)^(+) + e rarr MNO(OH) + NH_(3)` Combines with `Zn^(2+)` to form `Zn(NH_(3))_(4)^(2+)`

Discussion

1874.	What will be the emf of given cell - `Pt \|H_(2) (P_(1)) \| H_((aq))^(+) \| \| H_(2)(P_(2)) \|Pt` ?A. `(RT)/(2F) "log"_(e) (P_(1))/(P_(2))`B. `(RT)/(F) "log"_(e) (P_(1))/(P_(2))`C. `(RT)/(F) "log"_(e) (P_(2))/(P_(1))`D. `(RT)/(2F) "log"_(e)(P_(2))/(P_(1))`
Answer» Correct Answer - A At anode , `H_(2)(P_(1)) to 2 H^(+) + 2e^(-)` At cathode ` 2 H^(+) + 2e to H_(2)(P_(2))` `E_("cathode") = (-RT)/(2F) "ln" (P_(2))/([H^(+)]^(2))` and `E_("anode") = (-RT)/(2F) "ln" ([H^(+)]^(2))/(P_(1))`

Discussion

1875.	Which of the following statement is correct ?A. `E_(cell)` and `Delta_(r)G` of cell reaction both are extensive properties.B. `E_(cell)` and `Delta_(r)G` of cell reaction both are intensive proporties.C. `E_(cell)` is an intensive property while `Delta_(r)G` of cell reaction is an extensive property.D. `E_(cell)` is an intensive property while `Delta_(r)G` of cell reaction is an intensive property.
Answer» Correct Answer - C (c ) is the correct statement.

Discussion

1876.	The unit of cell constant is(a) ohm-1cm-1(b) cm(c) ohm-1 cm(d) cm-1
Answer» The answer is (d) cm^-1

Discussion

1877.	Consider the reactionCr2O72- + 14H+ + 6e– → 2Cr3+ + 7H2OWhat is the quantity of electricity in coulombs needed to reduce 1 mol of Cr2O72-
Answer» According to equation for the reduction of one mole of Cr₂O₇^2-, 6 mole of electrons are needed. Hence the amount of electricity require = 6F = 6 x 96500 C = 579000 C

Discussion

1878.	Which of the following is not a conductor?(a) Cu(metal)(b) NaCl(aq)(c) NaCl(molten)(d) NaCl(solid)
Answer» (d) NaCl_(solid)

Discussion

1879.	Why does the conductivity of solution decreases with dilution?
Answer» The conductivity of a solution is directly proportional to number of ions present in a unit volume of the solution because current is carried forward by the ions. With dilution number of ions in unit volume decreases so that conductivity also decreases. Hence with dilution conductivity decreases. Conductivity of a solution is the conductance of ions present in a unit volume of the solution. On dilution, the number of ions per unit volume decreases. Hence the conductivity decreases.

1879.

Why does the conductivity of solution decreases with dilution?

Answer»

The conductivity of a solution is directly proportional to number of ions present in a unit volume of the solution because current is carried forward by the ions. With dilution number of ions in unit volume decreases so that conductivity also decreases. Hence with dilution conductivity decreases.

Conductivity of a solution is the conductance of ions present in a unit volume of the solution. On dilution, the number of ions per unit volume decreases. Hence the conductivity decreases.

Discussion

1880.	If conductance and conductivity of a cell are equivalent then cell constant will be :(a) 1(b) 0(c) 10(d) 1000
Answer» The answer is (a) 1

Discussion

1881.	The molar conductivity of 0.025 mol L-1 methanoic acid is 46.1 S cm2 mol-1. Calculate its degree of dissoiation and dissociation constant. Given ∧°m(H+) = 349.6 S cm2 mol-1 and ∧°m(HCOO–) = 546 S cm2 mol-1?
Answer» ∧°_m (HCOOH^–)= ∧°_m(H⁺) + ∧°_m (HCOO^–) = 349.6 + 54.6 = 404.2 S cm²mol^-1

Discussion

1882.	The unit of conductivity (specific conductance) is:(a) ohm-1(b) ohm-1 cm-1(c) ohm-1 cm2 equiv-1(d) ohm-1 cm2
Answer» (b) ohm^-1cm^-1

Discussion

1883.	Suggest a way to determine the ∧°m(HCl) – ∧°m(NaCl)
Answer» At infinite dilution, the limiting molar concentration of water ∧°_m( H₂O ) can be calculated by knowing the molar concentration of sodium hydroxide, hydrochloric acid and sodium chloride at infinite dilution. ∧°_m(H₂O) = ∧°_m(HCl) + ∧°_m(NaOH) – ∧°_m(NaCl)

Discussion

1884.	Which statement will be correct for the cell made up of zinc and copper on the basis of electro chemical series?(a) Zinc will act as cathode and copper as anode.(b) Zinc will act as anode and copper as cathode.(c) The flow of electrons takes place from copper to zinc.(d) Copper electrode dissolves and zinc is deposited at zinc electrode.
Answer» (b) Zinc will act as anode and copper as cathode.

Discussion

1885.	How many coulomb charge will required for oxidation of one mole H2O into O2(a) 1.93 x 105 C(b) 9.65 x 104 C(c) 6.023 x 1023 C(d) 4.825 x 104 C
Answer» (b) 9.65 x 10⁴C

Discussion

1886.	If redox reaction takes place in cell then electromotive force (e.m.f.) of cell will be:(a) positive(b) negative(c) zero(d) one
Answer» The answer is (a) positive

Discussion

1887.	Which layer is electroplated at iron sheet?(a) C(b) Cu(c) Zn(d) Ni
Answer» The answer is (c) Zn

Discussion

1888.	When lead storage cell discharge, then(a) SO2 evolves(b) Pb SO4 destroys(c) Pb forms(d) H2SO4 destroys
Answer» (d) H₂SO₄ destroys

Discussion

1889.	If 54 g of silver is deposited during an electrolysis reaction, how much aluminium will be deposited by the same amount of electric current?A. 2.7 gB. 4.5 gC. 27 gD. 5.4 g
Answer» Correct Answer - B 1 F deposits 108 g of Ag `(Ag^(+) + e^(-) to Ag )` 54 g of Ag will be deposited by `1/108xx54=1/2F` 3 F deposite 27 g of Al (`Al^(3+) + 3e^(-) to Al`) `1/2F` will deposit `27/3xx1/2`=4.5 g of Al

Discussion

1890.	An electric current is passed through silver nitrate solution using silver electrodes. 15.28 g of silver was found to be deposited on catode. What will be the weight of copper deposited on cathode if same amount of electricity is passed through copper sulphate solution using copper electrodes?A. 4.49 gB. 6.4 gC. 12.8 gD. 3.2 g
Answer» Correct Answer - A Equivalent wt. of Ag=108/1=108 Equivalent wt. of Cu=63.5/2=31.75 `"Eq. wt. of Ag"/"Eq. wt. of Cu"="Mass of Ag deposited"/"Mass of Cu deposited "` `108/31.75=15.28/W rArr W=(15.28xx31.75)/108`=4.49 g

Discussion

1891.	Which of the following mixture represents rusting of iron?(a) FeO and Fe(OH)3(b) FeO and Fe(OH)2(c) Fe2O3 and Fe(OH)3(d) Fe3O4 and Fe(OH)2
Answer» (c) Fe₂O₃ and Fe(OH)₃

Discussion

1892.	What will be the weight of silver deposited, if `96.5 A` of current is passed into aqueous solution of `AgNO_(3)` for 100 s?A. 1.08 gB. 10.8 gC. 108 gD. 1080 g
Answer» Correct Answer - B `Q=it=96.5xx100=9650 C` `96500 C` deposited weight of `Ag=108 g` `9650 C` deposited weight of `Ag=(108xx9650)/(96500)=10.8 g`

Discussion

1893.	Explain how rusting of iron is considered as setting up of an electrochemical cell.
Answer» In rainy season and in highly humid atmosphere the iron surface has a layer of water. This water layer dissolves acidic oxides of the air like CO₂, SO₂ etc. to form acids which dissociate to give H⁺ ions. H₂O + CO₂ → H₂CO₃ ⇌ 2H⁺ + CO₃²⁺ In the presence of H⁺ ions, iron starts losing electrons at some spot to form ferrous ions, i.e., its oxidiation takes place. Here it is anode. Fe_(s) → Fe²⁺_(aq) + 2e^–_(anode) Now the released electrons move through the metal and reach to another spot where H⁺ ions and the dissolved oxygen take up these electrons and reduction reaction takes place. Here it is cathode. O_2(g) + 4H⁺_(aq) + 4e^– + 2H₂O_(l)(cathode) The overall reaction is 2Fe_(s) + O_2(g) + 4H⁺_(aq) → 2Fe²⁺_(aq) + 2H₂O_(l) Thus in this way an electrochemical cell is set up on the surface. This ferrous ion further oxidised by the atmospheric oxygen to ferric ions which combine with water molecules to from hydrated ferric oxide, Fe₂O₃+ H₂O, which is rust.

Discussion

1894.	Given the standard electrode potentialsK+/K = – 2.93 V, Ag+/Ag = 0.80 VHg22+/Hg = 0.79V, Mg2+/Mg = – 237V, Cr2+/Cr = – 0.74 VArrange these metals in their increasing order of reducing power.
Answer» Higher the oxidation potential, more easily it is oxidized and hence greater is the reducing power. Thus increasing order of reducing power will be Ag < Hg < Cr < Mg

Discussion

1895.	When, during electrolysis of a solution of `AgNO_(3) 9650` colombs of charge pass through the electroplating path, the mass of silver deposited on the cathode will be:A. 1.08gB. 10.8gC. 21.6gD. 108g.
Answer» Correct Answer - B `Ag^(+)+e^(-)rarrAg^(-)` 96500C 108g (1mol) (1 mol) `therefore 96500C` deposit `Ag=10.8g`

Discussion

1896.	Carefully observe the given figure and using data provided find the `EMF` of shown Galvenic cell in volt: Solution A is `0.1M` each in `NH_(4)OH` and `NH_(4)CI` and solution B is `0.1M` each in `CH_(3)COOH` and `CH_(3)COONa^(+)`. [Given: `K_(a)(CH_(3)COOH) = 10^(-5), K_(b) (NH_(4)OH) = 10^(-5)` and `(2.303RT)/(F) = 0.06` volt]
Answer» Correct Answer - `0.24` `pH` of solution (A) : Solution A is a basic Buffer `pOH = pK_(b) +log.(["Salt"])/([Base]) rArr pOH = 5` `rArr pH = 9 rArr [H^(+)]_(A) = 10^(-9)M` `pH` of solution (B): Solution B is Acidic Buffer `pH = pK_(a) + (["Salt"])/([Base])` `rArr pH = 5 +log.((0.1))/((0.1)) rArr pH = 5` `rArr [H^(+)]_(B) = 10^(-5)` Now, The cell is a concentration cell Cell reaction: `2H_(B)^(+)(aq) +2e hArr H_(2,B)(g)` `H_(2,A) (g) hArr 2H_(A)^(+) +2e` `bar(2H_(B)^(+)(aq)+H_(2,A)(g)overset(n=2)hArr)2H_(A)^(+)(aq)+H_(2,B)(g)` Nernst Equation for cell `E_(cell) = 0-(0.06)/(2) log.([H^(+)]_(A)^(2))/([H^(+)]_(B)^(2))` `=0.06 log ((10^(-4))/(1))rArr +0.24` volt.

Discussion

1897.	Consider the following reaction, `Cu\|Cu^(2+) (1M)\|\|(Zn^(2+)(1 M)\|Zn` A cell represented above should have emfA. positiveB. negativeC. zeroD. Cannot be predicted
Answer» Correct Answer - B If `E_(red)^(@)` of `Cu` and `Zn` are known from `ECS`. then, `E^(@)=E_("cathode")^(@)-E_("anode")^(@)` `=E_("right")^(@)-E_("left")^(@)` `=(-0.76)-(+0.34)` (From ECS) `=-0.76-0.34=-1.10 V`

Discussion

1898.	For the redox reaction: `Zn(s) +Cu^(2+) (0.1M) rarr Zn^(2+) (1M)+Cu(s)` taking place in a cell, `E_(cell)^(@) is 1.10` volt. `E_(cell)` for the cell will be `(2.303 (RT)/(F) = 0l.0591)`A. `1.07` voltB. `0.82` voltC. `2.14` voltD. `1.80` volt
Answer» Correct Answer - A Applying Nernst equation `E_(cell) = E_(cell)^(@) =- (0.0591)/(2)log. \|(Sn^(2+))/(Cu^(2+))\|` `=1.1 -(0.0591)/(2)log.(1)/(0.1)` `1.1 - 0.02955` `=1.07`

Discussion

1899.	The emf of a galvanic cell is positive when free energy change of reaction isA. `gt 0`B. `lt 0`C. `= 0`D. has a very large value .
Answer» Correct Answer - B `Delta G^(@) = - nFE_("cell")^(@)` . Hence , if `E_("cell")^(@)` is positive , then `DeltaG^(@)` is negative .

Discussion

1900.	Which of the following will be able to react with dilute HCl to give hydrogen gas?A. CuB. MgC. HgD. `Ag`.
Answer» Correct Answer - B Mg lies above `H_(2)` in the activity series `Mg+2H^(+)rarrMg^(2+)+H_(2)` has positive Emf.

Discussion

Explore topic-wise InterviewSolutions in .

Calomel is the name ofA. HgB. `Hg_(2) Cl_(2)`C. `Hg + Hg_(2) Cl_(2)`D. `HgCl_(2)`

The electric conduction of a salt solution in water depends on the :A. size of its moleculesB. shape of its moleculesC. size of solvent moleculesD. extent of its ionization

Electrode potential for Mg electrode varies according to the equation `E_(Mg^(2+)//Mg)=E_(Mg^(2+)|Mg)^(Theta)-(0.059)/(2)"log"(1)/([Mg^(2+)])` The graph of `E_(Mg^(2+)|Mg)` vs log `[Mg^(2+)]` isA. B. C. D.

When calomel electrode acts as an anode then the reaction isA. `2 Hg + 2 Cl^(-) to Hg_(2) Cl_(2) + 2e^(-)`B. `Hg_(2) Cl_(2) to 2 Hg^(+) + Cl_(2) + 2e^(-)`C. `Hg_(2) Cl_(2) + 2e ^(-) to 2 Hg + Cl_(2)`D. `Hg_(2) Cl_(2) + 2e^(-) to 2 Hg + 2 Cl^(-)`

The electric conduction of a salt solution in water depends on the :A. shape of moleculesB. size of its moleculesC. size of solvent moleculesD. extent of its ionisation

Which of the following reaction is possible at the angle?A. `2Cr^(2+)+7H_(2)OrarrCr_(2)O_(7)^(2-)+14H^(+)`B. `F_(2)rarr2F^(-)`C. `(1)/(2)O_(2)+3H^(+)rarrH_(2)O`D. None of these

A decinormal calomel electrode containsA. N/10 solution of `Hg_(2) Cl_(2)`B. 1 N solution of HClC. 1 N solution of `Hg_(2) Cl_(2)`D. N/10 solution of KCl

In electroplating, the article to be electoplated serves as:A. cathodeB. electrolyteC. anodeD. conductor

What mass of zinc can be produced by the electrolysis of zinc sulphate solution when a steady current of 0.015 ampere is passed for 15 minutes ? Given that atomic mass of zinc is 65.4 amu ?

A current of 1.40 ampere is passed through 500 mL of 0.180 M solution of zinc sulphate for 200 seconds. What will be the molarity of `Zn^(2+)` ions after deposition of zinc?A. 0.154 MB. 0.177 MC. 2 MD. 0.180 M

How much time is required to deposit `1xx10^(-3)` cm thick layer of silver (density is 1.05 g `cm^(-3)` ) on a surface of area 100 `cm^2` by passing a current of 5 A through `AgNO_3` solution?A. 125 sB. 115 sC. 18.7 sD. 27.25 s

What will be the emf for the given cell ? `Pt|H_(2)(g,P_(1))|H^(+)(aq)|H_(2)(g,P_(2))|Pt`A. `(RT)/(F)In(p_(1))/(p_(2))`B. `(RT)/(2F)In(p_(1))/(p_(2))`C. `(RT)/(F)In(p_(1))/(p_(2))`D. None of these.

How much metal will be deposited when a current of 12 ampere with 75% efficiency is passed through the cell for 3 h? (Given: Z= `4xx10^(-4)` )A. 32.4 gB. 38.8 gC. 36.0 gD. 22.4 g

When during electrolusis of a solution of `AgNO_3, 9650` coulmbs of charge pass through the electroplationg bath, the mass of silver deposited on the cathode will be:A. ` 1.08 g`B. ` 10 . 8 g`C. ` 21,. 6g`D. `108 g`

Select the incorrect statement for a dry cell:A. `Mn` is reducded from `+4` to `+3` stateB. `NH_(3)` gas is liberateed outC. `Zn` is used as anodeD. A paste of `NH_(4)Cl` and `ZnCl_(2)`

What will be the emf of given cell - `Pt |H_(2) (P_(1)) | H_((aq))^(+) | | H_(2)(P_(2)) |Pt` ?A. `(RT)/(2F) "log"_(e) (P_(1))/(P_(2))`B. `(RT)/(F) "log"_(e) (P_(1))/(P_(2))`C. `(RT)/(F) "log"_(e) (P_(2))/(P_(1))`D. `(RT)/(2F) "log"_(e)(P_(2))/(P_(1))`

The unit of cell constant is(a) ohm-1cm-1(b) cm(c) ohm-1 cm(d) cm-1

Consider the reactionCr2O72- + 14H+ + 6e– → 2Cr3+ + 7H2OWhat is the quantity of electricity in coulombs needed to reduce 1 mol of Cr2O72-

Which of the following is not a conductor?(a) Cu(metal)(b) NaCl(aq)(c) NaCl(molten)(d) NaCl(solid)

Why does the conductivity of solution decreases with dilution?

If conductance and conductivity of a cell are equivalent then cell constant will be :(a) 1(b) 0(c) 10(d) 1000

The molar conductivity of 0.025 mol L-1 methanoic acid is 46.1 S cm2 mol-1. Calculate its degree of dissoiation and dissociation constant. Given ∧°m(H+) = 349.6 S cm2 mol-1 and ∧°m(HCOO–) = 546 S cm2 mol-1?

The unit of conductivity (specific conductance) is:(a) ohm-1(b) ohm-1 cm-1(c) ohm-1 cm2 equiv-1(d) ohm-1 cm2

Suggest a way to determine the ∧°m(HCl) – ∧°m(NaCl)

How many coulomb charge will required for oxidation of one mole H2O into O2(a) 1.93 x 105 C(b) 9.65 x 104 C(c) 6.023 x 1023 C(d) 4.825 x 104 C

If redox reaction takes place in cell then electromotive force (e.m.f.) of cell will be:(a) positive(b) negative(c) zero(d) one

Which layer is electroplated at iron sheet?(a) C(b) Cu(c) Zn(d) Ni

When lead storage cell discharge, then(a) SO2 evolves(b) Pb SO4 destroys(c) Pb forms(d) H2SO4 destroys

If 54 g of silver is deposited during an electrolysis reaction, how much aluminium will be deposited by the same amount of electric current?A. 2.7 gB. 4.5 gC. 27 gD. 5.4 g

Which of the following mixture represents rusting of iron?(a) FeO and Fe(OH)3(b) FeO and Fe(OH)2(c) Fe2O3 and Fe(OH)3(d) Fe3O4 and Fe(OH)2

What will be the weight of silver deposited, if `96.5 A` of current is passed into aqueous solution of `AgNO_(3)` for 100 s?A. 1.08 gB. 10.8 gC. 108 gD. 1080 g

Explain how rusting of iron is considered as setting up of an electrochemical cell.

Given the standard electrode potentialsK+/K = – 2.93 V, Ag+/Ag = 0.80 VHg22+/Hg = 0.79V, Mg2+/Mg = – 237V, Cr2+/Cr = – 0.74 VArrange these metals in their increasing order of reducing power.

When, during electrolysis of a solution of `AgNO_(3) 9650` colombs of charge pass through the electroplating path, the mass of silver deposited on the cathode will be:A. 1.08gB. 10.8gC. 21.6gD. 108g.

Consider the following reaction, `Cu|Cu^(2+) (1M)||(Zn^(2+)(1 M)|Zn` A cell represented above should have emfA. positiveB. negativeC. zeroD. Cannot be predicted

For the redox reaction: `Zn(s) +Cu^(2+) (0.1M) rarr Zn^(2+) (1M)+Cu(s)` taking place in a cell, `E_(cell)^(@) is 1.10` volt. `E_(cell)` for the cell will be `(2.303 (RT)/(F) = 0l.0591)`A. `1.07` voltB. `0.82` voltC. `2.14` voltD. `1.80` volt

The emf of a galvanic cell is positive when free energy change of reaction isA. `gt 0`B. `lt 0`C. `= 0`D. has a very large value .

Which of the following will be able to react with dilute HCl to give hydrogen gas?A. CuB. MgC. HgD. `Ag`.