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NEET Chemistry MCQ
Redox Reactions And Electro Chemistry Mcq
Quiz 7
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Q.1
The standard oxidation potential of zinc and silver in water at 298K are Zn(s) → Zn2+(aq) +2e- . 0.76V Ag(s) → Ag+ + e- , -0.80 V Which of the following reactions actually takes place? [ NCERT 1983]
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a)Zn(s) + 2Ag+(aq) → Zn2+(aq) + 2Ag(s)
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b) Zn2+ +2Ag(s) → 2Ag+(s) + Zn(s)
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c)Zn(s)+ Ag(s) → Zn2+(aq) + Ag+(aq)
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d)Zn2+(aq) + Ag+(aq) → Zn(s) + Ag(s)
Explanation
Answer: (a)
Q.2
Molar ionic conductivity of a bi-bivalent electrolyte are 57 andThe molar conductivity of the solution will be [ DPMT 2002]
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a) 130 S cm2 mol-1
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b) 65 S cm2 mol-1
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c)260 S cm2 mol-1
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d)187 S cm2 mol-1
Explanation
Salt is A2+B2- Λ=57 +73=130 S cm2 mol-1Answer: (a)
Q.3
E.M.F of cell is measured by .. [ KCET 1984]
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a) Voltmeter
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b) potentiometer
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c)galvanometer
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d)ammeter
Explanation
Answer:(b)
Q.4
If 0.01M solution of an electrolytic has a resistance of 40 Ohms in a cell having cell constant of 0.4 cm- then its molar conductance in ohm- cm2 mol- will be [ CBSE PMT 1996]
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a) 104
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b) 103
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c) 102
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d) 10
Explanation
Use formula κ=Cell constant / R and formula Answer: (b)
Q.5
A solution containing one mole per litre of each Cu(NO3)2, AgNO3, Hg2(NO3)2 and Mg(NO3)2 is being electrolysed by using inert electrodes. the values of standard electric potentials in volts ( reduction potentials) are Ag/Ag+=0.80, 2Hg/Hg22+=0.79 Cu/Cu2+=0.34, Mg/Mg2+=-2.37 With increasing voltage, the sequence of deposition of metals on the cathod will be .. [ IIT 1984]
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a)Ag, Hg, Cu, Mg
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b) Mg, Cu, Hg, Ag
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c)Ag, Hg, Cu
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d)Cu, Hg, Ag
Explanation
Higher the reduction potential, more easily is the metal deposited But Mg will not deposited as H2O will be reduced more easily than Mg2+ ionsAnswer: (c)
Q.6
A solution of sodium sulphate in water is electrolysed using inert electrodes. the products at the cathode and anode are respectively .. [ IIT 1987]
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a) H2, O2
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b) O2, H2
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c)O2, Na
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d)O2, SO4
Explanation
At cathode , H2O is more easily reduce than Na+ to hive H2At anode H2, H2O is easily oxidised than SO4- to give O2Answer: (a)
Q.7
The resistance of 0.1N solution of a salt is found to be 2.5×103 ohms. The equivalent conductance of the solution is (cell constant=1.15 cm-1) [ Manipal PMT 2001]
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a) 4.6
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b) 5.6
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c)6.6
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d)7.6
Explanation
USe formula κ=G × cell constant and equation Answer:(a)
Q.8
How many c.c. of oxygen will be liberated by 2 amp current flowing for 3 minutes and 13 second through acidulated water? [ AFMC 1981]
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a) 11.2 c.c
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b) 33.6 c.c.
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c) 44.8 c.c.
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d) 22.4 c.c.
Explanation
total time 3 min 13sec=193 sec Current=2 amp Charge Q=It=2×193 sec=386 C 96500C=8gm of Oxygen(O) Since 8gm of O=1/4 moles of O2=22.4/4 L=5.6 L 386 C=? L 0.0244 L=.0224 × 1000=22.4 c.c Answer: (d)
Q.9
the electric charge for electrode deposition of one gram equivalent of substance is ..[IIT 1984]
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a) One ampere for one second
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b) 96500 coulombs per second
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c) charge on one mole of electrons
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d) One ampere for one hour
Explanation
One gram equivalent is deposited by 1F. i.e charge on one mole of electrons Answer: (c)
Q.10
Specific conductance of 0.1M Nitric acid is 6.3 × 10-2 ohm-1cmthe molar conductance of the solution is
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a) 630 ohm-1 cm2
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b) 315 ohm-1 cm2
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c) 100 ohm-cm2
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d) 6300 ohm-1cm2
Explanation
Use formula Answer: (a)
Q.11
The reference calomel electrode is made from which of the following? [ MP 2002]
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a) ZnCl2
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b) CuSO4
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c) Hg2Cl2
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d) HgCl2
Explanation
Answer:(c)
Q.12
On passing 1 F of electricity through the electrolytic cells containing Ag+, Ni2+, Cr3+ ions solution, the deposited Ag( At wt = 108), Ni(At wt. = 59) and Cr(At. wt. =52) are . . . . respectively [ AIIMS 1982]
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a) 108.0 gm, 29.5gm , 17.3 gm
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b) 108.0gm, 59.0gm, 52.0gm
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c) 108.0gm, 108.0gm, 108.0gm
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d) 108.0gm, 117.5gm, 166.0gm
Explanation
1F will deposit 1gram equivalent of each Gram equivalent weight = Atomic weight/ valency Ag = 108/1 = 108 gram Ni = 59/2 = 29.5 gram Cr = 52/3 = 17.3 gram Answer: (a)
Q.13
The amount of ion discharged during electrolysis is not directly proportional to [ NCERT 1983]
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a)Resistance
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b) Time
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c)Current
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d)Chemical equivalent of ion
Explanation
Answer: (a)
Q.14
The equivalent conductance of NaCl, HCl and C2H5COONa at infinite dilution are 126.45, 426.16 and 91 ohm-1 cmThe equivalent conductance of C2H5COOH is
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a) 201.28 ohm-1cm2
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b) 390.71-1cm2
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c)698.28-1cm2
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d)540.48-1cm2
Explanation
Λo(C2H5COOH)=Λo(C2H5COONa) + Λo (HCL) - Λo(NaCl)=91 +426.16 -126.45=390.71 ohm-1cm2Answer: (b)
Q.15
An electrolyte is one [ KCET 1984]
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a) which conducts electric current in any solvent
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b) which is capable of ionisation by passing current
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c)which dissociates into ions by dissolving in a suitable solvent
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d)non of the above
Explanation
Answer:(c)
Q.16
The cell constant of given cell is 0.47cm-. the resistance of solution place in this cell is measured to be 31.6 ohm. The conductivity of the solution ( in Scm-) is [ Pb CET 1995]
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a) 0.15
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b) 1.5
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c) 0.015
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d) 150
Explanation
κ=G × cell constant κ=cell constant/ R κ=0.47/31.6=0.015 S cm-1 Answer: (c)
Q.17
When electric current is passed through a cell having an electrolyte, the positive ions move towards the cathode and the negative ions towards the anode. if the cathode is pulled out of the solution [ AIIMS 1980]
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a)the positive and negative ions will move towards the anode
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b) the positive ions will start moving towards the anode, the negative ions will stop moving
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c)the negative ions will continue to move towards anode; the positive ions will stop moving
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d)the positive and negative ions will start moving randomly
Explanation
When anode or cathode is pulled out circuit is broken and current will not flow thus ions will move randomly Answer: (d)
Q.18
An electrolyte cell contains a solution of Ag2SO4 and has platinum electrodes. A current is passed until 1.6gm of O2 has been liberated at anode. The amount of silver deposited at cathode would be. [ CPMT 1996]
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a) 107.88 gm
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b) 1.6 gm
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c)0.8 gm
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d)21.6 gm
Explanation
Four moles of electrons releases one mole of oxygen=32 gm1.6 gm oxygen requires 1/5 moles of electronsThus gram equivalent of Ag released=1/5=108/5 gm=21.6 gmOR Answer: (d)
Q.19
THe specific conductivity of N/10 KCl solution at 20°C is 0.0212 ohm-cm- and the resistance of the cell containing this solution at 20°C is 55ohm. The cell constant is ..[AIIMS 1999]
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a) 4.616 cm-1
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b) 1.166 cm-1
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c)2.1736 cm-1
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d)3.324 cm-1
Explanation
Use formula κ=cell constant /R Answer:(b)
Q.20
The reaction ½ H2(g) + AgCl(s) → H+(aq) + Cl-(aq) + Ag(s) occurs in the galvanic cell [IIT 1985]
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a) Ag|AgCl(s)|KCl(aq)|AgNO3(aq)|Ag
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b) Pt|H2(g)|HCl(aq)|AgNO3(aq)|Ag
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c) Pt|H2(g)|HCl(aq)|AgCl(s)|Ag
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d) Pt|H2(g)|KCl(aq)|AgCl(s)|Ag
Explanation
H2 undergo oxidation and AgCl undergo reduction Answer: (c)
Q.21
other things being equal, the EMF of Daniel cell may be increased by [ Pb. CET 1988]
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a)keeping low temperature
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b) using large copper electrodes
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c)Using large zinc electrodes
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d)decreasing concentration of Cu2+ ions
Explanation
By decreasing the temperature or by increasing Cu2+ e.m.f. of cell can be increasedAnswer: (a)
Q.22
A solution of CuSO4 is electrolysed for 7 minutes with a current of 0.6amp. The amount of electricity passed is equal to [ Pb CET 1991]
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a) 4.2 coulombs
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b) 2.6 ×10-3 faraday
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c)126 coulombs
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d)35 coulombs
Explanation
Charge Q=It Q=0.6 ×(7×60)=252 C In faraday=252/96500=2.6 ×10-3 FaradayAnswer: (b)
Q.23
A certain quantity of electricity is passed through an aqueous solution of AgNO3 and cupric salt solution connected in series. the amount of ga deposited in 1.08gm, then the amount of copper deposited is (At wt. Cu=63.5, Ag=108) [ EAMCET 1986]
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a) 0.6454 g
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b) 6.354 g
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c)0.3177 g
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d)3.177g
Explanation
Valancy of Ag=1 thus to deposit 1.08gm of Ag electric charge is F/100 Now 2F charge deposit one mole of Cu=63.5 gm F/100 charge will deposited cu of 1/200 mole=63.5/200=0.3177 gm Answer:(c)
Q.24
Which of the following metals can deposited copper from copper sulphate solution? [ MP 1989]
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a) Mercury
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b) Iron
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c) Gold
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d) Platinum
Explanation
negative reduction potential of Fe is more than Cu Answer: (b)
Q.25
If same amount of electricity is passed through aqueous solution of AgNO3 and CuSO4 and the number of Ag and Cu atoms deposited are x and y respectively. then [ Pb. CET 1988]
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a)x=y
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b) x < y
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c)y=2x
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d)x=2y
Explanation
Ag+ + e- → Ag,Cu2+ + 2e2- → CuAnswer: (d)
Q.26
The cathode in a galvanic cell and electrolytic cell is [ Pb CET a990]
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a) Negatively charged in both cases
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b) Positively charged in both cases
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c)positively charged in galvanic cell but negatively charged in an electrolytic cell
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d)Negatively charged in a galvanic cell but positively charged in an electrolytic cell
Explanation
Answer: (c)
Q.27
On the electrolysis of acidic water, if volume of hydrogen liberated is 5.6cm3, then the volume of oxygen liberated is equal to [ Pb CET 1988]
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a) 2.8 cm2
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b) 5.6 cm3
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c)8.4 cm3
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d)11.2 cm3
Explanation
Hydrogen liberated is twice the volume of Oxygen gas Answer:(a)
Q.28
From the solution of an electrolyte, one mole of electron will deposited at cathode.. [ CPMT 1997]
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a) 63.5 gm of Cu
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b) 24.0 gm of Mg
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c) 11.5 gm of Na
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d) 9.0 gm of Al
Explanation
One mole of electron=1F will deposited 1 gram equivalence Answer: (d)
Q.29
When a copper wire is placed in a solution of AgNO3 , the solution acquires blue colour. this is due to the formation of [ Roorkee 1989][
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a)Cu2+ ions
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b) Cu+ ions
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c)Soluble complex of copper with AgNO3
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d)Cu- ion by the reduction Cu
Explanation
Cu + 2Ag+ → Cu2+ + 2AgAnswer: (a)
Q.30
A current of 9.65 ampere flowing for 10 minutes deposits 3.0 g of the metal which is nonvalent. the atomic mass of the metal is ..{BHU 1989]
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a) 10
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b) 50
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c)30
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d)96.5
Explanation
Charge=It=9.65 ×10 × 60=0.06F 1F deposit 1 gram equivalent=Atomic weight / Valency=Atomic weight As given monovalent 0.06 F will deposit 0.06 gram equivalence=0.06 Atomic weight 0.06 × M=3 ∴ M=3/0.06=50 Answer: (b)
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