1
MCQ (Single Correct Answer)

JEE Main 2017 (Online) 8th April Morning Slot

What is the standard reduction potential (Eo) for Fe3+ $$ \to $$ Fe ?
Given that :
Fe2+ + 2e$$-$$ $$ \to $$ Fe; $$E_{F{e^{2 + }}/Fe}^o$$ = $$-$$0.47 V
Fe3+ + e$$-$$ $$ \to $$ Fe2+; $$E_{F{e^{3 + }}/F{e^{2 + }}}^o$$ = +0.77 V
A
$$-$$ 0.057 V
B
+ 0.057 V
C
+ 0.30 V
D
$$-$$ 0.30 V

Explanation

For the given reaction :

Fe3+ + e$$-$$ $$ \to $$ Fe2+; $$E_{F{e^{3 + }}/F{e^{2 + }}}^o$$ = +0.77 V

$$\Delta $$Go = -nFEo

$$ \Rightarrow $$ $$\Delta G_1^o = - \left( 1 \right)F\left( {0.77} \right)$$ = -0.77F

For the following reaction :

Fe2+ + 2e$$-$$ $$ \to $$ Fe; $$E_{F{e^{2 + }}/Fe}^o$$ = $$-$$0.47 V

$$\Delta G_2^o = - \left( 2 \right)F\left( {-0.47} \right)$$ = 0.47$$ \times $$2F

Overall reaction :

Fe3+ + 3e$$-$$ $$ \to $$ Fe;

$$\Delta G_3^o = - 3FE_3^o$$

$$ \Rightarrow $$ $$\Delta G_1^o$$ + $$\Delta G_2^o$$ = $$ 3FE_3^o$$

$$ \Rightarrow $$ -0.77F + 0.47$$ \times $$2F = $$ 3FE_3^o$$

$$ \Rightarrow $$ $$E_3^o = - {{0.17} \over 3}$$ = -0.057 V
2
MCQ (Single Correct Answer)

JEE Main 2017 (Online) 8th April Morning Slot

Consider the following standard electrode potentials (Eo in volts) in aqueous solution :

Element M3+ /M M+ /M
A1 -1.66 + 0.55
T1 +1.26 - 0.34


Based on these data, which of the following statements is correct ?
A
T1+ is more stable than A13+
B
A1+ is more stable than A13+
C
T1 + is more stable than A1+
D
T13+ is more stable than A13+
3
MCQ (Single Correct Answer)

JEE Main 2017 (Online) 9th April Morning Slot

To find the standard potential of M3+/M electrode,the following cell is constituted : Pt/M/M3+(0.001 mol L−1 )/Ag+(0.01 mol L−1 )/Ag

The emf of the cell is found to be 0.421 volt at 298 K. The standard potential of half reaction M3+ + 3e$$ \to $$ M at 298 K will be :

(Given $$E_{A{g^ + }\,/\,Ag}^ - $$ at 298 K = 0.80 Volt)
A
0.38 Volt
B
0.32 Volt
C
1.28 Volt
D
0.66 Volt
4
MCQ (Single Correct Answer)

JEE Main 2018 (Offline)

How long (approximate) should water be electrolysed by passing through 100 amperes current so that the oxygen released can completely burn 27.66 g of diborane?
(Atomic weight of B = 10.8 u)
A
1.6 hours
B
6.4 hours
C
0.8 hours
D
3.2 hours

Explanation

Required reaction :

B2H6 + 3O2 $$ \to $$ B2 O3 + 3 H2 O

Here molar mass of B2H6 =10.8 $$ \times $$ 2 + 6 = 27.6 gm

Given weight of B2H6 = 27.66 g

$$\therefore\,\,\,\,$$No of moles of B2H6 = $${{27.6} \over {27.66}} \simeq 1$$ mole.

For combustion of 1 mole B2H6 3 moles O2 required.

This 3 mole of O2 is obtained by electrolysis of H2O.

2H2O($$l$$) $$ \to $$ O2 (g) + 4 H+ (aq) + 4 e$$-$$

From Faradays law of electrolysis,

moles $$ \times $$ nf = $${{It} \over {96500}}$$

Here moles of O2 = 3.

Nf of O2 = 4 (in H2 change of O = $$-$$2

and in O2 change of 0 = O.

So change in charge = 2 .

for two atoms of O2 change in charge = 2 $$ \times $$ 2 = 4)

$$\therefore\,\,\,\,$$ 3 $$ \times $$ 4 = $${{100 \times t} \over {96500}}$$

$$ \Rightarrow \,\,\,\,$$ t = 12 $$ \times $$ 965 sec.

$$ \Rightarrow \,\,\,\,$$ t = $${{12 \times 965} \over {60 \times 60}}$$ hr

= 3.2 hr

Questions Asked from Electrochemistry

On those following papers in MCQ (Single Correct Answer)
Number in Brackets after Paper Name Indicates No of Questions
AIEEE 2002 (5)
keyboard_arrow_right
AIEEE 2003 (5)
keyboard_arrow_right
AIEEE 2004 (6)
keyboard_arrow_right
AIEEE 2005 (4)
keyboard_arrow_right
AIEEE 2006 (2)
keyboard_arrow_right
AIEEE 2007 (2)
keyboard_arrow_right
AIEEE 2008 (1)
keyboard_arrow_right
AIEEE 2009 (2)
keyboard_arrow_right
AIEEE 2010 (2)
keyboard_arrow_right
AIEEE 2011 (1)
keyboard_arrow_right
AIEEE 2012 (1)
keyboard_arrow_right
JEE Main 2013 (Offline) (1)
keyboard_arrow_right
JEE Main 2014 (Offline) (3)
keyboard_arrow_right
JEE Main 2015 (Offline) (1)
keyboard_arrow_right
JEE Main 2016 (Offline) (1)
keyboard_arrow_right
JEE Main 2016 (Online) 9th April Morning Slot (1)
keyboard_arrow_right
JEE Main 2016 (Online) 10th April Morning Slot (2)
keyboard_arrow_right
JEE Main 2017 (Offline) (1)
keyboard_arrow_right
JEE Main 2017 (Online) 8th April Morning Slot (2)
keyboard_arrow_right
JEE Main 2017 (Online) 9th April Morning Slot (1)
keyboard_arrow_right
JEE Main 2018 (Offline) (1)
keyboard_arrow_right
JEE Main 2018 (Online) 15th April Morning Slot (1)
keyboard_arrow_right
JEE Main 2018 (Online) 16th April Morning Slot (1)
keyboard_arrow_right
JEE Main 2019 (Online) 9th January Morning Slot (1)
keyboard_arrow_right
JEE Main 2019 (Online) 10th January Morning Slot (1)
keyboard_arrow_right
JEE Main 2019 (Online) 10th January Evening Slot (1)
keyboard_arrow_right
JEE Main 2019 (Online) 11th January Morning Slot (1)
keyboard_arrow_right
JEE Main 2019 (Online) 12th January Morning Slot (1)
keyboard_arrow_right
JEE Main 2019 (Online) 12th January Evening Slot (2)
keyboard_arrow_right
JEE Main 2019 (Online) 8th April Morning Slot (1)
keyboard_arrow_right
JEE Main 2019 (Online) 8th April Evening Slot (1)
keyboard_arrow_right
JEE Main 2019 (Online) 9th April Morning Slot (1)
keyboard_arrow_right
JEE Main 2019 (Online) 9th April Evening Slot (1)
keyboard_arrow_right
JEE Main 2019 (Online) 12th April Morning Slot (1)
keyboard_arrow_right
JEE Main 2019 (Online) 12th April Evening Slot (1)
keyboard_arrow_right
JEE Main 2020 (Online) 7th January Morning Slot (1)
keyboard_arrow_right
JEE Main 2020 (Online) 7th January Evening Slot (1)
keyboard_arrow_right
JEE Main 2020 (Online) 4th September Morning Slot (1)
keyboard_arrow_right
JEE Main 2020 (Online) 4th September Evening Slot (1)
keyboard_arrow_right
JEE Main 2020 (Online) 5th September Evening Slot (1)
keyboard_arrow_right
JEE Main 2020 (Online) 6th September Evening Slot (1)
keyboard_arrow_right
JEE Main 2021 (Online) 24th February Morning Slot (1)
keyboard_arrow_right
JEE Main 2021 (Online) 16th March Morning Shift (1)
keyboard_arrow_right
JEE Main 2021 (Online) 26th August Morning Shift (1)
keyboard_arrow_right
JEE Main 2021 (Online) 31st August Evening Shift (1)
keyboard_arrow_right

EXAM MAP

Joint Entrance Examination

JEE Advanced JEE Main

Graduate Aptitude Test in Engineering

GATE CSE GATE EE GATE ECE GATE ME GATE CE GATE PI GATE IN

Medical

NEET