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Hydrogen

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Question
CBSEENCH11008254
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A hydrogen gas electrode is made by dipping platinum wire in a solution of HCl of pH =10 and by passing hydrogen gas through the platinum wire at 1 atm pressure. The oxidation potential of electrode would be

  • 0.0591 V

  • 0.59 V

  • 0.118 V

  • 1.18 V

Solution

B.

0.59 V

For Hydrogen electrode, oxidation half reaction is
stack straight H subscript 2 space with 1 space atm below rightwards arrow stack 2 straight H to the power of plus with left parenthesis at space pH space 10 right parenthesis below space plus 2 straight e to the power of minus If space pH space equals space 10 straight H to the power of plus space equals space 1 space straight x space 10 to the power of negative pH end exponent space equals space 1 space straight x 10 to the power of negative 10 end exponent From space nernst space equation comma straight E subscript cell space equals space straight E subscript cell superscript 0 space minus fraction numerator 0.0591 over denominator 2 end fraction space log space fraction numerator left square bracket straight H to the power of plus right square bracket squared over denominator straight p subscript straight H subscript 2 end subscript end fraction For space hydrogen space electrode comma space straight E subscript cell superscript 0 space equals space 0 straight E subscript cell space equals negative fraction numerator 0.0591 over denominator 2 end fraction space log space fraction numerator left parenthesis 10 to the power of negative 10 end exponent right parenthesis squared over denominator 1 end fraction 0.0591 space straight x space log space 10 to the power of 10 0.0591 space straight x space 10 space equals space 0.591 space straight V

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Question
CBSEENCH11008375
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Some statement about heavy water are given below

A) Heavy water is used as a moderator in nuclear reactors.

B) Heavy water is more associated than ordinary water.

C) Heavy water is more effective solvent than ordinary

  • A and B

  • A, B and C

  • B and C

  • A and C

Solution

A.

A and B

Heavy water is used as a moderator in nuclear reactors. Its boiling point is higher as compared to the ordinary water. Thus, it is more associated as compared to ordinary water. The dielectric constant is however higher for H2O, thus, H2O is a more effective solvent than heavy water (D2O).

Question
CBSEENCH11008247
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The reaction of aqueous KMnO4 with H2O2 in acidic conditions gives.

  • Mn4+ and O2

  • Mn2+ and O2

  • Mn2+ and O3

  • Mn4+ and MnO2

Solution

B.

Mn2+ and O2

The reaction of aqueous KMnO4 with H2O2 in acidic medium is 
3H2SO4 + KMnO4 +5 H2O2 --> 5O2 +2MnSO4 +8H2O +K2SO4
In the reaction, KMnO4 oxidise H2O2 to O2 and itself [MnO4-] gets reduced to Mn2+ ions as MnSO4. Hence, aqueous solution of KMnO4 with H2O2 yields Mn2+ and O2 in acidic conditions.

Question
CBSEENCH11008233
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Which of the following statement about hydrogen is incorrect?

  • Hydrogen never acts as cation in ionic salts

  • Hydronium ion, H3O+ exist freely in solution

  • Dihydrogen does not act as a reducing agent

  • Hydrogen has three isotopes of which tritium is the most common

Solution

C.

Dihydrogen does not act as a reducing agent

We can have both answers (C, D) 
For ionic salts, hydrogen never behaves as cation, but behaves as anion (H-)
H3O+ exist freely in solution
Dihydrogen acts as a reducing agent.
Hydrogen has three isotopes. Protium, Deuterium and Tritium. Protium is the most common isotopes of hydrogen with an abundance of 99.98%.

Question
CBSEENCH11008352
Wired Faculty App

Which one of the following molecular hydrides acts as a Lewis acid? 

  • NH3

  • H2O

  • B2H6

  • CH4

Solution

C.

B2H6

Electron deficient molecules behave as Lewis acid.
Among the given molecules, only diborane is electron deficient, ie, does not have a complete octet. Thus, it acts as a Lewis acid. 
NH3 and H2O being electron rich molecules behave as Lewis base.

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