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Consider the reaction: Cr2O72– + 14H+ + 6e- → 2Cr3+ + 8H2O
What is the quantity of electricity in coulombs needed to reduce 1 mol of Cr2O72-?

Answer:

Cr
2O72– → 2Cr3+
2Cr6+ + 6e → 2Cr3+
In given equation there are 6 electrons are required so that n = 6
Use the formula
Required charge      = nF
Plug the values in this formula we get
Required charge      = 6 × 96487 Coulombs
= 578922 Coulombs
= 5.79 × 105 Coulombs
 
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Suggest a list of metals that are extracted electrolytically.

Answer:

The Metals which is at the top of the reactivity series  can extracted electrolytically.
So all alkali metals and some alkaline metals can extracted with this method.
Example Li, Na, K, Mg, Al etc.
193 Views

Write the chemistry of recharging the lead storage battery, highlighting all the materials that are involved during recharging.


Answer:

A secondary cell after use can be recharged by passing current through it in the opposite direction so that it can be used again.

Recharging: During charging process, hydrogen ions moves to cathode and sulphate ions to anode and the following reactions take place
At cathode:
PbSO4 + H2 → Pb + H2SO4
At anode:
PbSO4 + SO4 + 2H2O → PbO2 + 2H2SO4
Thus, during charging active materials namely Pb cut the cathode and PbO2 at the anode are formed. Sulphuric acid is formed and water is iconsumed. Due to this, the specific gravity of sulphuric acid increases and emf of the cell goes up to 2.2 volt.

192 Views

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

At a particular spot of an object made of iron oxidation takes place and that spot behaves as an anode.
At anode: 2 Fe left parenthesis straight s right parenthesis rightwards arrow space 2 Fe to the power of 2 plus end exponent plus space 4 straight e to the power of minus
space space space space space space space space space space space space space space space space space space space space space space space space straight E to the power of 0 left parenthesis Fe to the power of 2 plus end exponent comma space Fe right parenthesis space equals space minus 0.44 straight V
Electrons released at anode spot moves through the metal and go to another spot on the metal and reduce oxygen in presence of H+ (which is believed to be available from H2CO3formed due to dissolution of carbondioxide from air into water. Hydrogen ion in water may also be available due to dissolution of other acidic oxides from the atmosphere). This spot behaves as a cathode with the reaction.

At a particular spot of an object made of iron oxidation takes place
The ferrous ions are further oxidized by atmospheric oxygen to ferric ions which come out as rust in the form of hydrated ferric oxide (Fe2Ox H2O).
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Suggest two materials other than hydrogen that can be used as fuels in fuel cells.


Answer:

Products are
(1)Methane (CH4)
(2)Methanol (CH3OH)
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