Electrochemistry Flashcards
(21 cards)
conductivity of electrolytic (ionic)
solutions depends on:
6 factors
(i) the nature of the electrolyte added
(ii) size of the ions produced
(iii) the nature of the solvent and its viscosity
(iv) concentration of the electrolyte
(v) temperature (it increases with the increase of temperature).
(vi) solvation of ions
If reduction potential of metal ion is greater then O2/H2O couple, the ion is………
stable in water.
Coulometer (a standard electrolytic
cell) is used for…………
for determining the quantity of electricity passed from the amount
of metal (generally silver or copper) deposited or consumed.
Statement 1: If the electrode is
inert (platinum or gold) it does not participate in the chemical
reaction and acts only as source or sink for electrons.
Statement 2: Some of the electrochemical processes
although feasible, are so slow kinetically that at lower voltages these do not seem to take place and extra potential (called overpotential) be applied, which makes such process more difficult to occur.
Both statements are true
Statement 1: Nowadays a number of ceramic materials and mixed oxides are also known to show
superconductivity at temperatures as high as 150 K.
Statement 2: Very pure water has small amounts of
hydrogen and hydroxyl ions (~10–7M) which lend it very low conductivity
3.5 × 10–5 S m–1
Both statements are correct
Conductivity of electrolytic (ionic)
solutions depends on: 5 factors
(i) the nature of the electrolyte added
(ii) size of the ions produced and their solvation
(iii) the nature of the solvent and its viscosity
(iv) concentration of the electrolyte
(v) temperature (it increases with the increase of temperature)
Measuring the resistance
of an ionic solution we face two problems.
Firstly, passing direct current
(DC) changes the composition of the solution.
Secondly, a solution cannot
be connected to the bridge like a metallic wire or other solid conductor.
Assertion Difficulty in measuring resistance of electrolyte solutions can be solved.
Reason: The first difficulty is resolved by using an alternating current (AC) source
of power. The second problem is solved by using a specially designed
vessel called conductivity cell.
Both assertion and reason are correct and R is correct explanation of A
Discharge potential may be defined as…….
Minimum potential applied in order to bring about electrolysis
Assertion: NaCl, CaCl2, MgSO4 are known as 1-1, 2-1 and 2-2
electrolytes respectively.
Reason: The value of the constant ‘A’ for a given solvent and
temperature depends on the type of electrolyte i.e., the charges on the
cation and anion produced on the dissociation of the electrolyte in the
solution.
Both are correct
A secondary cell ………… has longer life span than lead storage battery but is expensive to manufacture
Nickel cadmium battery
A rechargeable………… cell in a jelly roll arrangement and separated by a layer soaked in moist…………
nickel-cadmium
sodium or potassium hydroxide.
Reaction in Nickel cadmium battery
Cd (s) + 2Ni(OH), (s) → CdO (s) + 2Ni(OH), (s) + H,0 (l)
The rusting of iron, tarnishing of silver, development of green coating on copper and bronze are some of the examples of………
corrosion
At a particular spot of an object made of iron, oxidation takes place and that spot behaves as……….. and the reaction is….
Anode:
2 Fe (s) → 2 Fe2+ + 4 e–
Statement 1: Electrons released at anodic spot move through the metal and go to another spot which behaves as cathode on the metal and reduce oxygen in the presence of H+
Statement 2: These H+ are believed to be available from H2CO3 formed due to dissolution of carbon dioxide from air into water or dissolution of other acidic oxides from atmosphere
Both are correct
O2(g) + 4 H+(aq) + 4 e– → 2 H2O (l)
The ferrous ions are further oxidised by atmospheric oxygen to ferric ions which come out as rust in the form of hydrated ferric oxide…………and with further production of……… ions.
Fe2O3. x H2O
hydrogen
Statement 1: One of the simplest methods of preventing corrosion is to prevent the surface of the metallic object to come in contact with atmosphere
Statement 2: This can be done by covering the surface with paint or by some chemicals (e.g. bisphenol)
Both are correct
One more simple method is to cover the surface by other metals…../….
Sn, Zn
An electrochemical method is to provide a sacrificial electrode of another metal like ……./…… which corrodes itself but saves the object.
Mg
Zn
Suggest two materials other than hydrogen that can be used as fuels in fuel cells.
Methanol and methane
