CBSE Questions for Class 12 Engineering Chemistry Electrochemistry Quiz 7 - MCQExams.com

In the rusting of iron, iron has been:
  • oxidised
  • reduced
  • vaporised
  • decomposed
Identify the false statement among the following:
  • Oxidation takes place at positive electrode in electrolytic cell whereas at negative electrode in voltaic cell
  • Deposition of metals takes place in both electrolytic cell and galvanic cell
  • Direction of flow of current is from cathode to anode in electrolytic cell
  • Both $$A$$ and $$B$$
During electrolysis, cations move towards the positive terminal.
  • True
  • False
Given the standard potential of the following at $$25^{\circ}C$$. $$MnO_{2}\, \rightarrow\, Mn^{3+}$$; $$E^{\ominus}\, =\, 0.95\, V$$ 
$$Mn^{3+}\, \rightarrow\, Mn^{2+}$$; $$E^{\ominus}\, =\, 1.51\, V$$
The standard potential of $$MnO_{2}\, \rightarrow\, Mn^{2+}$$ is :
  • 1.23 V
  • 0.2 V
  • 0.02 V
  • None of these
The half cell involving the reaction $$Cr_2O_7^{2-} (aq) + 14 H^+ (aq) + 6e   \rightarrow 2Cr^{3+} (aq) + 7H_2O$$ can be represented as :
  • $$Pt, H^+ (aq), Cr_2O_7^{2-} (aq)$$
  • $$Pt, H^+ ,Cr^{3+} (aq)$$
  • $$Pt, H_2, Cr_2O_7^{2-} (aq), Cr^{3+} (aq)$$
  • $$Pt, H^+, Cr_2O_7^{2-} (aq), Cr^{3+} (aq)$$
Rusting of iron is catalysed by :
  • H$$^+$$ ions
  • dissolved $$CO_2$$ in water
  • O$$_2$$
  • impurities present
In the atmosphere of industrial smog, copper corrodes to form:
  • basic copper carbonate and sulphate
  • copper oxide
  • copper sulphide
  • copper nitrate
Which of the following statements is incorrect?
  • Tarnishing of silver is due to the formation of $$Ag_2S$$ and $$Ag_2O$$
  • Green deposit on Cu terminal of battery are due to the formation of $$CuCO_3$$
  • Brown deposits on Fe is due to formation of rust
  • White deposits on Al pan is due to the formation of $$Al_2O_3$$
The tarnishing of silver ornaments in the atmosphere is due to the formation of:
  • $$Ag_2O, Ag_2S$$
  • $$AgNO_3, Ag_2S$$
  • $$AgOH, Ag_2CO_3$$
  • $$Ag$$
State True or False.
Corrosion of motor cars is the major problem in the winter, when salt is spread on road to melt ice and snow.
  • True
  • False
Electrolysis is the passage of electricity through a liquid or a solution accompanied by a chemical change.
  • True
  • False
State True or False.

Corrosion of iron is a redox process.
  • True
  • False
In moist air, iron is oxidized to give:
  • iron$$[II]$$ oxide
  • iron$$[III]$$ oxide
  • iron$$[II]$$ hydroxide
  • iron$$[II]$$ sulphide
Corrosion can not be prevented by which of the following method?
  • Galvanisation
  • Create a barrier between the object being corroded and oxygen
  • Painting
  • Exposing it to sunlight
Assertion: Cations migrate at cathode during electrolysis.
Reason: Reduction always occurs at cathode.
  • Both Assertion and Reason are true and Reason is the correct explanation of Assertion
  • Both Assertion and Reason are true but Reason is not the correct explanation of Assertion
  • Assertion is true but Reason is false
  • Assertion is false but Reason is true
  • Both Assertion and Reason are false
If edible oil is allowed to stand for a long time in an iron or tin container, the oil becomes rancid.
  • True
  • False
Which metals does not corrode easily?
  • Gold
  • Iron
  • Aluminium
  • Zinc
The resistance of solution decreases with increase in temperature.
  • True
  • False
An electrochemical cell stops working after some time because:
  • electrode potential of both the electrodes becomes zero
  • electrode potential of both the electrodes become equal.
  • one of the electrode is eaten away.
  • the reaction starts proceeding in opposite direction
When iron is rusted, it is :
  • reduced
  • oxidised
  • evaporated
  • decomposed

Given standard $$E^{\ominus}$$:

$$Fe^{3+}\, +\, 3e^-\, \rightarrow\, Fe$$; $$E^{\ominus}\, =\, -\, 0.036\, V$$ 

$$Fe^{2+}\, +\, 2e^-\, \rightarrow\, Fe$$; $$E^{\ominus}\, =\, -\, 0.440\, V$$ 

The $$E^{\ominus}$$ of $$Fe^{3+}\, +\, e^-\, \rightarrow\, Fe^{2+}$$ is:
  • $$0.476 V$$
  • $$0.404 V$$
  • $$0.604 V$$
  • $$0.772 V$$
Total charge required to convert three moles of $$Mn_3O_4$$ to $$MnO_4^{-}$$ in alkaline medium will be:
  • $$10 F$$
  • $$20F$$
  • $$30 F$$
  • $$40 F$$

The rusting of iron takes place as follows : $$2H^{+} +2e + \dfrac{1}{2} O_{2} \rightarrow H_2O(l) ; E^{o}= + 1.23 V$$

$$Fe^{2+} + 2e\rightarrow Fe(s); E^{o} = - 0.44 V$$

$$\Delta G^{o}$$ for the net process is:
  • $$-322$$  $$kJ\ mol^{-1}$$
  • $$-161$$  $$kJ\ mol^{-1}$$
  • $$-152$$  $$kJ\ mol^{-1}$$
  • $$-76$$  $$kJ\ mol^{-1}$$
When the electric current is passed through a cell having an electrolyte, the positive ions move towards cathode and negative ions towards the anode. If the cathode is pulled out of the solution :-
  • the positive and negative ions will move towards anode
  • the positive ions will start moving towards the anode while negative ions will stop moving
  • the negative ions will continue to move towards anode while positive ions will stop moving
  • the positive and negative ions will start moving randomly
The presence of electrolytes ................ the rate of corrosion. 
  • increases
  • decreases
  • sharply decreases
  • does not effect
20 mL of KOH solution was titrated with 0.20 M $$H_2SO_4$$ solution in a conductivity cell. The data obtained were plotted to give the graph shown below.
The concentration of the KOH solution was :

259483_7c4e7de87daa4622984cce0d24f44051.png
  • $$0.30\, mol\, L^{-1}$$
  • $$0.15\, mol\, L^{-1}$$
  • $$0.12\, mol\, L^{-1}$$
  • $$0.075\, mol\, L^{-1}$$
_____ refers to amount of electricity while _____ refers to rate at which it flows.
  • Ampere, coloumb
  • Coloumb, ampere
  • Faraday, coloumb
  • Coloumb, faraday
How many faradays are required to reduce one mole of $$MnO^{\ominus}_4$$ to $$Mn^{2+}$$?
  • $$1$$
  • $$2$$
  • $$3$$
  • $$5$$
The more negative the standard potential, the .............. is its ability to displace hydrogen from acids.  
  • Greater
  • Lesser
  • Negetivity of the satndard potential has nothing to do with displacement of hydrogen
  • Depends on the acid
The process of breaking down of a compound by passing electric current through it is called:
  • hydrolysis
  • photosynthesis
  • electrolysis
  • distillation
Corrosion of metals can be prevented when contact between metal and .......... is cut off.
  • Nitrogen
  • Hydrogen
  • Oxygen
  • Carbon
Corrosion of metals can be prevented when contact between metal and ________ is cut off.
  • nitrogen
  • hydrogen
  • oxygen
  • carbon
In an electrochemical cell that function as a voltaic cell:
  • electrons move from the cathode to the anode
  • electrons move through a salt-bridge
  • electrons can move either from the cathode to the anode or from the anode to the cathode
  • reduction occurs at the cathode
The amount of ion discharged during electrolysis is not directly proportional to :
  • resistance
  • time
  • current
  • chemical equivalent of ion
$$CH_3COOH$$ is titrated with NaOH solution. Which of the following statement is true?
  • Conductance increases upto equivalence point, after which it decreases.
  • Conductance decreases upto equivalence point, after which it increases.
  • Conductance first increases (but not rapidly) upto equivalence point and then increases rapidly after equivalence point.
  • none
In electrolysis :
  • positive ions move toward the positive electrode and negative ions toward the negative electrode
  • positive ions move toward the negative electrode and negative ions toward the positive electrode
  • both ions move toward both the electrodes in equal amounts until they are balanced
  • none of the above
On electrolysis, water splits into:
  • positively charged hydrogen ions and negatively charged hydroxide ions
  • negatively charged hydrogen ions and positively charged oxygen ions
  • hydrogen and oxygen atoms having positive and negative charges respectively
  • hydrogen and oxygen atoms having negative and positive charges respectively
Name the gas released at the cathode when acidulated water is electrolysed.
  • Hydrogen
  • Nitrogen
  • Oxygen 
  • None of the above 
Rusting of iron involves:
  • oxidation
  • reduction
  • decomposition
  • displacement
A compound which liberates reddish brown gas around the anode during electrolysis in its molten state is -
  • Sodium chloride
  • Copper (II) oxide
  • Copper (II) sulphate
  • Lead (II) bromide
Electrons are getting added to an element Y. Which electrode will Y migrate to during electrolysis?
  • Anode
  • Cathode
  • will not migrate
  • will move randomly
Which of the following methods is suitable for preventing an iron vessel from rusting ?
  • Applying grease
  • Applying paint
  • Applying a coat of zinc
  • All of the above.
Which of the following statements is true ?
  • Electrolysis is one of the applications of chemical effects of current
  • A metal wire shows chemical effect when a current is passed through it
  • Like charges attract each other
  • Charge flows only through negative charge carriers
Aluminium is more reactive than iron. But aluminium is less easily corroded than iron because:
  • aluminium is a noble metal
  • oxygen forms a protective oxide layer on aluminium surface
  • iron unergoes reaction easily with water
  • iron forms both mono and divalent ions
What is the electric current required to deposit 0.972 g of chromium in three hours?
(E.C.E. of chromium is 0.00018 g/c)
  • 0.50A
  • 1A
  • Zero
  • 2.5A
How much electricity must pass through acidulated water to release $$22, 400\, cm^3$$ of hydrogen at N.T.P.?
  • 96500 C
  • 193000 C
  • 22.4 C
  • 95.5 C
Rusting of iron is a chemical reaction. The reaction can be termed as:
  • combination reaction
  • addition reaction
  • both (A) and (B)
  • decomposition
Select the correct statements about the electrolysis_________.
  • Electric current is used to drive a non spontaneous reaction
  • $$\displaystyle \Delta G$$ is positive for chemical process during electrolysis
  • Cations and anions move towards the anode in the anode and cathode respectively
  • Over voltage is generally associated with anode in the electrolysis of $$\displaystyle NaCl(aq)$$
A solution of sodium chloride discharges $$6.1 \times 10^{16} Na^+$$ ions and $$4.6 \times 10^{16} Cl^-$$ ions in 10 seconds. Find the current passing through the solution.
  • 1.7 mA
  • 1.8 mA
  • 1.9 mA
  • 1.6 mA
A voltaic cell converts:
  • electrical energy into chemical energy
  • chemical energy into electrical energy
  • light energy into electrical energy
  • mechanical energy into electrical energy
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