Question # 1

The oxidation state of an element is zero when

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It forms an oxide

It forms hydride

It is in free state

Only for noble gases

In the electrolysis of aqueous solution of sodium nitrate, the ions which are reduced at the cathode are

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H₃O⁺

Na⁺

OH^-

NO^3-

Caustic soda is obtained by electrolysis of conc. aqueous solution of NaCI in a cell called

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Daniell's cell

Nelson's cell

Down's cell

Voltaic cell

The reaction is galvanic cell is

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Spontaneous

Non-spontaneous

Acid-base

None of these

The substance having highest conductivity at room temperature among the following is

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0.1 N HCl

0.1 N NaCl

Graphite

Glass

Which one of the following reaction takes place spontaneously

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Which of the following statements is true about Galvanic cell

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Anode is negatively charged

Reduction occurs at anode

Cathode is positively charge

Reduction occurs at cathode

Standard reduction of Zn = -0.76 V and that of Ni is -0.25 V. On coupling them by a salt bridge which of these will act as anode

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Salt bridge will act as anode

Zn will act as anode

Ni will act as anode

None of these

If a salt bridge is removed between the two half cells, the voltage

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Drops to zero

Does not change

Increases gradually

Increases rapidly

During electrolysis, the reaction that takes place at cathode is :

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Reduction

Both (a) and (c)

Oxidation

No reaction occurs

Which statement is incorrect for balancing of redox reactions by ion-electron method

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The reaction is splitted into two half reactions

H₂O and H⁺ions are added for acidic or neutral reaction to balance O and H atoms

To balance H, HCi, is added

To balance O and H in the alkaline reaction OH^-added

The voltaic or galvanic cells which cannot be recharged are called

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Primary cells

Secondary cells

Infinite cells

Fuel cells

The reduction potential to copper electrode is +0.34 V and that of Zn electrode is -0.76 V. when these two are coupled the e.m.f. of the cell is

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-0.42 V

+0.42

-1.10 V

+1.10 V

K,Ca and Li metals may be arranged in decreasing order of their reduction potential as :

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Li, k, Ca

Ca, K, Li

Li, Ca, K

K, Ca, Li

In electronic watches or electronic calculators the tiny batteries used are

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Alkaline battery

NICAD battery

Fuel cell

Silver oxide battery

The oxidation number of free element is always taken to be

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0

1

2

-1

In a solution of CuSO₄how much time will be required to precipitate 2g copper by 0.5 ampere current?

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12157.48 sec

102 sec

510 sec

642 sec

A certain current liberate 0.5 g of hydrogen in 2 h. How many grams of copper can be liberated by the same time in a copper sulphate solution?

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12.7 gm

15.9 gm

31.8 gm

63.5 gm

96500 C of electricity liberates from CuSO₄solution

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63.5 g of Cu

31.75 g of Cu

96500 g of Cu

100 g of Cu

Reduction or oxidation potential of standard hydrogen electrode is :

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0.0 Volt

0.8Volt

1.0Volt

1.8Volt

For spontaneity of a cell, which is correct?

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ΔG = 0,ΔE = 0

ΔG = -ve ,ΔE = 0

ΔG = +ve ,ΔE = 0

ΔG = -ve

Ionization is the process in which ionic compounds when fused or dissolved in water split up into charged particles called :

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Atoms.

Electrons.

Protons .

Ions

Corrosion is basically a

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Altered reaction in presence of H₂O

Electrochemical phenomenon

Interaction

Union between two light metals and a heavy metal

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A strong reducing agent

A strong oxidising agent

Better oxidising agent than hydrogen

Less reducing agent than hydrogen

By using graphite electrode the electrolysis of aqueous solution of NaCI produces at anode

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H₂gas

Cl₂gas

NaOH

No metal

A dry alkaline cell has porous Zn anode and MnO₂as cathode the electrolyte used is

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Ca(OH)₂

NaOH

KOH

NH₄OH

In a Galvanic cell

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Chemical energy is converted into electricity

Chemical energy is converted into heat

Electrical energy is converted into heat

Electrical energy is converted into chemical energy

Coinage metals like Au, Pt, Ag and Cu are the least reactive metals and don't liberate H₂gas when treated with acids because

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These have very high positive values of reduction potentials

These have very high negative values of reduction potentials

Their ionization potentials are lowest

Their reduction potentials are close to SHE

The process of electrical coating of one metal on another to protect, decorate or to have greater resistance to corrosion is called

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Electroplating

Electrolysis

Conduction

Induction

Specific conductivity of a solution

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Increases with dilution

Decreases with dilution

Remains unchanged with dilution

Depends on mass of electrolyte

Zn does not displace Mg from MgSO₄solution because

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Zn is more electropositive than Mg

Zn is below Mg in electropositive series

Zn is above Mg in electrochemical series

Zn is trivalent Mg is divalent

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