# Electrochemistry Test 5

Total Questions:50 Total Time: 75 Min

Remaining:

## Questions 1 of 50

Question:For cell reaction, $$Zn + C{u^{2 + }} \to Z{n^{2 + }} + Cu,$$ cell representation is cell cell

Zn | Zn2+||Cu2+|Cu

Cu | Cu2+ ||Zn2+| Zn

Cu | Zn2+ || Zn | Cu2+

Cu2+ | Zn || Zn2+ | Cu

## Questions 2 of 50

Question:Which one is not called a anode reaction from the following

$$C{l^ - }\, \to \,\frac{1}{2}C{l_2} + {e^ - }$$

$$Cu\, \to \,C{u^{ + + }} + 2{e^ - }$$

$$H{g^ + }\, \to \,H{g^{ + + }} + {e^ - }$$

$$Z{n^{2 + }} + 2{e^ - }\, \to \,Zn$$

## Questions 3 of 50

Question:In the reaction$$Cu(s) + 2A{g^ + }(aq) \to C{u^{2 + }}(aq) + 2Ag(s)$$ The reduction half-cell reaction is

$$Cu + 2{e^ - } \to C{u^{2 - }}$$

$$Cu - 2{e^ - } \to C{u^{2 + }}$$

$$A{g^ + } + {e^ - } \to Ag$$

$$Ag - {e^ - } \to A{g^ + }$$

## Questions 4 of 50

Question:Which of the following statements about galvanic cell is incorrect

Anode is positive

Oxidation occurs at the electrode with lower reduction potential

Cathode is positive

Reduction occurs at cathode

## Questions 5 of 50

Question:If a strip of $$Cu$$ metal is placed in a solution of ferrous sulphate

Copper will precipitate out

Iron will precipitate out

Copper will dissolve

No reaction will take place

## Questions 6 of 50

Question:Which of the following is not used to construct salt bridge

$$C{H_3}COOK$$

$$KCl$$

$$N{H_4}N{O_3}$$

$$KN{O_3}$$

## Questions 7 of 50

Question:The reference electrode is made by using

$$ZnC{l_2}$$

$$CuS{O_4}$$

$$HgC{l_2}$$

$$H{g_2}C{l_2}$$

## Questions 8 of 50

Question:When electric current is supplied through an ionic hydride of fused state, then

Hydrogen is obtained at anode

Hydrogen is obtained at cathode

No change

Hydride ion moves towards cathode hydride ion present in solution

## Questions 9 of 50

Question:Which one of the following statements is correct

The oxidation number of oxygen in $$K{O_2}$$ is zero

The specific conductance of an electrolyte solution decreases with increase in dilution

$$S{n^{2 + }}$$ oxidises $$F{e^{3 + }}$$

$$Zn/ZnS{O_4}$$ is a reference electrode

## Questions 10 of 50

Question:In infinite dilutions, the equivalent conductances of $$B{a^{2 + }}$$ and $$C{l^ - }$$ are 127 and 76 $$oh{m^{ - 1}}c{m^{ - 1}}$$ $$eqv{t^{ - 1}}$$. The equivalent conductivity of $$BaC{l_2}$$at indefinite dilution is

101.5

139.5

203.5

279.5

## Questions 11 of 50

Question:The electrolytic conductance is a direct measure of

Resistance

Potential

Concentration

Dissociation

## Questions 12 of 50

Question:Conductivity of a strong electrolyte

Increases on dilution

Does not change considerably on dilution

Decreases on dilution

Depends on density

## Questions 13 of 50

Question:Which of the following statements is not applicable to electrolytic conductors

New products show up at the electrodes

Ions are responsible for carrying the current

Show a positive temperature coefficient for conductance

A single stream of electrons flows from cathode to anode

## Questions 14 of 50

Question:The hydrogen electrode is dipped in a solution of $$pH = 3$$ at $${25^o}C$$. The potential of the cell would be (the value of $$2.303RT/F$$ is 0.059 V)

0.177 V

0.177 V

0.087 V

0.059 V

## Questions 15 of 50

Question:The standard electrode potentials of $$Z{n^{2 + }}/Zn$$ and $$A{g^ + }/Ag$$ are $$- \,0.763\,V$$ and $$+ \,0.799\,V$$ respectively. The standard potential of the cell is

1.56 V

0.036 V

1.562 V

0.799 V

## Questions 16 of 50

Question:The standard reduction potentials at $$298\,K$$for the following half reactions are given against each $$Z{n^{2 + }}(aq.) + 2e$$?$$Zn(s)$$; – 0.762 $$C{r^{3 + }}(aq) + 3e$$?$$Cr(s)$$; – 0.740 $$2{H^ + }(aq) + 2e$$?$${H_2}(g)$$; 0.00 $$F{e^{3 + }}(aq) + e$$?$$F{e^{2 + }}(aq)$$; 0.770 . Which is the strongest reducing agent

$$Zn(s)$$

$$Cr(s)$$

$${H_2}(g)$$

$$F{e^{2 + }}(aq)$$

## Questions 17 of 50

Question:Which one of the following metals cannot evolve $${H_2}$$from acids or $${H_2}O$$ or from its compounds

$$Hg$$

$$Al$$

$$Pb$$

$$Fe$$

## Questions 18 of 50

Question:Which one of the following reaction is not possible

$$Fe + {H_2}S{O_4}\, \to \,\,FeS{O_4} + {H_2}$$

$$Cu + 2AgN{O_3}\, \to \,Cu\,{(N{O_3})_2} + 2Ag$$

$$2KBr + {I_2}\, \to \,\,2KI + B{r_2}$$

$$CuO + {H_2}\, \to \,\,Cu + {H_2}O$$

## Questions 19 of 50

Question:When a rod of metal $$A$$ is dipped in an aqueous solution of metal $$B$$(concentration of $${B^{2 + }}$$ion being 1M) at $${25^o}C$$, the standard electrode potentials are $${A^{2 + }}/A$$=–0.76 volts, $${B^{2 + }}$$/B = + 0.34 volts

$$A$$ will gradually dissolve

$$B$$ will deposit on $$A$$

No reaction will occur

Water will decompose into $${H_2}$$ and $${O_2}$$

## Questions 20 of 50

Question:The standard reduction potential for $$F{e^{2 + }}/Fe$$ and $$S{n^{2 + }}/Sn$$ electrodes are $$- 0.44$$ and $$- 0.14$$ volt respectively. For the given cell reaction $$F{e^{2 + }} + Sn\, \to Fe + S{n^{2 + }}$$, the standard EMF is

+ 0.30 V

0.58 V

+ 0.58 V

0.30V

## Questions 21 of 50

Question:Electrode potential of $$Z{n^{2 + }}/Zn$$ is $$- 0.76\,V$$ and that of $$C{u^{2 + }}/Cu$$ is $$+ 0.34V$$. The EMF of the cell constructed between these two electrodes is

1.10 V

0.42 V

1.1V

0.42 V

## Questions 22 of 50

Question:EMF of a cell whose half cells are given below is $$M{g^{2 + }} + 2{e^ - } \to Mg(s);\,\,E = - 2.37\,V$$ , $$C{u^{2 + }} + 2{e^ - } \to Cu(s);\,\,\,E = + 0.33\,V$$

2.03 V

1.36 V

2.7 V

2.03 V

## Questions 23 of 50

Question:(i) Copper metal dissolves in 1M silver nitrate solution and crystals of silver metal get deposited. (ii) Silver metal does not react with 1 M zinc nitrate solution (iii) Zinc metal dissolves in 1M copper sulphate solution and copper metal gets deposited. Hence the order of decreasing strength of the three metals as reducing agents will be

$$Cu\, > \,Ag\, > \,Zn$$

$$Ag\, > \,Cu\, > \,Zn$$

$$Zn\, > \,Cu\, > \,Ag$$

$$Cu\, > \,Zn\, > \,Ag$$

## Questions 24 of 50

Question:Standard electrode potentials of $$Zn$$ and $$Fe$$ are known to be (i) $$- 0.76\,V$$ and (ii) $$- 0.44\,V$$ respectively. How does it explain that galvanization prevents rusting of iron while zinc slowly dissolves away

Since (i) is less than (ii), zinc becomes the cathode and iron the anode

Since (i) is less than (ii), zinc becomes the anode and iron the cathode

Since (i) is more than (ii), zinc becomes the anode and iron the cathode

Since (i) is more than (ii), zinc becomes the cathode and iron the anode

## Questions 25 of 50

Question:The e.m.f. of the cell in which the following reaction $$Zn(s) + N{i^{2 + }}(a = 1.0)$$? $$Z{n^{2 + }}(a = 10) + Ni(s)$$ occurs, is found to be $$0.5105\,V$$ at $$298K$$. The standard e.m.f. of the cell is

0.54

0.4810 V

0.5696 V

0.5105 V

## Questions 26 of 50

Question:For the redox reaction $$Zn(s) + C{u^{2 + }}(0.1M) \to Z{n^{2 + }}(1M) + Cu(s)$$ taking place in a cell, $$E_{cell}^o$$ is 1.10 volt. $${E_{cell}}$$ for the cell will be $$\left( {2.303\frac{{RT}}{F} = 0.0591} \right)$$

2.14 volt

1.80 volt

1.07 volt

0.82 volt

## Questions 27 of 50

Question:Which will increase the voltage of the cell $$S{n_{(s)}} + 2A{g^ + }_{(aq)} \to S{n^{2 + }}_{(aq)} + 2A{g_{(s)}}$$

Increase in the concentration of $$A{g^ + }$$ions

Increase in the concentration of $$S{n^{2 + }}$$ions

Increase in size of the silver rod

None of these

## Questions 28 of 50

Question:The mass of the proton is 1840 times that of electron, its potential difference is V. The kinetic energy of proton is

1840 KeV

1 KeV

$$\frac{1}{{1840}}$$ KeV

920 KeV

## Questions 29 of 50

Question:In the experiment set up for the measurement of EMF of a half cell using a reference electrode and a salt bridge, when the salt bridge is removed, the voltage

Does not change

Decreases to half the value

Increase to maximum

Drops to zero

## Questions 30 of 50

Question:Electrode potentials of five elements $$A,\,B,\,C,\,D$$ and $$E$$ are respectively – 1.36 , – 0.32, 0, – 1.26 and –0.42. The reactivity order of these elements are in the order of

A, D, E, B and C

C, B, E, D and A

B, D, E, A and C

C, A, E, D and B

## Questions 31 of 50

Question:For the cell reaction, $$2C{e^{4 + }} + Co \to 2C{e^{3 + }} + C{o^{2 + }}$$ $$E{^\circ _{cell}}$$is 1.89 V. If $$E{^\circ _{C{e^{4 + }}/C{e^{3 + }}}}$$

1.64 V

+ 1.64 V

2.08 V

+ 2.17 V

## Questions 32 of 50

Question:If the $$\Delta G$$ of a cell reaction $$AgCl + {e^ - } \to Ag + C{l^ - }$$ is $$- 21.20\;KJ$$; the standard e.m.f., of cell is

0.229 V

0.220 V

0.220 V

0.110 V

## Questions 33 of 50

Question:For the feasibility of a redox reaction in a cell, the e.m.f. should be

Positive

Fixed

Zero

Negative

## Questions 34 of 50

Question:Which of the following will not conduct electricity in aqueous solution

Copper sulphate

Sugar

Common salt

None of these

## Questions 35 of 50

Question:A solution of sodium sulphate in water is electrolysed using inert electrodes. The products at the cathode and anode are respectively

$${H_2},\,\,\,{O_2}$$

$${O_2},\,\,{H_2}$$

$${O_2},\,\,Na$$

$${O_2},\,\,S{O_2}$$

## Questions 36 of 50

Question:On electrolysing a solution of dilute $${H_2}S{O_4}$$ between platinum electrodes, the gas evolved at the anode is

$$S{O_2}$$

$$I{F_5}$$

$${O_2}$$

$${H_2}$$

## Questions 37 of 50

Question:Which of the following is non-electrolytes

$$NaCl$$

$$CaC{l_2}$$

$${C_{12}}{H_{22}}{O_{11}}$$

$$C{H_3}COOH$$

## Questions 38 of 50

Question:When a molten ionic hydride is electrolysed

Hydrogen is liberated at the cathode

Hydrogen is liberated at the anode

There is no reaction

$${H^ - }$$ ions produced migrate to the cathode

## Questions 39 of 50

Question:A certain current liberated 0.504 gm of hydrogen in 2 hours. How many grams of copper can be liberated by the same current flowing for the same time in a copper sulphate solution

12.7 gm

15.9 gm

31.8 gm

63.5 gm

## Questions 40 of 50

Question:What weight of copper will be deposited by passing 2 Faradays of electricity through a cupric salt (Atomic weight of Cu = 63.5)

2.0 gm

3.175 gm

63.5 gm

127.0 gm

## Questions 41 of 50

Question:In electrolysis of a fused salt, the weight of the deposit on an electrode will not depend on

Temperature of the bath

Current intensity

Electrochemical equivalent of ions

Time for electrolysis

## Questions 42 of 50

Question:Faraday's laws of electrolysis will fail when

Temperature is increased

Inert electrodes are used

A mixture of electrolytes is used

In none of these cases

## Questions 43 of 50

Question:How much chlorine will be liberated on passing one ampere current for 30 minutes through NaCl solution

0.66 mole

0.33 mole

0.66 gm

0.33 gm

## Questions 44 of 50

Question:The number of electrons involved in redox reactions when a Faraday of electricity is passed through an electrolyte in solution is

$$6 \times {10^{23}}$$

$$6 \times {10^{ - 23}}$$

96500

$$8 \times {10^{19}}$$

## Questions 45 of 50

Question:Three faradays of electricity are passed through molten $$A{l_2}{O_3}$$, aqueous solution of $$CuS{O_4}$$ and molten $$NaCl$$ taken in different electrolytic cells. The amount of $$Al,\,Cu$$ and $$Na$$ deposited at the cathodes will be in the ratio of

1 mole : 2 mole : 3 mole

3 mole : 2 mole : 1mole

1 mole : 1.5 mole : 3 mole

1.5 mole : 2 mole : 3 mole

## Questions 46 of 50

Question:An electrolytic cell contains a solution of $$A{g_2}S{O_4}$$ and have platinum electrodes. A current is passed until 1.6 gm of $${O_2}$$ has been liberated at anode. The amount of silver deposited at cathode would be

107.88 gm

1.6 gm

0.8 gm

21.60 gm

## Questions 47 of 50

Question:In order to separate oxygen from one mole of $${H_2}O$$ the required quantity of coulomb would be

$$1.93 \times {10^5}$$

$$9.6 \times {10^4}$$

1.8

3.2

## Questions 48 of 50

Question:A current of 0.25A is passed through $$CuS{O_4}$$ solution placed in voltameter for 45 minutes. The amount of Cu deposited on cathode is (At weight of $$Cu = 63.6$$)

0.20 g

0.22 g

0.25 g

0.30 g

## Questions 49 of 50

Question:The number of coulombs required to reduce 12.3 g of nitrobenzene to aniline

115800 C

5790 C

28950 C

57900 C

## Questions 50 of 50

Question:During the process of electrolytic refining of copper, some metals present as impurity settle as 'anode mud'. These are