Electrochemistry Test

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Electrochemistry Test - 29

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Question 1
1 / -0

How many faradays are required to reduce one mole of $$MnO^{\ominus}_4$$ to $$Mn^{2+}$$?

A
$$1$$

B
$$2$$

C
$$3$$

D
$$5$$

Solution

$$\displaystyle { MnO }_{ 4 }^{ - }+{ 8H }^{ + }+{ 5e }^{ - }\longrightarrow { Mn }^{ 2+ }+{ 5H }_{ 2 }O$$
$$1$$ mole of $$MnO_4^-$$ requires 5 mole of electrons = 5 faradays.
Question 2
1 / -0

$$CH_3COOH$$ is titrated with NaOH solution. Which of the following statement is true?

A
Conductance increases upto equivalence point, after which it decreases.

B
Conductance decreases upto equivalence point, after which it increases.

C
Conductance first increases (but not rapidly) upto equivalence point and then increases rapidly after equivalence point.

D
none

Solution

Weak Acid along with a Strong Base, example for acetic acid with NaOH:
Initially the conductance is low because of the feeble ionization of acetic acid. At the addition of base, there is reducing within conductance not only because of the replacement of $$H^+$$ through $$Na^+$$ but also suppresses the dissociation of acetic acid due to general ion acetate.
But extremely soon, the conductance increases on adding NaOH as NaOH neutralizes the un-dissociated $$CH_3COOH$$ to $$CH_3COONa$$ that is the strong electrolyte. This rise in conductance continues raise up to the equivalence point. The graph near the equivalence point is curved because the hydrolysis of salt $$CH_3COONa$$. Beyond the equivalence point, conductance increases more rapidly along with the addition of NaOH because of the highly conducting OH- ions display in the below figure.
Question 3
1 / -0

In electrolysis :

A
positive ions move toward the positive electrode and negative ions toward the negative electrode

B
positive ions move toward the negative electrode and negative ions toward the positive electrode

C
both ions move toward both the electrodes in equal amounts until they are balanced

D
none of the above

Solution

The process in which electrical current is passed through a substance to effect a chemical change. The chemical change is one in which the substance loses or gains an electron (oxidation or reduction) is called electrolysis.

The process is carried out in an electrolytic cell, an apparatus consisting of positive and negative electrodes held apart and dipped into a solution containing positively and negatively charged ions.

In this process, positive ions move toward the negative electrode and negative ions toward the positive electrode.
Question 4
1 / -0

The more negative the standard potential, the .............. is its ability to displace hydrogen from acids.

A
Greater

B
Lesser

C
Negetivity of the satndard potential has nothing to do with displacement of hydrogen

D
Depends on the acid

Solution

As we know,
More negative is the standard potential, higher is the probability to oxidise and because of that it has high ability to displace hydrogen from acids.
Question 5
1 / -0

Name the gas released at the cathode when acidulated water is electrolysed.

A
Hydrogen

B
Nitrogen

C
Oxygen

D
None of the above

Solution

Acidulated water is a mixture of cold water and small amount if vinegar ,lemon juice or lime juice. it's just used as a soak to prevent discoloration of some fruits and vegetables that darken quikly when their cut surfaces are exposed to air. During electrolysis of acidulated water, hydrogen gas $$(H_2)$$ is liberated at cathode.
Question 6
1 / -0

Rusting of iron involves:

A
oxidation

B
reduction

C
decomposition

D
displacement

Solution

Rusting of iron involves oxidation.
Question 7
1 / -0

A compound which liberates reddish brown gas around the anode during electrolysis in its molten state is -

A
Sodium chloride

B
Copper (II) oxide

C
Copper (II) sulphate

D
Lead (II) bromide

Solution

We know that Bromine gas is reddish brown in colour and which can only liberates during electrolysis of Lead (II) bromide $$(PbBr_2)$$
During electrolysis of Lead (II) bromide , Positive lead ions (cations) move to the cathode and gain electrons to become lead metal and . negative bromide ions (anions) move to the anode and loose an electron to make chlorine atoms. Two bromine atoms then combine and the diatomic bromine gas $$(Br_2)$$ is released at the anode.
Therefore, D is correct option.
Question 8
1 / -0

Electrons are getting added to an element Y. Which electrode will Y migrate to during electrolysis?

A
Anode

B
Cathode

C
will not migrate

D
will move randomly

Solution

On adding electrons to $$Y$$, it will get negatively charged and hence will migrate to positive electrode that is $$anode$$.

Answer_(A)
Question 9
1 / -0

Aluminium is more reactive than iron. But aluminium is less easily corroded than iron because:

A
aluminium is a noble metal

B
oxygen forms a protective oxide layer on aluminium surface

C
iron unergoes reaction easily with water

D
iron forms both mono and divalent ions

Solution

Corrosion resistance of aluminium is due to formation of thin layer of aluminium oxide that forms when metal is exposed to air and prevents further oxidation. It is called as protective passivation.
Question 10
1 / -0

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)

A
0.50A

B
1A

C
Zero

D
2.5A

Solution

ECE of chromium=$$0.00018g/C$$=mass of chromium deposited per coulomb of charge.

Hence charge needed for depositing $$0.972g$$ of chromium$$=q=\dfrac{0.972}{0.00018}=5400C$$

Time$$=t=3hr=3\times 3600s=10800s$$

Current$$=I=\dfrac{q}{t}=\dfrac{5400}{10800}$$

$$\implies I=0.5A$$

Answer-(A)

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Electrochemistry Test - 29

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Electrochemistry Test - 29

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Question 1

$$1$$

$$2$$

$$3$$

$$5$$

Solution

Question 2

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

Solution

Question 3

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

Solution

Question 4

Greater

Lesser

Negetivity of the satndard potential has nothing to do with displacement of hydrogen

Depends on the acid

Solution

Question 5

Hydrogen

Nitrogen

Oxygen

None of the above

Solution

Question 6

oxidation

reduction

decomposition

displacement

Solution

Question 7

Sodium chloride

Copper (II) oxide

Copper (II) sulphate

Lead (II) bromide

Solution

Question 8

Anode

Cathode

will not migrate

will move randomly

Solution

Question 9

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

Solution

Question 10

0.50A

1A

Zero

2.5A

Solution

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