Electrochemistry Test

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Electrochemistry Test - 35

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Question 1
1 / -0

What is corrosion?

A
When metal is gradually destroyed through chemical reactions

B
When metal is created through chemical reactions

C
When a redox reaction takes place

D
When a metal is destroyed after exposure to a gas

E
When a solid is destroyed through chemical reactions

Solution

Corrosion occurs when a redox reaction takes place.
Corrosion is a natural process, which converts a refined metal to a more chemically-stable form, such as its oxide, hydroxide, or sulfide. It is the gradual destruction of materials by chemical and/or electrochemical reaction with their environment.
It also gradually destroys the element through chemical reactions

Hence, the correct options are $$A$$ and $$C$$
Question 2
1 / -0

What is the voltage of the voltaic cell $$Zn|Zn^{2+}||Cu^{2+}|Cu$$ at $$298\ K$$ if $$[Zn^{2+}] = 0.2\ M$$ and $$[Cu^{2+}] = 4.0\ M$$?
$$Cu^{2+} + 2e^{-}\rightarrow Cu\ E^{\circ} = +0.34V$$
$$Zn^{2+} + 2e^{-}\rightarrow Zn\ E^{\circ} = -0.76\ V$$
[Note: $$E = E^{\circ} - (0.0591/n)(\log Q)$$

A
$$+1.10\ V$$

B
$$-1.10\ V$$

C
$$+1.07\ V$$

D
$$+1.14\ V$$

E
$$-1.07\ V$$

Solution

The representation of the voltaic cell shows that $$Zn$$ is oxidised to $$Zn^{2+}$$, whereas, $$Cu^{2+}$$ is reduced to $$Cu$$.
These two phenomenons can be written by two equations-
$$Cu^{2+}$$$$+$$$$2e^-$$$$\rightarrow$$$$Cu$$..... $$E^o$$$$=$$ $$+0.34V$$, (since $$Cu^{2+}$$ is reduced)..... $$eq(1)$$
and
$$Zn^{2+}$$$$+$$$$2e^-$$$$\rightarrow$$$$Zn$$..... $$E^o$$$$=$$ $$-0.76V$$
But the voltaic cell represents that $$Zn$$ is oxidised to $$Zn^{2+}$$, hence the equation must be written as-
$$Zn$$$$\rightarrow$$$$Zn^{2+}$$$$+$$$$2e^-$$..... $$E^o$$$$=$$ $$+0.76V$$, (since $$Zn$$ is oxidised)......$$eq(2)$$
Adding $$eq(1)$$ and $$eq(2)$$, we get,
$$Cu^{2+}$$$$+$$$$Zn$$$$+$$$$2e^-$$$$\rightarrow$$$$Cu$$$$+$$$$Zn^{2+}$$$$+$$$$2e^-$$...... $$E^o$$$$=$$$$0.34+0.76$$$$=$$$$1.10V$$
Or, $$Cu^{2+}$$$$+$$$$Zn$$$$\rightarrow$$$$Cu$$$$+$$$$Zn^{2+}$$..... $$E^o$$$$=$$ $$+1.10V$$
We also know the formula-
$$E$$ $$=$$ $$E^o$$ $$-$$ $$\dfrac{0.0591}{n}$$$$(logQ)$$
Q can be written as $$Q$$$$=$$$$\dfrac{[Zn^{2+}]}{[Cu^{2+}]}$$ and $$n$$ is the number of electrons, that is $$2$$
Putting the values of all the known quantities in the given equation we get,
$$E$$ $$=$$ $$1.10$$ $$-$$ $$\dfrac{0.0591}{2}$$$$log$$$$\dfrac{[0.2]}{[4.0]}$$
Thus, $$E$$$$=$$$$1.10-(-0.038)$$
$$E$$$$=$$$$1.138V$$, that is $$1.14V$$
Option D is the correct answer.
Question 3
1 / -0

In the diagram above, what is the half reaction that occurs at the cathode?

A
$$Al \rightarrow Al^{3+} + 3e^-$$

B
$$Ni^{2+} + 2e^- \rightarrow Ni$$

C
$$Ni \rightarrow Ni^{2+} + 2e^-$$

D
$$2Al^{3+} + 6e^- \rightarrow 2Al$$

E
None of these

Solution

The half-reaction that occurs at the cathode is the reduction of Ni(II) ions to Ni atoms.

$$\displaystyle Ni^{2+} + 2e^- \rightarrow Ni $$

The gain of electrons is called reduction. Cathode is the electrode where reduction occurs. In the electrochemical series, Al (III) has more negative standard reduction potential than Ni (II).

Hence, Al is oxidized and Ni(II) is reduced.
Question 4
1 / -0

When current is passed through molten sodium chloride

A
sodium is deposited at the positive electrode and chlorine gas is formed at the negative electrode

B
sodium is evaporated and chloride ions and formed at the negative electrode

C
sodium is deposited at the positive electrode and chlorine is deposited at the negative electrode

D
sodium is deposited at the negative electrode and the chlorine gas is formed at the positive electrode

Solution

The electrolysis of sodium chloride $$(NaCl)$$ produces the positive ion, $$Na^+$$ and negative ions, $$Cl^-$$. Thus, the positive ion of sodium will be deposited at the negative electrode (cathode) and the chlorine ion will be deposited at the positive electrode (anode).
Question 5
1 / -0

When copper rod donates electrons to hydrogen ions, it gains ................. charge.

A
positie

B
negative

C
no charge

D
can't say

Solution

We know that when an atom donates electrons, the atom becomes positive charge and when the atom receives the electrons, it becomes negative charge.
Question 6
1 / -0

Copper electrode

A
donates electrons to hydrogen ions

B
accepts electrons from hydrogen ions

C
donates electrons to sulphate ions

D
accepts electrons from sulphate ions

Solution

According electron configuration of copper atom, there is one electron in the outermost shell. For becoming a stable atom, the copper electrode will donate electrons to hydrogen atom.
Question 7
1 / -0

Sulphate ions move towards

A
copper electrode

B
battery

C
electrolyte

D
zinc electrode

Solution

Sulphate ions move towards Zinc electrodes. Because negative ions move towards the positive electrode.They lose electrons and are oxidised.
Question 8
1 / -0

In electrolytic solutions, carrier of charge is

A
proton

B
electron

C
neutron

D
ion

Solution

An electrolyte is a substance that dissociates into ions in solution acquires the capacity to conduct electricity. Thus, electrolytic solutions contain only ions. So the charge carrier will be ion.
Question 9
1 / -0

An electrolyte

A
has positive charge

B
has negative charge

C
should be able to conduct charge without dissociating

D
should able to form positive and negative ions

Solution

The definition of electrolyte is a chemical compound that conducts electricity by changing into ions when melted or dissolved into a solution. Sodium, potassium, chloride are the examples of electrolyte. Sodium and potassium will form positive ions and chloride will form negative ions.
Question 10
1 / -0

In electrolysis

A
positive ions move towards the positive electrode and negative ions towards the negative electrode.

B
positive ions move towards the negative electrode and negative ions towards the positive electrode.

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

D
none of the above

Solution

In electrolysis, the positive ions produced are attracted towards the negative electrode. Thus positive ions move towards the negative electrode. Whereas, negative ions produced are attracted towards the positive electrode. Hence negative ions move towards the positive electrode.

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Electrochemistry Test - 35

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Electrochemistry Test - 35

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Question 1

When metal is gradually destroyed through chemical reactions

When metal is created through chemical reactions

When a redox reaction takes place

When a metal is destroyed after exposure to a gas

When a solid is destroyed through chemical reactions

Solution

Question 2

$$+1.10\ V$$

$$-1.10\ V$$

$$+1.07\ V$$

$$+1.14\ V$$

$$-1.07\ V$$

Solution

Question 3

$$Al \rightarrow Al^{3+} + 3e^-$$

$$Ni^{2+} + 2e^- \rightarrow Ni$$

$$Ni \rightarrow Ni^{2+} + 2e^-$$

$$2Al^{3+} + 6e^- \rightarrow 2Al$$

None of these

Solution

Question 4

sodium is deposited at the positive electrode and chlorine gas is formed at the negative electrode

sodium is evaporated and chloride ions and formed at the negative electrode

sodium is deposited at the positive electrode and chlorine is deposited at the negative electrode

sodium is deposited at the negative electrode and the chlorine gas is formed at the positive electrode

Solution

Question 5

positie

negative

no charge

can't say

Solution

Question 6

donates electrons to hydrogen ions

accepts electrons from hydrogen ions

donates electrons to sulphate ions

accepts electrons from sulphate ions

Solution

Question 7

copper electrode

battery

electrolyte

zinc electrode

Solution

Question 8

proton

electron

neutron

ion

Solution

Question 9

has positive charge

has negative charge

should be able to conduct charge without dissociating

should able to form positive and negative ions

Solution

Question 10

positive ions move towards the positive electrode and negative ions towards the negative electrode.

positive ions move towards the negative electrode and negative ions towards the positive electrode.

both ions move towards both the electrodes in equal amounts until they are balanced.

none of the above

Solution

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