Electrochemistry Flashcards
1
Q
What is Electrochemistry?
A
The study of chemical changes that occur when electric current is passed through a material or chemical reactions that produce electric current.
2
Q
What does Electrochemistry deal with?
A
The interconversion of electrical energy and chemical energy.
3
Q
Give an example of electrochemistry in daily life.
A
Rusting of iron, combustion of fuel, and food metabolism in humans and animals.
4
Q
What kind of reactions are involved in electrochemical processes?
A
Oxidation-reduction (redox) reactions.
5
Q
What happens during a redox reaction?
A
There is a transfer of electrons between substances.
6
Q
Why is electrochemistry important?
A
It helps in understanding batteries, corrosion, electroplating, and biological energy transfer.
7
Q
True or False: Electrochemistry only deals with producing electricity.
A
False
8
Q
Which of the following is NOT an application of electrochemistry?
A
A) Batteries B) Electroplating C) Photosynthesis D) Corrosion
9
Q
Fill in the blank: The loss of electrons is called ___.
A
Oxidation
10
Q
Fill in the blank: The gain of electrons is called ___.
A
Reduction
11
Q
What is the process in which electrical energy is converted into chemical energy?
A
Electrolysis
12
Q
What is the process in which chemical energy is converted into electrical energy?
A
Electrochemical cell or battery
13
Q
What happens to electrons in oxidation?
A
Electrons are lost
14
Q
What happens to electrons in reduction?
A
Electrons are gained
15
Q
True or False: Oxidation and reduction always occur together in a redox reaction.
A
True
16
Q
Which of the following is an oxidation reaction?
A
A) Fe²⁺ + 2e⁻ → Fe B) C + O₂ → CO₂ C) Ag⁺ + e⁻ → Ag
17
Q
Which of the following is a reduction reaction?
A
A) 2NH₃ + 3I₂ → N₂ + 6HI B) Fe → Fe²⁺ + 2e⁻ C) H₂O → H₂ + O₂
18
Q
Fill in the blank: The removal of oxygen from a compound is called ___.
A
Reduction
19
Q
Fill in the blank: The addition of oxygen to a compound is called ___.
A
Oxidation
20
Q
True or False: Oxidation involves gaining electrons.
A
False
21
Q
Fireflies produce light due to the oxidation of which chemical?
A
Luciferin
22
Q
What happens to HgO when heated?
A
It is reduced to Hg
23
Q
Which of the following describes oxidation?
A
A) Loss of electrons B) Gain of electrons C) No change in electrons
24
Q
What is a redox reaction?
A
A reaction where oxidation and reduction occur simultaneously.
25
What is oxidation in terms of hydrogen?
The removal of hydrogen from a compound.
26
What is the addition of hydrogen to a substance called?
Reduction
27
What is the addition of electrons to a substance called?
Reduction
28
In the reaction between sodium (Na) and chlorine (Cl), what happens to sodium (Na)?
Sodium loses an electron and is oxidized to sodium ion (Na⁺)
29
In the reaction between sodium (Na) and chlorine (Cl), what happens to chlorine (Cl)?
Chlorine gains an electron and is reduced to chloride ion (Cl⁻)
30
What is a redox reaction?
A reaction where oxidation and reduction occur simultaneously
31
True or False: Oxidation states or oxidation numbers have an exact physical meaning.
False
32
What is the purpose of oxidation numbers?
They are used in naming compounds, writing formulas, and balancing chemical equations
33
Fill in the blank: Oxidation numbers do not have an exact physical meaning, but they are useful for ___.
Naming compounds, writing formulas, and balancing chemical equations
34
Fill in the blank: The color of solutions changes with the change of ___.
Oxidation state
35
What does the color change of a chromium solution indicate?
It indicates a change in the oxidation state
36
What is the oxidation state of chromium in Cr₂O₇²⁻?
6
37
Multiple Choice: What happens to an atom in a reduction process?
A) It gains electrons B) It loses electrons C) It gains hydrogen
38
Multiple Choice: Which of the following describes the oxidation process?
A) Loss of electrons B) Gain of electrons C) Loss of hydrogen
39
What is the oxidation number of all elements in the free state?
Zero
40
What is the oxidation number of a simple ion?
The same as the charge on the ion
41
What is the oxidation number of hydrogen in its compounds?
+1, except in metal hydrides where it is -1
42
What is the oxidation number of oxygen in its compounds?
-2, except in peroxides where it is -1
43
What is the oxidation number of elements in Group I, II, and III?
+1, +2, and +3 respectively
44
What is the oxidation number of halogens in their binary compounds?
-1
45
In neutral molecules, what is the algebraic sum of the oxidation numbers?
Zero
46
In ions, what is the algebraic sum of oxidation numbers?
Equal to the charge on the ion
47
True or False: The oxidation number of a substance is always constant.
False
48
What is an oxidizing agent?
A substance that oxidizes another substance and itself gets reduced
49
What is a reducing agent?
A substance that reduces another substance and itself gets oxidized
50
Multiple Choice: What is the oxidation number of sulfur in SO₄²⁻?
A) +6 B) +2 C) -6
51
Multiple Choice: What is the oxidation number of chlorine in NaCl?
A) +1 B) -1 C) 0
52
Fill in the blank: In a redox reaction, the donor of electrons is the ___.
Reducing agent
53
Fill in the blank: The oxidation state of manganese in MnO₄⁻ is ___.
7
54
Multiple Choice: What happens to the oxidation number of a substance when it acts as an oxidizing agent?
A) It increases B) It decreases C) It stays the same
55
What is the oxidation number of carbon in CO₂?
4
56
Consider the reaction: Zn + CuO → Cu + ZnO. What is the oxidation number of Cu in CuO?
2
57
What is the oxidizing agent in the reaction Zn + CuO → Cu + ZnO?
CuO
58
Consider the reaction: Sn + Cl₂ → SnCl₂. What is the oxidation number of Cl in Cl₂?
59
What is the reducing agent in the reaction Sn + Cl₂ → SnCl₂?
Cl₂
60
What is a reducing agent?
A substance that reduces another substance and itself gets oxidized
61
What does a reducing agent donate?
Hydrogen or electrons
62
In the reaction H₂S → S + 2e⁻, what happens to the oxidation number of sulfur (S)?
It increases from -2 to 0
63
What is the oxidation number of sulfur in H₂S?
-2
64
In the reaction H₂S → S + 2e⁻, is H₂S a reducing agent or oxidizing agent?
Reducing agent
65
Multiple Choice: What is an example of a reducing agent?
A) Potassium permanganate B) Hydrogen sulfide C) Oxygen
66
Multiple Choice: What is an example of an oxidizing agent?
A) Bromine B) Hydrogen C) Carbon monoxide
A) Bromine
67
Fill in the blank: Ozone is a very strong ___.
Oxidizing agent
68
Fill in the blank: The process of using oxygen to oxidize organic materials in wastewater is called ___.
Wet oxidation
69
What are redox reactions?
Chemical reactions where oxidation (loss of electrons) and reduction (gain of electrons) occur simultaneously
70
In redox reactions, how are the half-reactions written?
One for oxidation (electron loss) and one for reduction (electron gain)
71
Multiple Choice: In the reaction ZnSO₄(aq) + Cu(s) → CuSO₄(aq) + Zn(s), what happens to zinc (Zn)?
A) It gets oxidized B) It gets reduced C) It stays the same
A) It gets oxidized
72
In a redox reaction, what happens to the substance that gets reduced?
Its oxidation number decreases
73
Multiple Choice: What is the oxidation number of chlorine (Cl) in NaCl?
A) 0 B) -1 C) +1
B) -1
74
In a half-reaction, when electrons are lost, what is this called?
Oxidation
75
In a half-reaction, when electrons are gained, what is this called?
Reduction
76
What causes oxidation in a reaction?
Oxidizing agent
77
What happens to a substance in oxidation?
It loses electrons
78
In a redox reaction, what happens to the substance that is reduced?
It gains electrons
79
What is an electrochemical cell?
A device in which chemical reactions take place to produce electric current or use electric current to drive chemical reactions
80
What are the two types of electrochemical cells?
Voltaic cells (galvanic cells) and electrolytic cells
81
What is an electrolyte?
A substance that dissociates into ions and conducts electricity in solution or molten state
82
Multiple Choice: Which of the following is an example of a strong electrolyte?
A) NaCl B) CH₃COOH C) Glucose
A) NaCl
83
Multiple Choice: Which of the following is an example of a weak electrolyte?
A) NaCl B) CH₃COOH C) NaOH
B) CH₃COOH
84
Fill in the blank: Strong electrolytes dissociate or ionize ___ in solution or molten state.
Completely
85
What are non-electrolytes?
Substances that do not dissociate into ions and do not conduct electricity
86
Multiple Choice: Which of the following is an example of a non-electrolyte?
A) Benzene B) NaCl C) H₂SO₄
A) Benzene
87
What is the function of electrodes in an electrochemical cell?
To conduct electricity and allow electrons to enter or leave the electrolyte
88
What is the anode in an electrolytic cell?
The positive electrode where the anion gathers and electrons leave
89
Multiple Choice: In an electrolytic cell, which of the following particles is attracted to the anode?
A) Cations B) Anions C) Electrons
B) Anions
90
What is a reducing agent in a redox reaction?
A substance that donates electrons and itself gets oxidized
91
What happens to the oxidation number of a reducing agent during a redox reaction?
It increases
92
Fill in the blank: In a redox reaction, the substance that gets reduced has a decrease in its ___ number.
Oxidation
93
What happens at the cathode in an electrolytic cell?
Cations gather and gain electrons
94
What happens at the anode in an electrolytic cell?
Anions liberate electrons
95
What is electrolysis?
The process of using electrical energy to drive a non-spontaneous oxidation-reduction reaction
96
In an electrolytic cell, what is the role of the anode?
The anode is the positive electrode where oxidation takes place and electrons are lost
97
In an electrolytic cell, what is the role of the cathode?
The cathode is the negative electrode where reduction takes place and electrons are gained
98
Fill in the blank: In an electrolytic cell, the number of electrons lost is always equal to the number of electrons ___.
Gained
99
Multiple Choice: Which of the following is true about an electrolytic cell?
A) It uses electrical energy to drive a non-spontaneous reaction B) It produces electricity from a spontaneous reaction
A) It uses electrical energy to drive a non-spontaneous reaction
100
What is required for an oxidation-reduction reaction to occur in an electrolytic cell?
Electrical energy
101
What is the electrolyte in an electrolytic cell?
A substance that dissociates into ions when molten or in solution and conducts electricity
102
Multiple Choice: Which of the following is a common example of an electrolytic cell?
A) Downs cell B) Galvanic cell C) Lead-acid battery
A) Downs cell
103
Fill in the blank: Electrolytic cells consist of two electrodes, the anode and the ___.
Cathode
104
Multiple Choice: What happens when electrical current is passed through a solution in an electrolytic cell?
A) The ions move toward their respective electrodes B) The solution becomes neutral C) The electrodes dissolve completely
A) The ions move toward their respective electrodes
105
What happens when cations surround the cathode in an electrolytic cell?
They gain electrons
106
In the process of electrolysis, what do anions do at the anode?
Liberate electrons
107
Fill in the blank: The electrolytic cell consists of a solution of an electrolyte and two electrodes, the anode and the ___.
Cathode
108
Multiple Choice: Which of the following metals are commonly used as electrical conductors in wiring?
A) Gold B) Copper C) Silver
B) Copper
109
Which substances are considered non-electrolytes?
Substances that do not dissociate or ionize in solution and do not conduct electricity
110
What is the role of the battery in an electrolytic cell?
The battery acts as an electron pump, supplying electrons to the cathode and receiving electrons from the anode
111
Multiple Choice: What happens at the anode in an electrolytic cell?
A) Reduction takes place B) Oxidation takes place
B) Oxidation takes place
112
Multiple Choice: What happens at the cathode in an electrolytic cell?
A) Reduction takes place B) Oxidation takes place
A) Reduction takes place
113
What is the overall reaction when electric current passes through fused sodium chloride (NaCl)?
2NaCl → 2Na + Cl2
114
Fill in the blank: In the electrolytic cell, at the anode, oxidation occurs when ___ ions lose electrons.
Cations
115
Fill in the blank: In the electrolytic cell, at the cathode, reduction occurs when ___ ions gain electrons.
Anions
116
What is the purpose of electrochemical purification of metals?
To purify metals like copper using electro-refining
117
Multiple Choice: What is the process of refining copper called?
A) Electro-refining B) Electrolysis C) Electroplating
A) Electro-refining
118
What is the electrolyte used in the purification of copper?
Copper Sulphate (CuSO4)
119
Multiple Choice: What metals are typically dissolved during the electro-refining of copper?
A) Less active metals like Zn, Fe B) Copper itself C) Silver and Gold
A) Less active metals like Zn, Fe
120
Fill in the blank: During electro-refining, copper ions from the solution are reduced at the ___ to form metallic copper.
Cathode
121
Multiple Choice: What is the final purity of copper obtained through electro-refining?
A) 99.9% B) 99.99% C) 100%
B)99.99%
122
What is the product obtained from the sludge at the bottom of an electrolytic cell during copper purification?
Precious metals like gold (Au) and silver (Ag)
123
What happens to impurities like zinc and iron during copper purification by electrolysis?
They dissolve in the solution
124
What is a Voltaic cell?
A cell where a spontaneous redox reaction produces electrical energy
125
What is the purpose of a Galvanic (Voltaic) cell?
To convert chemical energy into electrical energy
126
What is the most common example of a Voltaic cell?
The Daniel cell
