Electrolysis and Electrolytic Cells Quiz

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Questions and Answers

What is the primary function of an electrolytic cell?

To store electricity for later use

To conduct electricity without any chemical changes

To drive non-spontaneous redox reactions using electric current (correct)

To generate electricity through spontaneous reactions

What characterizes an active electrode in an electrolytic cell?

It participates in the electrolytic process and its size changes (correct)

It never changes in size during the reaction

It allows current to pass without any chemical reaction

It absorbs electrons without participating in the reaction

During electrolysis, at which electrode does oxidation occur?

At the cathode, where reduction takes place

At the anode, where oxidation occurs (correct)

At both electrodes simultaneously

At a neutral electrode that does not participate

What is the significance of the electrolyte in an electrolytic cell?

It is the medium that allows ionic conduction and facilitates the reaction Signup and view all the answers

Which of the following devices primarily depends on electrochemical cells for operation?

Automobiles and smartphones Signup and view all the answers

What occurs at the cathode during electrolysis?

Reduction occurs Signup and view all the answers

Which of the following is a characteristic of a strong electrolyte?

It undergoes complete ionization in solution Signup and view all the answers

Which type of compound is considered a non-electrolyte?

Benzene Signup and view all the answers

What determines the discharge of ions during electrolysis?

The position of ions in the electrochemical series Signup and view all the answers

In electrolysis, which ions move towards the cathode?

Cations Signup and view all the answers

Which of the following is NOT a factor that influences the discharge of ions?

Color of the electrolyte Signup and view all the answers

What is the role of an electrolyte in electrolysis?

It acts as a conductor of electricity Signup and view all the answers

What happens to hydroxide ions (OH–) during the electrolysis of dilute NaCl?

They are oxidized at the anode. Signup and view all the answers

In the electrolysis of brine, which ion is discharged at the anode?

Chloride ions (Cl–) Signup and view all the answers

Which of the following statements about the electrolysis of molten NaCl is accurate?

Sodium metal (Na) is deposited at the cathode. Signup and view all the answers

Which ions migrate to the anode during the electrolysis of dilute NaCl?

Chloride (Cl-) and Hydroxide (OH-) Signup and view all the answers

During the anodic reaction in the electrolysis of dilute NaCl, what is the overall reaction involving hydroxide ions?

4OH– ⟶ O2 + 2H2O + 4e– Signup and view all the answers

What is the resulting solution after the electrolysis of dilute NaCl?

Neutral Signup and view all the answers

Which statement describes the discharge preference during electrolysis?

H+ is discharged over Na+ due to its lower electropositive nature. Signup and view all the answers

In the electrolysis of brine, which indicates a basic solution after the process?

Phenolphthalein turns pink. Signup and view all the answers

What is the overall reaction equation for the electrolysis of brine?

2 Cl– + 2H+ ⟶ Cl2 + H2 Signup and view all the answers

What determines the preferential discharge of ions during electrolysis?

The position of ions in the electrochemical series Signup and view all the answers

In a dilute NaCl solution, which ions are discharged at the anode?

OH– ions Signup and view all the answers

What happens when using a Hg cathode in the electrolysis of NaCl?

Na+ ions form Na amalgam with mercury Signup and view all the answers

Which cations are never discharged unless there is no competition for H+ or other cations?

Na+ and K+ Signup and view all the answers

Why are Cu atoms discharged during electrolysis of CuSO4 with a Cu anode?

Cu atoms give up electrons more readily than other ions Signup and view all the answers

What occurs with electrodes that are similar to the ions in the electrolyte?

They enter the solution during discharge Signup and view all the answers

How does the concentration of Cl– ions affect their discharge at the anode?

Higher concentration results in Cl– ions discharging before OH– ions Signup and view all the answers

What is the impact of the position of competing ions in the electrochemical series on electrolysis?

It influences preferential discharge Signup and view all the answers

What type of electrodes participate actively in the electrolysis process?

Active electrodes Signup and view all the answers

Study Notes

Electrochemistry

Electrochemistry involves chemical changes in chemical systems, including chemical reactions that produce electricity and the changes associated with current flow through matter.
Redox reactions (electron transfer) are central to these systems.
Metals can be purified or electroplated using electrochemical methods.
Devices like automobiles, smartphones, and many more use batteries for power.
All electrochemical systems involve electron transfer in a reacting system.
Reactions often occur in a region called a cell where electron transfer occurs at electrodes.

Electrolytic Cell

An electrolytic cell is an apparatus used for electrolysis.
It's a cell/device that produces chemical reactions through direct current flow.
A system of electrodes and electrolytes are used to drive non-spontaneous redox reactions.
This is a reaction system where a redox reaction happens with an electric current's help.

Electrolysis

Electrolysis is a process that uses electrical energy to induce a non-spontaneous chemical reaction.
It's the decomposition of an ionic system/electrolyte by direct electric current.
Electrolysis uses electric current to cause redox reactions.

Electrodes

Electrodes (anode and cathode) are metal strips or carbon plates (graphite) that allow current to enter or leave an electrolyte.
Electrodes can be active or inert.
Inert electrodes don't participate in the electrolytic reaction and their sizes stay the same (e.g., platinum, graphite).
Active electrodes do participate in the processes and their sizes change (e.g., Cu, Zn, Pb, Sn).

Anode

An anode is a positive electrode.
Current enters through it, or electrons leave the electrolyte.
Oxidation (loss of electrons) occurs at the anode.

Cathode

A cathode is a negative electrode.
Current leaves through it, or electrons enter the electrolyte.
Reduction (gain of electrons) occurs at the cathode.

Electrolyte

An electrolyte is a compound that conducts electricity in molten or aqueous states.
It decomposes in the electrolytic process.
Strong electrolytes completely ionize/dissociate in aqueous/molten states, good conductors of electricity. Examples: CuSO4, ZnSO4, HCl, H2SO4, HNO3, NaCl
Weak electrolytes only slightly/partially ionize, are poor conductors of electricity. Examples: H2O, NH3, CH3COOH, CH3NH2
Non-electrolytes do not ionize in aqueous/molten states and are non-conductors of electricity. Examples: sugar, benzene, alcohol

lonic Theory of Electrolysis

When an electrolyte is melted or dissolved in water, species dissociate into freely moving ions.
Anions move toward the anode (positive).
Cations move toward the cathode (negative).
The number of electrical charges carried by an ion equals its valency.

Mechanism of Electrolysis (Aqueous)

When the electrolyte is aqueous, it's dissociated with water.
For example, CuSO4 (aq) → SO42−(aq) + Cu2+(aq).
H2O → H+(aq) + OH−(aq)

Mechanism of Electrolysis (Molten)

When the electrolyte is molten, the electrolyte dissociates alone.
For example, CaCl2 → Ca2+(l) + 2Cl−(l)

Electrochemical Series

The electrochemical series arranges metallic elements/ions based on specified conditions.
It shows the tendency of one metal to reduce the ions of another below it in the series.
Cations (to cathode): K+, Na+, Ca2+, Mg2+, Al3+, Zn2+, Fe2+, Sn2+, Pb2+, H+, Cu2+, Hg2+, Ag+, Au+ (increasing preference for discharge/decreasing electropositivity)
Anions (to anode): F-, SO42-, NO3-, Cl-, Br-, I-, OH- (increasing preference for discharge/decreasing electronegativity)

Factors Influencing Discharge of Ions

Concentration of ions (higher concentration generally leads to easier discharge). The position of competing ions in the series is also important.
Nature of electrodes (active vs. inert).
Position of ions in the electrochemical series (less electropositive ions tend to discharge first).
Size and duration of current passed (affects the overall amount of ions discharged).

Electrolysis of Dilute NaCl

NaCl decomposes to Na+ and Cl-.
Water decomposes to H+ and OH-.
OH- are preferentially discharged at the anode.
H+ are discharged in preference to Na+ at the cathode.

Electrolysis of Brine (Concentrated NaCl)

This process leads to the discharge of Cl⁻ at the anode.
H+ discharge at the cathode, because H+ and Na+ are farther apart in the series, concentration does not count.

Electroplating

Electroplating coats an inferior metal with a superior one using electrolysis.
The object to be plated is the cathode.
The plating metal is the anode.
The electrolyte is a salt of the plating metal.

Purification of Metals

Electrolysis is a useful method for purifying metals.
Impure metal is the anode.
Pure metal is the cathode.
A solution of a soluble salt of the metal serves as the electrolyte.

Faraday's Laws of Electrolysis

Law 1: The mass of a substance liberated or deposited at an electrode during electrolysis is directly proportional to the quantity of electricity passed. (m ∝ Q)
Law 2: When the same quantity of electricity is passed through different electrolytes, the masses of the substances liberated or deposited are proportional to their equivalent masses. (m ∝ E).

Factors Affecting the Amount of Products Deposited

Magnitude of the steady current passed
Duration of the steady current
Ionic charges of the liberated element

Important Applications of Electrolysis

Electroplating
Extraction of metals
Purification of metals
Production of chemicals (e.g., H2, O2, Cl2, NaOH)

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Description

Test your knowledge on the fundamental concepts of electrolytic cells and electrolysis. This quiz covers the primary functions of electrolytic cells, the characteristics of active electrodes, oxidation processes, and the importance of electrolytes. Perfect for students learning about electrochemistry.