Ib Chemistry Hl Topic 9

1. Deduce whether an element undergoes oxidation or reduction in reactions using oxidation numbers.

LEORA: loss electrons, oxidation, reducing agentGEROA: gain electrons, reduction, oxidizing agent
Look at oxidation numbers of elements on both sides of chemical equations.

BEROA: balance electrons, both oxidation and reduction, neutral agent

TEGOA: take electrons, gain oxidation, reducing agent

MEROA: maintain electrons, no change, neutral agent

In order to determine whether an element undergoes oxidation or reduction in reactions using oxidation numbers, it is important to understand the principles behind LEORA and GEROA. These incorrect answers provide alternative options that may confuse individuals who are trying to deduce oxidation or reduction reactions.

Explanation

In order to determine whether an element undergoes oxidation or reduction in reactions using oxidation numbers, it is important to understand the principles behind LEORA and GEROA. These incorrect answers provide alternative options that may confuse individuals who are trying to deduce oxidation or reduction reactions.

2. Deduce simple oxidation and reduction half-equations given the species involved in a redox reaction.

Examine the full balanced equation.

Consider the colors of the substances involved.

Look at half equations.
These equations are known as half equations and for aredox reaction the half equations for the substance beingoxidized and the substance being reduced can be combinedin such a way that the electrons cancel out, so as to give abalanced equation for the redox reaction.

Use a calculator to determine the half-equations.

When deducing oxidation and reduction half-equations for a redox reaction, it is important to focus on the half equations rather than the full balanced equation, colors, or using a calculator.

Explanation

When deducing oxidation and reduction half-equations for a redox reaction, it is important to focus on the half equations rather than the full balanced equation, colors, or using a calculator.

3. Deduce redox equations using half-equations.

Half-equations do not need to be balanced in redox reactions.

H+ and H2O should be used where necessaryto balance half-equations in acid solution. Thebalancing of equations for reactions in alkalinesolution will not be assessed.

Balancing of equations for reactions in alkaline solution is required for full credit.

Only H2O is needed to balance half-equations in acid solution.

When deducing redox equations using half-equations, it is important to utilize H+ and H2O to balance the equations in acid solution. Balancing equations in alkaline solution is not necessary for assessment purposes. Incorrect answers provide information that does not align with the standard practice of balancing half-equations in redox reactions.

Explanation

When deducing redox equations using half-equations, it is important to utilize H+ and H2O to balance the equations in acid solution. Balancing equations in alkaline solution is not necessary for assessment purposes. Incorrect answers provide information that does not align with the standard practice of balancing half-equations in redox reactions.

4. Define the terms oxidizing agent and reducing agent.

Reducing agent: A substance that gains electrons.

Reducing agent: A substance that increases oxidation numbers of other substances.

Oxidizing agent: A substance that loses electron.

Oxidising agent: An oxidising agent is itself reduced, that is it is a substance that can accept electronsfrom another substance or increase the oxidation numbers in another substance. Reducing agent: A reducing agent is itself oxidised, that is it is a substance that can donate electronsto another substance or decrease the oxidation numbers in another substance.

Oxidizing agent: A substance that decreases the oxidation numbers of other substances.

The correct definitions of oxidizing agent and reducing agent involve the concepts of electron transfer and oxidation numbers as described in the correct answer. The incorrect answers provided do not accurately define these terms.

Explanation

The correct definitions of oxidizing agent and reducing agent involve the concepts of electron transfer and oxidation numbers as described in the correct answer. The incorrect answers provided do not accurately define these terms.

5. Identify the oxidizing and reducing agents in redox equations.

LEORA: loss electrons, oxidation, reducing agentGEROA: gain electrons, reduction, oxidizing agent

EROLA: gain electrons, reduction, reducing agent, LAGERO: loss electrons, oxidation, oxidizing agent

ORLEA: oxidation, reduction, oxidizing agent, EGLORA: electrons gain, loss, reducing agent

GEOAR: gain electrons, oxidation, oxidizing agent, LEROA: loss electrons, reduction, reducing agent

In redox reactions, the oxidizing agent gets reduced by accepting electrons while the reducing agent gets oxidized by losing electrons. The correct answer provides a mnemonic device 'LEORA' for loss electrons, oxidation, reducing agent and 'GEROA' for gain electrons, reduction, oxidizing agent.

Explanation

In redox reactions, the oxidizing agent gets reduced by accepting electrons while the reducing agent gets oxidized by losing electrons. The correct answer provides a mnemonic device 'LEORA' for loss electrons, oxidation, reducing agent and 'GEROA' for gain electrons, reduction, oxidizing agent.

6. 9.3.1: Deduce a reactivity series based on the chemical behaviour of a group of oxidizing and reducing agents.

Identifying isotopes to establish reactivity series.

Analyzing atomic number to rank reactivity series.

Using standard electrode potentials to determine reactivity series.

Refer to image. Examples include displacement reactions of metalsand halogens. Standard electrode potentials will notbe assessed.

7. Deduce the feasibility of a redox reaction from a given reactivity series.

Students are not expected to recall a specificreactivity series. Reactivity series: A simplified form of a table of standard electrode potentials, this shows the relativereactivities (and spontaneities) of a set of chemicals.

Only professionals in the field of chemistry can deduce the feasibility of redox reactions.

Students must memorize the reactivity series for every redox reaction.

The reactivity series does not impact the feasibility of redox reactions.

The feasibility of a redox reaction can be deduced from a reactivity series, which is a simplified form of a table of standard electrode potentials showing the relative reactivities of chemicals. However, students are not expected to recall a specific reactivity series, as understanding the concept is sufficient.

Explanation

The feasibility of a redox reaction can be deduced from a reactivity series, which is a simplified form of a table of standard electrode potentials showing the relative reactivities of chemicals. However, students are not expected to recall a specific reactivity series, as understanding the concept is sufficient.

8. Explain how a redox reaction is used to produce electricity in a voltaic cell.

The more reactive metal will always be the positive electrode in a voltaic cell.

This should include a diagram to show how twohalf-cells can be connected by a salt bridge.Examples of half-cells are Mg, Zn, Fe and Cu insolutions of their ions.
A Voltaic (Galvanic or electrochemical) cell is a device forconverting chemical energy into electrical energy using aspontaneous redox reaction as a source of electrical energyand this is the basis of commercial electrochemical cells(batteries). The opposite, which uses electrical energy tocarry out a non-spontaneous redox reaction is known aselectrolysis.
The more reactive metal will always be the negativeelectrode and the greater the difference in reactivity ofthe metals, the greater the cell potential. A high resistancevoltmeter connected between the metals will measurethe potential difference between them.

Using a voltaic cell mainly involves the exchange of heat energy rather than electrical energy.

Voltaic cells are mainly used to separate mixtures of substances rather than producing electricity.

A voltaic cell converts chemical energy into electrical energy through a spontaneous redox reaction. The more reactive metal is the negative electrode, not the positive electrode, and the cell is used specifically for producing electricity and not for separating mixtures or exchanging heat energy.

Explanation

A voltaic cell converts chemical energy into electrical energy through a spontaneous redox reaction. The more reactive metal is the negative electrode, not the positive electrode, and the cell is used specifically for producing electricity and not for separating mixtures or exchanging heat energy.

9. State the correct location where oxidation and reduction occur in an electrolytic cell.

Oxidation occurs at the positive electrode (cathode) and reduction occurs at the negative electrode (anode).

Oxidation and reduction both occur at the negative electrode (anode).

Oxidation and reduction both occur at the positive electrode (cathode).

Simple state.

In an electrolytic cell, oxidation always occurs at the anode (negative electrode) where electrons are lost, and reduction occurs at the cathode (positive electrode) where electrons are gained. This is a fundamental principle in electrochemistry.

Explanation

In an electrolytic cell, oxidation always occurs at the anode (negative electrode) where electrons are lost, and reduction occurs at the cathode (positive electrode) where electrons are gained. This is a fundamental principle in electrochemistry.

10. Describe, using a diagram, the essential components of an electrolytic cell.

The diagram should include the source of light energy and reflectors, positive and negative electrodes, and the electrolyte.

The diagram should include the source of heat and reactants, positive and negative electrodes, and the electrolyte.

The diagram should include the source of mechanical energy and gears, positive and negative electrodes, and the electrolyte.

The diagram should include the source of electriccurrent and conductors, positive and negativeelectrodes, and the electrolyte.
In electrolysis electrical energy is used to bring about anon-spontaneous redox reaction. This is done by passingan electric current through a liquid containing ions, knownas an electrolyte. In contrast to metals, the current inelectrolytes is carried by the movement of ions rather thanthe movement of electrons.
Electrolysis: A process in which electrical energy is used to cause a non-spontaneous chemicalreaction to occur. Electrolytic cell: The cell in which electrolysis occurs. The cell contains the anode (positive), cathode(negative) and the electrolyte.

Electrolytic cells require electrical energy, not heat, light, or mechanical energy, to drive the non-spontaneous chemical reactions involved in electrolysis.

Explanation

Electrolytic cells require electrical energy, not heat, light, or mechanical energy, to drive the non-spontaneous chemical reactions involved in electrolysis.

11. Where does oxidation occur in an electrochemical cell?

Negative electrode (cathode)

State.

Center of the cell

External wires connecting the electrodes

In an electrochemical cell, oxidation occurs at the positive electrode, which is called the anode. Reduction occurs at the negative electrode, known as the cathode. Electrons flow from the anode to the cathode through the external wires connecting the electrodes.

Explanation

In an electrochemical cell, oxidation occurs at the positive electrode, which is called the anode. Reduction occurs at the negative electrode, known as the cathode. Electrons flow from the anode to the cathode through the external wires connecting the electrodes.

12. Describe how current is conducted in an electrolytic cell.

In an electrolytic cell, there are no electrodes involved in conducting current.

He solid conductors insertedinto the liquid are called electrodes, the one with a positivecharge is called the anode (because it attracts anions) andthe one with the negative charge is called the cathode.When the anions reach the anode they lose electrons andare therefore oxidized (LEO). Similarly when the cationsreach the cathode they gain electrons and are thereforereduced (GER).

Current is conducted through the liquid by ions moving from the anode to the cathode.

The current is conducted by electrons moving from the cathode to the anode.

13. Deduce the products of the electrolysis of a molten salt.

Oxygen and hydrogen gases are released

Half-equations showing the formation of productsat each electrode will be assessed. Aim 8: This process (which required the discoveryof electricity) has made it possible to obtainreactive metals such as aluminium from theirores. This in turn has enabled subsequent steps in engineering and technology that increase ourquality of life. Unlike iron, aluminium is not prone tocorrosion and is one material that is replacing ironin many of its applications.
Electrolysis of a molten electrolyte is often used to obtainreactive metals from their ores.

Sodium chloride is regenerated

A copper and zinc alloy is formed

Electrolysis of a molten electrolyte is often used to obtain reactive metals from their ores. Half-equations showing the formation of products at each electrode will be assessed to determine the products of the electrolysis process.

Explanation

Electrolysis of a molten electrolyte is often used to obtain reactive metals from their ores. Half-equations showing the formation of products at each electrode will be assessed to determine the products of the electrolysis process.