International Baccalaureate IB Chemistry

Oxidation and reduction can be described in terms of electron transfer, change in oxidation state, oxygen gain/loss or hydrogen loss/gain.

Deduce oxidation states of an atom in a compound or an ion. 

Identify the oxidized and reduced species and the oxidizing and reducing agents in a chemical reaction.

Half-equations separate the processes of oxidation and reduction, showing the loss or gain of electrons.

Deduce redox half-equations and equations in acidic or neutral solutions. 

Tool 1, Inquiry 2—Why are some redox titrations described as “self-indicating”.

The relative ease of oxidation and reduction of an element in a group can be predicted from its position in the periodic table.

The reactions between metals and aqueous metal ions demonstrate the relative ease of oxidation of different metals. 

Predict the relative ease of oxidation of metals. Predict the relative ease of reduction of halogens. Interpret data regarding metal and metal ion reactions.

Acids react with reactive metals to release hydrogen.

Deduce equations for reactions of reactive metals with dilute and .

Oxidation occurs at the anode and reduction occurs at the cathode in electrochemical cells.

Identify electrodes as anode and cathode, and identify their signs/polarities in voltaic cells and electrolytic cells, based on the type of reaction occurring at the electrode.

A primary (voltaic) cell is an electrochemical cell that converts energy from spontaneous redox reactions to electrical energy.

Explain the direction of electron flow from anode to cathode in the external circuit, and ion movement across the salt bridge.

Secondary (rechargeable) cells involve redox reactions that can be reversed using electrical energy.

Deduce the reactions of the charging process from given electrode reactions for discharge, and vice versa.

An electrolytic cell is an electrochemical cell that converts electrical energy to chemical energy by bringing about non-spontaneous reactions.

Explain how current is conducted in an electrolytic cell. Deduce the products of the electrolysis of a molten salt.

Functional groups in organic compounds may undergo oxidation.

Deduce equations to show changes in the functional groups during oxidation of primary and secondary alcohols, including the two-step reaction in the oxidation of primary alcohols.

$$\text{Primary alcohol:}\quad RCH_2OH \xrightarrow{\text{[O]}} RCHO \xrightarrow{\text{[O]}} RCOOH$$

$$\text{Secondary alcohol:}\quad R_2CHOH \xrightarrow{\text{[O]}} R_2C=O$$

Functional groups in organic compounds may undergo reduction.

Deduce equations to show reduction of carboxylic acids to primary alcohols via the aldehyde, and reduction of ketones to secondary alcohols. 

$$\ce{R-COOH + 2\,\text{[H]} -> R-CHO + H2O}$$
$$\ce{R-CHO + \text{[H]} -> R-CH2OH}$$
Overall: $$\ce{R-COOH + 4\,\text{[H]} -> R-CH2OH + H2O}$$

$$\ce{R2C=O + \text{[H]} -> R2CHOH}$$

Include the role of hydride ions in the reduction reaction. 

The hydride ion $\ce{H-}$, delivered by reagents such as $\ce{LiAlH4}$ or $\ce{NaBH4}$, acts as the nucleophilic reducing agent that transfers a hydride to the carbonyl carbon in each step.

Reduction of unsaturated compounds by the addition of hydrogen lowers the degree of unsaturation.

Deduce the products of the reactions of hydrogen with alkenes and alkynes.

The hydrogen half-cell $ \mathrm{H}^+ (aq) + e^- \rightleftharpoons \frac{1}{2}\,\mathrm{H}_2 (g) $ is assigned a standard electrode potential of zero by convention. It is used in the measurement of standard electrode potential, $E^\circ$.

Interpret standard electrode potential data in terms of ease of oxidation/reduction.

Standard cell potential, $E^\circ_{\text{cell}}$, can be calculated from standard electrode potentials. $E^\circ_{\text{cell}}$ has a positive value for a spontaneous reaction.

Predict whether a reaction is spontaneous in the forward or reverse direction from $E^\circ$ data.

The equation $ \Delta G^\circ = -nF E^\circ_{\text{cell}} $ shows the relationship between standard Gibbs energy and standard cell potential for a reaction.

Determine the value for $ \Delta G^\circ $ from $ E^\circ $ data. 

The equation and the value of $ F $ in C mol$^{-1}$ are given in the data booklet.

During electrolysis of aqueous solutions, competing reactions can occur at the anode and cathode, including the oxidation and reduction of water.

Deduce from standard electrode potentials the products of the electrolysis of aqueous solutions.

Electroplating involves the electrolytic coating of an object with a metallic thin layer.

Deduce equations for the electrode reactions during electroplating.