Redox reactions

Freesciencelessons

Write the formula for ethanoic acid

CH3COOH

Which element does all acids contain?

Hydrogen

What happens when we dissolve an acid in water?

Hydrogen is released as the hydrogen ion H+

What does it mean when we say that an acid molecule ‘dissociates’?

It splits

When an acid molecule dissociates, what two ions are released?

Positive and negative ion

• eg. HCl = H+ + Cl-

Why would HCL, for example, be considered a strong acid?

Because every acid molecule dissociates and releases the hydrogen ion.

Name the 3 main strong acids

• Hydrochloric

• Nitric

• Sulfuric

Why would CH3COOH, for example, be considered a weak acid?

• Because only a small percentage of the acid molecules dissociates- meaning it only partially dissociates

What 3 type of metal compounds do bases include?

• Metal oxides

• Metal hydroxides

• Metal carbonates

How do we know when a substance is a base?

It can neutralise an acid to make a salt

What 3 products are formed when a metal carbonate reacts with an acid?

• Salt

• Water

• Carbon dioxide

Difference between base and alkali

• Base- any substance that can neutralise an acid

• Alkali- aqueous base that dissociates in water and releases OH- ions

Which group of metal hydroxides are soluble in water? (and can thus form alkalis)

Group 1 (i.e Na, K, Li)

What 2 products are formed when an alkali reacts with an acid?

Salt and water

What are redox reactions?

Reactions where both reduction and oxidation have occured

Explain reduction and oxidation in terms of hydrogen

• Oxidation- loss of hydrogen

• Reduction- gain of hydrogen

Explain reduction and oxidation in terms of oxygen

• Oxidation- gain of oxygen

• Reduction- loss of oxygen

What are spectator ions in reactions?

Ions that do not gain or lose electrons throughout the reaction

Explain reduction and oxidation in terms of electrons

• Oxidation is loss of electrons

• Reduction is gain of electrons (OILRIG)

What is the oxidising agent in a redox reaction?

The chemical accepting the electrons

eg. Zn2+ + 2e- = Zn

What is the reducing agent in a redox reaction?

The chemical donating the electrons

eg. Mg = Mg2+ + 2e-

Fill in the blank:

The oxidising agent is_ and the reducing agent is _

• The oxidising agent is reduced

• The reducing agent is oxidised