Chemistry Reactions and Electrolysis

These flashcards summarize key concepts from the lecture about oxidation, reduction, the reactivity series of metals, electrolysis, and related chemical reactions.

What is oxidation?

Oxidation is when a substance gains oxygen.

What is reduction?

Reduction is when a substance loses oxygen.

What does the reactivity series of metals show?

It shows the metals in order of their reactivity.

Which metals react with acid to produce hydrogen?

Metals above H2 in the reactivity series.

What happens to more reactive metals when they react with acid?

The reaction occurs quickly and violently.

What is the reactivity of metals below hydrogen?

They do not react with acids.

Which groups of metals mostly react with water?

Group I and II metals.

What is a displacement reaction?

A reaction where a more reactive metal displaces a less reactive metal from a compound.

How can metals less reactive than carbon be extracted?

By reduction with carbon.

What happens during the reduction process with carbon?

Carbon displaces the metal in a metal oxide and gets oxidised to carbon oxides.

How are oxidation and reduction defined in terms of electron transfer?

Oxidation is the loss of electrons; reduction is the gain of electrons.

What is the general equation for a reaction between metals and acids?

Metal + acid → salt + hydrogen.

What type of reaction occurs between metals and acids?

A redox reaction, also a displacement reaction.

What is the general equation for the reaction between metal carbonate and acid?

Metal carbonate + acid → salt + water + carbon dioxide.

What is the general equation for the reaction between metal oxides and acids?

Metal oxide + acid → salt + water.

What happens to magnesium when it reacts with hydrochloric acid?

Magnesium loses electrons and is oxidised; hydrogen gains electrons and is reduced.

How is a soluble salt formed?

a) React excess acid with some insoluble substance, b) Filter off leftovers, c) Crystallise the product.

What are bases, acids, and alkalis?

Bases neutralise acids; acids produce hydrogen ions; alkalis are soluble bases producing hydroxide ions.

What is the pH scale?

The measure of acidity/alkalinity of a solution.

What does a pH of 7 indicate?

It indicates a neutral solution.

What is the general equation for a neutralisation reaction?

H+ + OH− → H2O.

What is a strong acid?

A strong acid is completely ionised in aqueous solution.

What is a weak acid?

A weak acid is only partially ionised in aqueous solution.

What is a concentrated acid?

A concentrated acid has more moles of acid per unit volume than a dilute acid.

What is a dilute acid?

A dilute acid refers to solutions of low concentrations.

Is concentration the same as strength of an acid?

No, concentration is not the same as strength.

What happens to hydrogen ion concentration as pH decreases by one unit?

It increases by a factor of 10.

Name the following salts: LiNO3, K2CO3, MgBr2, BaSO4.

Lithium nitrate, Potassium carbonate, Magnesium bromide, Barium sulfate.

What is electrolysis?

The process of passing an electric current through ionic substances to break them down into elements.

What is a cathode?

The cathode is the negative electrode.

What is an anode?

The anode is the positive electrode.

What occurs at the cathode during electrolysis?

Reduction occurs at the cathode.

What occurs at the anode during electrolysis?

Oxidation occurs at the anode.

What happens if a less reactive element is present during aqueous electrolysis?

The less reactive element discharges at the cathode.

What produces oxygen at the anode unless halide ions are present?

Oxygen is produced at the anode.

How is aluminium manufactured?

Aluminium is made through the electrolysis of aluminium oxide and cryolite.

Why is aluminium manufacturing expensive?

It requires a lot of energy to produce the current needed for electrolysis.

What are the half equations in the extraction of aluminium?

Al3+ + 3 e− → Al (cathode); 2 O2− → O2 + 4 e− (anode).

Why is cryolite used in aluminium manufacturing?

It lowers the melting point of aluminium oxide, reducing energy costs.

What are the half equations in the electrolysis of aqueous Na2SO4?

2 H+ + 2 e− → H2 (cathode); 4 OH− → 2 H2O + O2 + 4 e− (anode).

What are the half equations in the electrolysis of molten and aqueous KCl?

K+ + e− → K (cathode); 2 Cl− → Cl2 + 2 e− (anode).

What are the half equations in the electrolysis of aqueous CuBr2?

Cu2+ + 2 e− → Cu (cathode); 2 Br− → Br2 + 2 e− (anode).