Edexcel IGCSE Chemistry - Paper 2 Flashcards
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Questions and Answers

What is the reason for giant ionic structures having high melting and boiling points?

  • Covalent bonds
  • Weak intermolecular forces
  • Presence of free electrons
  • Electrostatic attraction between oppositely charged ions is very strong (correct)

How many other atoms is a carbon atom covalently bonded to in diamond?

4

Why is diamond the hardest natural substance?

Due to its very rigid giant covalent structure

What are two uses of diamond?

<p>Drill tips and cutting tools</p> Signup and view all the answers

How many other atoms is a carbon atom covalently bonded to in graphite?

<p>3</p> Signup and view all the answers

What is a use of graphite and why can it be used for that?

<p>It is used as a lubricant because it has layers which can slide over each other.</p> Signup and view all the answers

Why is graphite the only non-metal that is a good conductor of electricity?

<p>It has free electrons.</p> Signup and view all the answers

Moles of a gas =

<p>Volume/24</p> Signup and view all the answers

1 mole of gas always occupies...

<p>24 dm cubed (at room temperature and pressure)</p> Signup and view all the answers

How to find the volume of a substance when you know its mass?

<p>Find molar mass for every element, divide by one of the molar masses then times by the mass, use the formula.</p> Signup and view all the answers

Volume =

<p>Mass/Mr x 24</p> Signup and view all the answers

What will be produced at the cathode if the metal ions are more reactive than hydrogen?

<p>Hydrogen</p> Signup and view all the answers

What will be produced at the cathode if the metal ions are less reactive than hydrogen?

<p>A solid layer of the metal</p> Signup and view all the answers

What will be produced at the anode if halide ions are present?

<p>Halogens</p> Signup and view all the answers

What will be produced at the anode if no halide ions are present?

<p>Oxygen</p> Signup and view all the answers

Electrolysis of sulfuric acid: cathode half equation

<p>2H+ + 2e- = H2</p> Signup and view all the answers

Electrolysis of sulfuric acid: anode half equation

<p>4OH- = O2 + 2H2O + 4e-</p> Signup and view all the answers

Electrolysis of sodium chloride: cathode half equation

<p>2H+ + 2e- = H2</p> Signup and view all the answers

Electrolysis of sodium chloride: anode half equation

<p>2Cl- = Cl2 + 2e-</p> Signup and view all the answers

Electrolysis of copper(II) sulfate: cathode half equation

<p>Cu2+ + 2e- = Cu</p> Signup and view all the answers

Electrolysis of copper(II) sulfate: anode half equation

<p>4OH- = O2 + 2H2O + 4e-</p> Signup and view all the answers

What is 1 faraday?

<p>96000 coulombs</p> Signup and view all the answers

What does 1 faraday contain?

<p>1 mole of electrons</p> Signup and view all the answers

Charge =

<p>Current x time</p> Signup and view all the answers

What are the 4 steps to find the mass of substance produced when time and current are given?

<p>Calculate the charge, divide the charge by 1 faraday (96000 coulombs), divide the number of faradays by the number of electrons in the half equation to find the number of moles, times the number of moles by the Mr = mass.</p> Signup and view all the answers

What are two ways ethanol can be produced?

<p>Ethene and steam, fermentation</p> Signup and view all the answers

What are two advantages of making ethanol by reacting ethene with steam?

<p>Fast and pure</p> Signup and view all the answers

What are two disadvantages of making ethanol by reacting ethene with steam?

<p>Non-renewable and expensive equipment needed</p> Signup and view all the answers

What are two raw materials for fermentation to make ethanol?

<p>Sugar (e.g. glucose) and yeast</p> Signup and view all the answers

What are two advantages of making ethanol by fermentation?

<p>Cheap and renewable</p> Signup and view all the answers

What are four disadvantages of making ethanol by fermentation?

<p>Ethanol must be distilled (as it isn't very concentrated), must be purified, slow, high labor costs</p> Signup and view all the answers

What is the method to turn ethanol back into ethene?

<p>Dehydration</p> Signup and view all the answers

How does the dehydration of ethene work?

<p>Water is removed from ethanol</p> Signup and view all the answers

Molar enthalpy change =

<p>Energy change/moles</p> Signup and view all the answers

What are three uses of Poly(chloroethene)?

<p>Clothes, pipes, insulating electrical cables</p> Signup and view all the answers

How are polyesters formed?

<p>A reaction between dicarboxylic acids and diols</p> Signup and view all the answers

How are polyamides formed?

<p>A reaction between dicarboxylic acids and diamines</p> Signup and view all the answers

What is an example of a polyamide?

<p>Nylon</p> Signup and view all the answers

What is another way polyamides are formed?

<p>Reaction between amino acids</p> Signup and view all the answers

What is brine?

<p>Sodium chloride solution</p> Signup and view all the answers

What equipment is used to electrolyse brine?

<p>Diaphragm cell</p> Signup and view all the answers

Cathode half equation for the electrolysis of brine

<p>2H+ + 2e- = H2</p> Signup and view all the answers

Anode half equation for the electrolysis of brine

<p>2Cl- = Cl2 + 2e-</p> Signup and view all the answers

What solution is left behind in the electrolysis of brine?

<p>Sodium hydroxide</p> Signup and view all the answers

What is the contact process used to make?

<p>Sulfuric acid</p> Signup and view all the answers

1st equation in the contact process

<p>S + O2 = SO2</p> Signup and view all the answers

2nd equation in the contact process

<p>2SO2 + O2 = 2SO3</p> Signup and view all the answers

3rd equation in the contact process

<p>SO3 + H2SO4 = H2S2O7</p> Signup and view all the answers

4th equation in the contact process

<p>H2S2O7 + H2O = 2H2SO4</p> Signup and view all the answers

What is H2S2O7?

<p>Oleum</p> Signup and view all the answers

What are three uses of sulfuric acid?

<p>Fertilisers (indirectly), detergents, paints (indirectly)</p> Signup and view all the answers

Flashcards

Giant Ionic Structure

A structure in which oppositely charged ions are held together by strong electrostatic forces forming a closely packed lattice.

Charge and Attraction

The strength of attraction between ions in a giant ionic structure increases with higher charges on the ions.

Diamond Structure

A very hard substance where each carbon atom is covalently bonded to four other carbon atoms, creating a rigid, tetrahedral structure.

Hardness of Diamond

The hardest naturally occurring substance due to its strong covalent bonds.

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Graphite Structure

A material where each carbon atom is covalently bonded to three other carbon atoms, forming layers that can slide over each other.

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Conductivity of Graphite

Graphite is a good conductor of electricity due to the presence of free electrons within its structure.

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Moles of Gas

The number of moles of a gas can be calculated by dividing the volume of the gas by 24 dm³ at room temperature and pressure.

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Molar Volume of Gas

At room temperature and pressure, one mole of any gas occupies a volume of 24 dm³.

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Calculating Gas Volume

The volume of a gas can be calculated using the formula: (mass / Mr) x 24.

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Electrolysis at the Cathode

During electrolysis, hydrogen gas is produced at the cathode when metal ions are more reactive than hydrogen. Less reactive metals form a solid metal layer.

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Electrolysis at the Anode

During electrolysis, if halide ions are present, halides are produced at the anode. If not, oxygen is produced.

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Electrolysis of H⁺

The half equation for the production of hydrogen gas at the cathode during electrolysis is: 2H⁺ + 2e⁻ = H₂.

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Electrolysis of OH⁻

The half equation for the production of oxygen gas at the anode during electrolysis is: 4OH⁻ = O₂ + 2H₂O + 4e⁻.

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Electrolysis of Cl⁻

The half equation for the production of chlorine gas at the anode during electrolysis is: 2Cl⁻ = Cl₂ + 2e⁻.

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Electrolysis of Cu²⁺

The half equation for the production of copper metal at the cathode during electrolysis is: Cu²⁺ + 2e⁻ = Cu.

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Faraday's Constant

One Faraday (F) is equal to 96,500 coulombs of charge, which corresponds to 1 mole of electrons.

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Calculating Charge

Charge can be calculated by multiplying the current (in amperes) by the time (in seconds).

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Mass from Electrolysis

The mass of a substance produced during electrolysis can be calculated by first determining the charge, then dividing by Faraday's constant to find moles, and finally using the molar mass (Mr) to find mass.

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Ethanol Production Methods

Ethanol can be produced through two methods: reacting ethene with steam or fermenting sugar using yeast.

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Ethene to Ethanol

Producing ethanol from ethene is fast and results in pure ethanol, but it requires expensive equipment and is non-renewable.

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Fermentation to Ethanol

Fermentation is a renewable and cheap method for producing ethanol, but it requires distillation and purification, making it slow and labor-intensive.

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Dehydration of Ethanol

The process of removing water from ethanol to revert it back into ethene.

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Molar Enthalpy Change

The energy change that occurs during a reaction divided by the number of moles involved.

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Uses of Poly(chloroethene)

Poly(chloroethene) is commonly used in products like clothing, pipes, and electrical cables.

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Polyester Formation

Polyesters are formed through the reaction between dicarboxylic acids and diols.

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Polyamide Formation

Polyamides can be produced from the reaction between dicarboxylic acids and diamines or from amino acids.

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Brine

A concentrated solution of sodium chloride, often used in industrial processes.

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Electrolysis of Brine

The electrolysis of brine produces hydrogen at the cathode (2H⁺ + 2e⁻ = H₂) and chlorine at the anode (2Cl⁻ = Cl₂ + 2e⁻).

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Sodium Hydroxide from Brine

The leftover solution after electrolysis of brine is sodium hydroxide (NaOH).

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Contact Process

The Contact Process is a method used to produce sulfuric acid, involving several distinct chemical reactions.

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Uses of Sulfuric Acid

Sulfuric acid is used extensively in the production of fertilizers, detergents, and paints.

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Study Notes

Giant Ionic Structures

  • Characterized by high melting and boiling points due to strong electrostatic attractions.
  • Structure consists of a closely packed lattice formed by the attraction between oppositely charged ions.
  • The strength of attraction increases with higher charges on the ions.

Diamond

  • Each carbon atom in diamond is covalently bonded to four other carbon atoms, forming a very rigid structure.
  • Diamond is the hardest natural substance due to its strong covalent bonding.

Uses of Diamond

  • Commonly used in drill tips and cutting tools.

Graphite

  • Each carbon atom in graphite is covalently bonded to three other carbon atoms.
  • Acts as a lubricant because it has layers that can slide over each other.
  • Good electrical conductor due to free electrons.

Gas Volumes and Moles

  • Moles of a gas can be calculated using the formula: volume/24.
  • At room temperature and pressure, one mole of gas occupies 24 dm³.

Calculating Volume

  • Volume can be calculated using the formula: mass/Mr x 24.
  • To find volume given mass, find the relative molecular mass (Mr) of each element involved.

Electrolysis

  • Hydrogen is produced at the cathode when metal ions are more reactive than hydrogen; less reactive metals produce a solid metal layer.
  • At the anode, if halide ions are present, halides are produced; if absent, oxygen is produced.

Electrolysis Half Equations

  • Electrolysis of sulfuric acid:
    • Cathode: 2H⁺ + 2e⁻ = H₂
    • Anode: 4OH⁻ = O₂ + 2H₂O + 4e⁻.
  • Electrolysis of sodium chloride:
    • Cathode: 2H⁺ + 2e⁻ = H₂
    • Anode: 2Cl⁻ = Cl₂ + 2e⁻.
  • Electrolysis of copper(II) sulfate:
    • Cathode: Cu²⁺ + 2e⁻ = Cu
    • Anode: 4OH⁻ = O₂ + 2H₂O + 4e⁻.

Faraday's Laws

  • 1 Faraday corresponds to a charge of 96,000 coulombs, equating to 1 mole of electrons.
  • Charge can be calculated as: current x time.

Finding Mass from Electrolysis

  • Steps to find mass of substance produced: calculate charge, divide charge by 1 Faraday, find moles from half equation, then calculate mass using moles and Mr.

Ethanol Production

  • Two methods to produce ethanol: reacting ethene and steam, or fermentation using sugar and yeast.
  • Producing ethanol from ethene is fast and pure but has disadvantages such as being non-renewable and requiring expensive equipment.
  • Fermentation is cheap and renewable, but ethanol needs distillation and purification, making it slow with high labor costs.

Dehydration Process

  • Dehydration of ethanol involves removing water to revert it into ethene.

Molar Enthalpy Change

  • Defined as energy change divided by the number of moles.

Uses of Poly(chloroethene)

  • Common applications include clothing, pipes, and insulating electrical cables.

Polymer Formation

  • Polyesters are formed from reactions between dicarboxylic acids and diols.
  • Polyamides are produced from reactions between dicarboxylic acids and diamines or from amino acids (an alternative method).

Brine and Electrolysis

  • Brine is a sodium chloride solution; electrolysis equipment used is known as a diaphragm cell.
  • Electrolysis of brine produces hydrogen at the cathode (2H⁺ + 2e⁻ = H₂) and chlorine at the anode (2Cl⁻ = Cl₂ + 2e⁻).
  • The leftover solution from this process is sodium hydroxide.

Contact Process for Sulfuric Acid

  • Used to produce sulfuric acid, following these equations:
    • S + O₂ = SO₂ (first step).
    • 2SO₂ + O₂ = 2SO₃ (second step).
    • SO₃ + H₂SO₄ = H₂S₂O₇ (third step).
    • H₂S₂O₇ + H₂O = 2H₂SO₄ (fourth step).
  • H₂S₂O₇ is also known as oleum.

Uses of Sulfuric Acid

  • Sulfuric acid is widely used in the production of fertilizers (indirectly), detergents, and paints (also indirectly).

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Test your knowledge of giant ionic structures with these flashcards focused on key concepts from Edexcel IGCSE Chemistry Paper 2. Learn about the properties and characteristics that define high melting and boiling points and the structural arrangement of ionic lattices. Perfect for revision and mastery of essential chemistry terms.

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