Module 3 (Reactive Chemistry)

Question 1

Synthesis Reaction

Types of Reactions

Answer 1

A + B → AB

Question 2

Decomposition Reaction (1)

Types of Reactions

Answer 2

AB → A + B

Metal carbonate →(heat) metal oxide + carbon dioxide

Question 3

Single Displacement Reaction (3)

Types of Reactions

Answer 3

AB + C → AC + B

Active metal + acid → salt + hydrogen

Acid + metal carbonate → salt + carbon dioxide + water

Active metal + less active metal compound → less active metal + more active metal compound

Question 4

Double Displacement Reaction (2)

Types of Reactions

Answer 4

AB + CD → AD + CB

Neutralisation: Acid + base → salt + water

Precipitation: Aqueous solution + other aqueous solution → solid + another aqueous solution

Question 5

Complete Combustion Reaction

Types of Reactions

Answer 5

Hydrocarbon + oxygen →(heat) carbon dioxide + water

Metal + oxygen →(heat) metal oxide

Corrosion: Metal + oxygen → metal oxide

Question 6

Incomplete Combustion Reaction

Types of Reactions

Answer 6

Hydrocarbon + oxygen →(heat) carbon monoxide + water

Question 7

Indicators of Chemical Change

7

Answer 7

Change in colour

Formation of a gas (e.g. release of O2 in the hydrolysis of water )

Formation of a precipitate

Change in odour

Change in temperature (reactions can be either exothermic or endothermic - heat is absorbed into the system so the product has more heat than the reactants)

Burning caused by combustion

Emission of light

Question 8

Heat

Aboriginal and Torres Strait Islanders’ Detoxification of Food

Answer 8

Food is treated with fire to destroy toxins, kill germs, and improve texture.

Question 9

Water

Aboriginal and Torres Strait Islanders’ Detoxification of Food

Answer 9

Kernels of the cycad fruit are cut open and ground to increase surface area, then soaked in water. This lets the relatively soluble toxins wash out of the fruit, detoxifying it.

Question 10

Fermentation

Aboriginal and Torres Strait Islanders’ Detoxification of Food

Answer 10

Cycad fruit is stored for months in a moist environment. This allows the kernels to ferment, removing toxins.

Question 11

Water

Reactivity of Metal

Answer 11

Metal and water generally react as the following:

• metal + water —> metal hydroxide + hydrogen gas
• metal + steam —> metal oxide + hydrogen gas

Question 12

Dilute Acid

Reactivity of Metal

Answer 12

Metal and common dilute acids generally react as the following:

• metal + acid —> salt + hydrogen gas

Metals that do not react with water may react with acid as it is a slightly more reactive substance due to the ease of displacement of hydrogen ions.

Question 13

Oxygen

Reactivity of Metal

Answer 13

Metal and oxygen generally react as the following:

• metal + oxygen —> metal oxide (combustion)

Question 14

Metal Activity Series

Answer 14

Higher metal reactivity is due to lower electronegativity (more likely to lose electrons), which means it’s more likely to oxidise.

Please (Potassium)
Stop (Sodium)
Calling (Calcium)
Me (Magnesium)
A (Aluminium)
Careless (Carbon)
Zebra (Zinc)
Instead (Iron)
Try (Tin)
Learning (Lead)
How (Hydrogen)
Copper (Copper)
Saves (Silver)
Gold (Gold)

Question 15

Ionisation Energy

Answer 15

The amount of energy it takes to remove an electron from an atom.

The first electron to be removed from the atom has the lowest ionisation energy because it is on the outermost shell (the valence shell): its distance from the nucleus reduces the effect of core charge on keeping it attracted to the nucleus, therefore it is easiest to remove.

Ionisation energy will increase with each electron removed as the core charge increases and decreasing shells make electrons closer to the nucleus.

Increases across the period: Stronger core charge has stronger attraction wit the electrons.
Decreases down the group: Atomic radius increases down the group, meaning valence electrons become increasingly distanced from the nucleus.

Question 16

Electronegativity

Answer 16

The ability of an atom to attract electrons towards itself.

Valence electrons are more strongly attracted to the nucleus in atoms with greater electronegativity than in atoms with weaker electronegativity.

Increases across the period: Atomic number increases, strengthening core charge (ability to hold electrons).
Decreases down the group: Atomic radius increases, reducing core charge.

Question 17

Atomic Radius

Answer 17

Decreases across the period: Increasing core charge attracts electrons more strongly.
Increases down the group: Increase in electron shells move valence electrons further from the nucleus.

Question 18

Oxidation

Answer 18

Oxidation is loss of electrons.

In a galvanic reaction, a reactant is being oxidised if its standard potential is more negative.

Question 19

Reduction

Answer 19

Reduction is gain of electrons.

In a galvanic reaction, a reactant is being reduced if its standard potential is less negative.

Question 20

Oxidising Agent/Oxidant

Answer 20

Species that is reduced so that the other reactant can oxidise.

Question 21

Reducting Agent/Reductant

Answer 21

Species that oxidises so that the other reactant can reduce.

Question 22

Oxidation Number

Answer 22

Oxidation numbers (or oxidation states) are used to keep track of the movement of electrons in a chemical reaction equation. If there is a change, a redox reaction is occurring.

They occur accordingly:

• A naturally occurring atom has the oxidation number 0.
• Monoatomic ions have oxidation numbers equivalent to their charge.
• When combined with other metals, alkali metals always have oxidation number +1.
• When combined with other metals, alkaline earth metals always have oxidation number +2.
• Fluorine has the oxidation number -1.
• Hydrogen has the oxidation number +1.
• Oxygen has the oxidation number -2, except in peroxides.
• Halogens (Cl, Br, I) have the oxidation number -1.

The sum of the oxidation numbers in a neutral compound is 0, except in polyatomic ions where it is the charge of the ion.

Question 23

Using Standard Reduction Potentials

Answer 23

Can be used to form the half equations of a redox reaction. The higher up on the list, the more likely the reaction is to oxidise, though it must be reversed in the order displayed.

More positive equation is the cathode (will reduce)
More negative equation is the anode (will oxidise)

Question 24

Anodic Half Cell

Galvanic Cell

Answer 24

Electrode is anode (oxidises).

Positive charge building in electrolyte solution.

Question 25

Cathodic Half Cell

Galvanic Cell

Answer 25

Electrode is cathode (reduces).

Negative charge building in electrolyte solution.

Question 26

Calculating Cell Potential

Answer 26

E(cell) = E(cathode) - E(anode)

Positive cell potential: spontaneous reaction; spontaneous flow of electrons from anode to cathode.
Negative cell potential: non-spontaneous reaction; the only way to make electrons flow from anode to cathode is to supply electrical energy (electrolysis)

Question 27

Temperature

Rate of Reaction

Answer 27

Proportional (high temperature = higher rate of reaction)

Increased kinetic energy, which makes particles more likely to collide with enough force to overcome activation energy.

Question 28

Surface Area

Rate of Reaction

Answer 28

Proportional (high surface area = higher rate of reaction)

There is more surface area for particles to collide with, therefore increasing the frequency of collisions.

Question 29

Concentration

Rate of Reaction

Answer 29

Proportional (higher concentration = higher rate of reaction)

Because there are more reactant particles within a fixed volume, therefore particles can collide more frequently.

Question 30

Catalysts

Rate of Reaction

Answer 30

Introduced catalyst = higher rate of reaction

Catalysts lower the activation energy required for particles to collide successfully. So particles can react at lower temperatures, allowing them to react more immediately without having to wait until there is enough heat for them to collide successfully

Question 31

Activation Energy

Answer 31

The minimum energy needed by colliding particles to react upon collision.

Written as Ea.

Question 32

Collision Theory

Answer 32

In order to react when they collide, particles need a sufficient amount of kinetic energy to overcome the activation energy barrier. If they do not have enough energy and do not have the correct orientation, the particles will bounce apart unchanged after the collision.

Catalysts catalyse reactions by lowering the activation energy so that particles can collide with less kinetic energy but still successfully react.

Question 33

Maxwell-Boltzmann Distribution Curve

Answer 33

Shows that particles in a substance have a range of kinetic energies at any particular temperature. Most of the particles have similar kinetic energies, shown as the peak of the graph, however some particles will have a higher energy (the right side of the graph) or lower energy (the left side of the graph).

Less particles have high energy at any particular temperature compared to having low energy. This means that in a reaction, only a small proportion of particles will have enough energy to overcome activation energy and successfully collide with another reactant particle.

Increasing the temperature of the system raises the kinetic energy of all reactant particles involved, thus causing more particles to have enough energy to react.