Module 3 (Reactive Chemistry) Flashcards
Synthesis Reaction
Types of Reactions
A + B → AB
Decomposition Reaction (1)
Types of Reactions
AB → A + B
Metal carbonate →(heat) metal oxide + carbon dioxide
Single Displacement Reaction (3)
Types of Reactions
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
Double Displacement Reaction (2)
Types of Reactions
AB + CD → AD + CB
Neutralisation: Acid + base → salt + water
Precipitation: Aqueous solution + other aqueous solution → solid + another aqueous solution
Complete Combustion Reaction
Types of Reactions
Hydrocarbon + oxygen →(heat) carbon dioxide + water
Metal + oxygen →(heat) metal oxide
Corrosion: Metal + oxygen → metal oxide
Incomplete Combustion Reaction
Types of Reactions
Hydrocarbon + oxygen →(heat) carbon monoxide + water
Indicators of Chemical Change
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
Heat
Aboriginal and Torres Strait Islanders’ Detoxification of Food
Food is treated with fire to destroy toxins, kill germs, and improve texture.
Water
Aboriginal and Torres Strait Islanders’ Detoxification of Food
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.
Fermentation
Aboriginal and Torres Strait Islanders’ Detoxification of Food
Cycad fruit is stored for months in a moist environment. This allows the kernels to ferment, removing toxins.
Water
Reactivity of Metal
Metal and water generally react as the following:
- metal + water —> metal hydroxide + hydrogen gas
- metal + steam —> metal oxide + hydrogen gas
Dilute Acid
Reactivity of Metal
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.
Oxygen
Reactivity of Metal
Metal and oxygen generally react as the following:
- metal + oxygen —> metal oxide (combustion)
Metal Activity Series
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)
Ionisation Energy
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.
Electronegativity
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.
Atomic Radius
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.
Oxidation
Oxidation is loss of electrons.
In a galvanic reaction, a reactant is being oxidised if its standard potential is more negative.
Reduction
Reduction is gain of electrons.
In a galvanic reaction, a reactant is being reduced if its standard potential is less negative.
Oxidising Agent/Oxidant
Species that is reduced so that the other reactant can oxidise.
Reducting Agent/Reductant
Species that oxidises so that the other reactant can reduce.
Oxidation Number
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.
Using Standard Reduction Potentials
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)
Anodic Half Cell
Galvanic Cell
Electrode is anode (oxidises).
Positive charge building in electrolyte solution.
Cathodic Half Cell
Galvanic Cell
Electrode is cathode (reduces).
Negative charge building in electrolyte solution.
Calculating Cell Potential
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)
Temperature
Rate of Reaction
Proportional (high temperature = higher rate of reaction)
Increased kinetic energy, which makes particles more likely to collide with enough force to overcome activation energy.
Surface Area
Rate of Reaction
Proportional (high surface area = higher rate of reaction)
There is more surface area for particles to collide with, therefore increasing the frequency of collisions.
Concentration
Rate of Reaction
Proportional (higher concentration = higher rate of reaction)
Because there are more reactant particles within a fixed volume, therefore particles can collide more frequently.
Catalysts
Rate of Reaction
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
Activation Energy
The minimum energy needed by colliding particles to react upon collision.
Written as Ea.
Collision Theory
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.
Maxwell-Boltzmann Distribution Curve
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.
