Chemical Reactions Cheatsheet | Year 11 Chemistry
Having trouble keeping track of all the chemical equations you need to learn? Here is the complete list of all the chemical reactions year 11 students must know for the HSC.
In this article, we cover
- General chemical reactions
- Combustion reactions
- Reactions with acids
- Reactions with metals
- Redox reactions
- Photosynthesis and respiration
- Reactions in chemical tests
- Nuclear reactions
General Chemical Reactions
Synthesis reactions
Synthesis reaction involves the formation of a complex product from two simpler reactants.
A + B → AB
eg. 2C(s) + O2(g) → 2CO(g)
Decomposition reactions
Decomposition reactions are the opposite of synthesis reactions. A complex reactant decomposes into simpler products.
AB → A + B
eg. H2CO3(aq) → CO2(g) + H2O(l)
Precipitation reactions
Precipitation reactions occur when two aqueous solutions combine to form an insoluble salt.
AB(aq) + CD(aq) → AD(s) + CB(aq)
eg. AgNO3(aq) + KI(aq) → AgI(s) + KNO3(aq)
Combustion Reaction
Complete combustion of hydrocarbon
hydrocarbon + oxygen → carbon dioxide + water
eg. CH4(g) + 2O2(g) → CO2(g) + 2H2O(l)
Incomplete combustion of hydrocarbon
Incomplete combustion produces water and a combination of carbon soot and/or carbon monoxide.
hydrocarbon + oxygen → water + carbon soot + carbon monoxide
eg. 4CH4(g) + 5O2(g) → 8H2O(l) + 2C(s) + 2CO(g)
or
hydrocarbon + oxygen → water + carbon soot
eg. CH4(g) + O2(g) → 2H2O(l) + C(s)
or
hydrocarbon + oxygen → water + carbon monoxide
eg. 2CH4(g) + 3O2(g) → 4H2O(l) + 2CO(g)
Reactions with Acids
Acid / base reaction
Acids react with bases to form a salt and water. This is also referred to as a neutralisation reaction.
acid + base → water + salt
eg. HCl(aq) + NaOH(aq) → H2O(l) + NaCl(aq)
Acid / carbonate reaction
Acids react with metal carbonates to form water, carbon dioxide and a salt.
acid + carbonate → water + salt + carbon dioxide
eg. 2HCl(aq) + Na2CO3(aq) → H2O(l) + 2NaCl(aq) + CO2(g)
Acid / metal reaction
Metals react with dilute acids to form a metal salt and hydrogen gas.
acid + metal → salt + hydrogen gas
eg. Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
Reactions with Metals
Reaction of metal with liquid water
Generally, when metals react with liquid water, a metal hydroxide and hydrogen gas are produced
metal + liquid water → metal hydroxide + hydrogen gas
eg. Na(s) + H2O(l) → NaOH(aq) + H2(g)
Reaction of metal with gaseous water
Generally, when metals react with steam, a metal oxide and hydrogen gas is produced.
metal + steam → metal oxide + hydrogen gas
eg. Zn(s) + H2O(g) → ZnO(s) + H2(g)
Reaction of metal with oxygen
Metals react with oxygen gas in a combustion reaction to form metal oxides
metal + oxgen → metal oxide
2Mg(s) + O2(g) → 2MgO(s)
Redox Reactions
Redox reactions involve the transfer of electrons. One chemical species loses electrons and is oxidised while the other species gains electrons and is reduced.
Displacement reaction
Displacement reactions are a class of redox reactions and can be represented as a full equation:
2Al(s) + 6HCl(aq) → 2AlCl3(aq) + 3H2(g)
Net ionic equation
Displacement reactions can also be written as net ionic equations, where the spectator ions are removed
2Al(s) + 6H+(aq) → 2Al3+(aq) + 3H2(g)
Half equation
A redox reaction can be also represented using a pair half-equations to show the loss and gain of electrons
2Al(s) → 2Al3+(aq) + 6e– (oxidation)
6H+(aq) + 6e– →3H2(g) (reduction)
When writing half equations don’t forget to balance both the number of atoms and charge
Photosynthesis and Respiration
Photosynthesis
In the presence of sun light, carbon dioxide and water is converted to glucose and oxygen.
carbon dioxide + water + energy → glucose + oxygen
6CO2(g) + 6H2O(l) → C6H12O6(aq) + 6O2(g)
Cellular Respiration
Cellular respiration is the reverse of photosynthesis. Glucose and oxygen react to form water and carbon dioxide. This process releases energy.
glucose + oxygen → water + carbon dioxide + energy
C6H12O6(aq) + 6O2(g) → 6CO2(g) + 6H2O(l)
Reactions in Chemical Tests
Lime water test for carbon dioxide
A common way to test for the presence of carbon dioxide is by bubbling the gas through lime water Ca(OH)2 which is clear and colourless. If carbon dioxide is present, it will react with the lime water to form white calcium carbonate as a precipitate. The solution will turn a cloudy white.
calcium hydroxide + carbon dioxide → calcium carbonate + water
Ca(OH)2(aq) + CO2(g) → CaCO3(s) + H2O(l)
Hydrogen pop test
To test for the presence of hydrogen gas, hold a lit match above a sealed test tube. If a pop is heard, when the seal is removed, this indicates the presence of hydrogen gas.
2H2(g) + O2(g) → 2H2O(l)
Nuclear Reactions
Alpha decay
Alpha decay involves the emission of an alpha particle ^4_2He .
^A_ZX \rightarrow ^{A-4}_{Z-2} X + ^4_2He^{235}_{92}U \rightarrow ^{231}_{90}Th + ^4_2He
Beta decay
Beta decay involves the emission of a beta particle ^0_{-1}e .
^A_ZX \rightarrow ^{A}_{Z+1} X + ^0_{-1}e^-1^{14}_{12}C \rightarrow ^{14}_7N + ^0_{-1}e^-
Gamma decay
During gamma decay, an excited nucleus releases energy through the emission of a gamma ray.
^A_ZX^* \rightarrow ^A_ZX + \gamma^{137}_{56} Ba^* \rightarrow ^{137}_{56} Ba + \gamma
Written by Hee-Chan Jang
Hee-Chan is the author of Chemistry resources on Learnable. He loves teaching and helping students to "learn smarter", using his multidisciplinary knowledge of science and engineering. He is also currently completing his doctoral degree in mineral processing at The University of Sydney.
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