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Chemical misconceptions 57
Types of chemical
reaction
Target level
This probe is primarily designed for students in the 14–16 age range who have been introduced to the range of reaction types included. It may also be useful for checking the prior knowledge of students on post-16 courses.
Topics
Types of chemical reaction: displacement, neutralisation, oxidation, reduction, thermal decomposition.
Rationale
Students in the 14–16 year age range are expected to learn to recognise certain common types of reaction. Students are likely to come across a number of reactions in their studies. Recognising that a reaction is of a certain type can help the student fit the reaction into one of a limited number of classes. (See also the materials on Word equations for the 11–14 age range.) These ideas are discussed in Chapter 9 of the Teachers’ notes. During piloting, it was found that some students found the exercise difficult, but students recognised that it was useful and helped clarify concepts. Teachers reported that the probe was quick and simple to use, led to valuable discussion, and provided useful revision - enabling students to recognise patterns and connections ‘between seemingly disparate examples’.
Instructions
Each student requires a copy of the worksheet Types of chemical reaction. In the pilot some students found it difficult to explain the reasons for their classifications. Teachers may wish to ask some groups of students to just undertake the classification. Students may then be asked to explain the correct responses when the teacher goes through the examples. It should be emphasised that some reactions may be classified in several categories. (Note that oxidation and reduction are shown as separate classes.)
Resources
Student worksheet
- Types of chemical reaction
Feedback for students
A suggested answer sheet for teachers is provided. Teachers may wish to go through the answers for the example on the first page of the worksheet before their students attempt the rest of the exercise.
58 Types of chemical reaction
Types of chemical reaction –
answers
Example magnesium + steam → magnesium oxide + hydrogen Mg(s) + H 2 O(g) → MgO(s) + H 2 (g)
This is an example of an oxidation (magnesium is oxidised) and therefore also of a reduction (water is reduced).
It can also be seen as magnesium displacing hydrogen from water to form the oxide.
1. nitrogen + hydrogen → ammonia N 2 (g) + 3H 2 (g) → 2NH 3 (g)
This binary synthesis reaction an example of a reduction (nitrogen is reduced) and therefore also of an oxidation (hydrogen is oxidised).
2. sodium hydroxide + nitric acid → sodium nitrate + water NaOH(aq) + HNO 3 (aq) → NaNO 3 (aq) + H 2 O(l)
This is an example of a neutralisation reaction between an acid (nitric acid) and an alkali (sodium hydroxide).
3. copper carbonate + sulfuric acid → copper sulfate + water + carbon dioxide CuCO 3 (s) + H 2 SO 4 (aq) → CuSO 4 (aq) + H 2 O(l) + CO 2 (g)
This is an example of an acid-base reaction, but is not normally called a neutralisation.
4. sodium + water → sodium hydroxide + hydrogen 2Na(s) + 2H 2 O(l) → 2NaOH(aq) + H 2 (g)
This is an example of an oxidation (sodium is oxidised), and therefore also of a reduction (hydrogen from water is reduced).
This could also be considered as an example of a displacement reaction, with sodium displacing hydrogen.
5. zinc + copper sulfate → zinc sulfate + copper Zn(s) + CuSO 4 (aq) → ZnSO 4 (aq) + Cu(s)
This is an example of a displacement reaction - with zinc displacing copper from the salt.
This is also an example of an oxidation (zinc is oxidised) and therefore also of a reduction (copper is reduced).
6. copper carbonate → copper oxide + carbon dioxide CuCO 3 (s) → CuO(s) + CO 2 (g)
This reaction requires heating, and is an example of a thermal decomposition.
7. sodium bromide + chlorine → sodium chloride + bromine 2NaBr(aq) + Cl 2 (aq) → 2NaCl(aq) + Br 2 (aq)
This is an example of a displacement reaction - with chlorine displacing bromine in the salt.
It is also an example of an oxidation (bromide is oxidised to bromine) and a reduction (chlorine is reduced to chloride).
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Types of chemical reaction
Scientists classify chemical reactions into different types - such as oxidation and neutralisation.
This exercises provides the equations for a number of chemical reactions.
For each reaction you are given a word equation, and an equation using chemical symbols:
magnesium + steam → magnesium oxide + hydrogen
Mg(s) + H 2 O(g) → MgO(s) + H 2 (g)
You should try to classify each of the examples given.
✔ type of reaction
❑ displacement
❑ neutralisation
❑ oxidation
❑ reduction
❑ thermal decomposition
❑ none of the above
For each reaction tick (✔) the box, or boxes, that describe the type of reaction. Some of the reactions may be examples of more than one type of reaction.
Some of the reactions may only occur when energy is provided (as heat, or as electrical energy), but this is not shown in the questions.
Tick (✔) ‘none of the above’ if the reaction does not seem to fit any of the suggestions.
Explain why you have classified the reaction the way you have.
1. nitrogen + hydrogen → ammonia N 2 (g) + 3H 2 (g) → 2NH 3 (g)
✔ type of reaction I made this classification because:
❑ displacement ___________________________________________________________________
❑ neutralisation ___________________________________________________________________
❑ oxidation ___________________________________________________________________
❑ reduction ___________________________________________________________________
❑ thermal decomposition ___________________________________________________________________
❑ none of the above ___________________________________________________________________
2. sodium hydroxide + nitric acid → sodium nitrate + water NaOH(aq) + HNO 3 (aq) → NaNO 3 (aq) + H 2 O(l)
✔ type of reaction I made this classification because:
❑ displacement ___________________________________________________________________
❑ neutralisation ___________________________________________________________________
❑ oxidation ___________________________________________________________________
❑ reduction ___________________________________________________________________
❑ thermal decomposition ___________________________________________________________________
❑ none of the above ___________________________________________________________________
3. copper carbonate + sulfuric acid → copper sulfate + water + carbon dioxide CuCO 3 (s) + H 2 SO 4 (aq) → CuSO 4 (aq) + H 2 O(l) + CO 2 (g)
✔ type of reaction I made this classification because:
❑ displacement ___________________________________________________________________
❑ neutralisation ___________________________________________________________________
❑ oxidation ___________________________________________________________________
❑ reduction ___________________________________________________________________
❑ thermal decomposition ___________________________________________________________________
❑ none of the above ___________________________________________________________________
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7. sodium bromide + chlorine → sodium chloride + bromine 2NaBr(aq) + Cl 2 (aq) → 2NaCl(aq) + Br 2 (aq)
✔ type of reaction I made this classification because:
❑ displacement ___________________________________________________________________
❑ neutralisation ___________________________________________________________________
❑ oxidation ___________________________________________________________________
❑ reduction ___________________________________________________________________
❑ thermal decomposition ___________________________________________________________________
❑ none of the above ___________________________________________________________________
8. copper oxide + carbon → copper + carbon dioxide 2CuO(s) + C(s) → 2Cu(s) + CO 2 (g)
✔ type of reaction I made this classification because:
❑ displacement ___________________________________________________________________
❑ neutralisation ___________________________________________________________________
❑ oxidation ___________________________________________________________________
❑ reduction ___________________________________________________________________
❑ thermal decomposition ___________________________________________________________________
❑ none of the above ___________________________________________________________________
9. methane + oxygen → carbon dioxide + steam CH 4 (g) + 2O 2 (g) → CO 2 (g) + 2H 2 O(g)
✔ type of reaction I made this classification because:
❑ displacement ___________________________________________________________________
❑ neutralisation ___________________________________________________________________
❑ oxidation ___________________________________________________________________
❑ reduction ___________________________________________________________________
❑ thermal decomposition ___________________________________________________________________
❑ none of the above ___________________________________________________________________
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10. zinc + hydrochloric acid → zinc chloride + hydrogen Zn(s) + 2HCl(aq) → ZnCl 2 (aq) + H 2 (g)
✔ type of reaction I made this classification because:
❑ displacement ___________________________________________________________________
❑ neutralisation ___________________________________________________________________
❑ oxidation ___________________________________________________________________
❑ reduction ___________________________________________________________________
❑ thermal decomposition ___________________________________________________________________
❑ none of the above ___________________________________________________________________
11. sodium chloride → sodium + chlorine 2NaCl(l) → 2Na(l) + Cl 2 (g)
✔ type of reaction I made this classification because:
❑ displacement ___________________________________________________________________
❑ neutralisation ___________________________________________________________________
❑ oxidation ___________________________________________________________________
❑ reduction ___________________________________________________________________
❑ thermal decomposition ___________________________________________________________________
❑ none of the above ___________________________________________________________________
12. sodium nitrate → sodium nitrite + oxygen or sodium nitrate(V) → sodium nitrate(III) + oxygen
2NaNO 3 (s) → 2NaNO 2 (s) + O 2 (g)
✔ type of reaction I made this classification because:
❑ displacement ___________________________________________________________________
❑ neutralisation ___________________________________________________________________
❑ oxidation ___________________________________________________________________
❑ reduction ___________________________________________________________________
❑ thermal decomposition ___________________________________________________________________
❑ none of the above ___________________________________________________________________
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