18 Questions
What is oxidation in a chemical reaction?
When a substance gains oxygen or loses hydrogen
Define reduction in a chemical reaction.
When a substance loses oxygen or gains hydrogen
Explain what happens in a redox reaction.
One reactant gets oxidised while the other gets reduced
Is magnesium oxidised or reduced in the reaction where it burns in air to form magnesium oxide?
Magnesium is oxidised
What is a common term used for the process of iron articles getting coated with a reddish brown powder over time?
Rusting
Give an example of a redox reaction mentioned in the text.
CuO + H2 → Cu + H2O
Explain what is meant by an exothermic reaction.
An exothermic reaction releases heat energy to the surroundings.
Why is respiration considered an exothermic reaction?
Respiration is considered exothermic because it releases energy in the form of heat as glucose is broken down to release energy for cellular functions.
Why are decomposition reactions called the opposite of combination reactions?
Decomposition reactions involve the breakdown of a single compound into simpler substances, while combination reactions involve the synthesis of a compound from simpler substances.
What is the difference between displacement and double displacement reactions?
Displacement reactions involve an element displacing another in a compound, while double displacement reactions involve the exchange of ions between two compounds.
Explain the concept of a precipitation reaction.
A precipitation reaction is a chemical reaction where an insoluble solid (precipitate) forms when two solutions are mixed.
What are the three forms of decomposition reactions based on the energy supplied?
Decomposition reactions can be classified into thermal decomposition (heat energy), photochemical decomposition (light energy), and electrolytic decomposition (electricity).
What is corrosion and how does it affect metals?
Corrosion is the process where metals are attacked by substances like moisture and acids, leading to damage. It causes the formation of coatings like black on silver and green on copper.
How does oxidation lead to rancidity in fats and oils?
When fats and oils are oxidized, they become rancid, changing their taste and smell.
What is the purpose of flushing bags of chips with gas such as nitrogen?
To prevent the chips from getting oxidized.
Explain the changes in the colour of copper sulphate solution when an iron nail is dipped in it.
The iron nail reacts with copper sulphate solution, leading to the displacement of copper by iron. This results in a change in color as iron(II) sulfate is formed.
Give an example of a double displacement reaction.
An example of a double displacement reaction is the reaction between sodium chloride and silver nitrate, which forms sodium nitrate and silver chloride.
Identify the substances that are oxidized and reduced in a chemical reaction.
In a chemical reaction, the substance that loses electrons is oxidized, while the substance that gains electrons is reduced.
Study Notes
Chemical Reactions
- Oxidation in a chemical reaction: the loss of one or more electrons by an atom, molecule, or ion.
- Reduction in a chemical reaction: the gain of one or more electrons by an atom, molecule, or ion.
Redox Reactions
- A redox reaction is a chemical reaction involving oxidation and reduction processes simultaneously.
- Example: combustion of magnesium to form magnesium oxide (Mg → MgO); magnesium is oxidized (loses electrons), and oxygen is reduced (gains electrons).
Corrosion and Rancidity
- Corrosion: the deterioration of metals, especially iron, due to oxidation reactions, resulting in a reddish-brown powder (rust).
- Oxidation leads to rancidity in fats and oils, spoiling their quality and flavor.
Reaction Types
- Exothermic reaction: a chemical reaction that releases heat energy, often accompanied by an increase in temperature.
- Respiration is considered an exothermic reaction as it releases energy in the form of heat.
- Decomposition reactions: the breakdown of a single compound into two or more simpler substances; opposite of combination reactions.
- Displacement reaction: a reaction where one element displaces another from a compound; e.g., Zn + CuSO₄ → ZnSO₄ + Cu.
- Double displacement reaction: a reaction where two compounds exchange partners; e.g., NaCl + AgNO₃ → NaNO₃ + AgCl.
- Precipitation reaction: a reaction where an insoluble solid (precipitate) forms from a solution; e.g., mixing NaCl and AgNO₃.
Decomposition Reactions
- Decomposition reactions can be classified into three types based on the energy supplied:
- Thermal decomposition: uses heat energy; e.g., 2H₂O → 2H₂ + O₂.
- Photodecomposition: uses light energy; e.g., 2H₂O + light → 2H₂ + O₂.
- Electrolytic decomposition: uses electric energy; e.g., 2H₂O → 2H₂ + O₂.
Miscellaneous
- Flushing bags of chips with gas (e.g., nitrogen) prevents oxidation and spoilage.
- The color change of copper sulphate solution when an iron nail is dipped in it is due to the formation of iron(II) sulphate, which has a greenish color.
- Example of a double displacement reaction: NaCl + AgNO₃ → NaNO₃ + AgCl.
- In a chemical reaction, the substances that are oxidized and reduced can be identified by tracking the loss and gain of electrons.
Test your knowledge of balancing chemical equations and identifying reaction types with this quiz. Practice writing balanced equations for reactions like calcium hydroxide + carbon dioxide producing calcium carbonate + water, and identifying reactions like double displacement or precipitation. Challenge yourself with equations involving potassium bromide, barium iodide, zinc carbonate, zinc oxide, and carbon dioxide.
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