Class 10 Science chapters: “Chemical Reactions and Equations” and “Acids, Bases and Salts”, including both conceptual and application-based types, suitable for practice and revision. Answers are also provided.
🧪 Chapter: Chemical Reactions and Equations
1. Define a chemical reaction. Give one example.
Answer: A chemical reaction is a process in which one or more substances (reactants) are converted into new substances (products).
Example:
2Mg + O2 -----------------> 2MgO
2. What is a balanced chemical equation? Why should chemical equations be balanced?
Answer:
A balanced chemical equation has equal number of atoms of each element on both sides.
It is balanced to obey the Law of Conservation of Mass.
3. Identify the type of chemical reaction:
Fe + CuSO4 ---------------> FeSO4 + Cu
Displacement reaction (Iron displaces copper from its salt).
4. What is a redox reaction? Give an example.
Answer:
A reaction in which both oxidation and reduction take place simultaneously.
Example:
Zn + CuSO4 ---------------> ZnSO4 + Cu
5. Why does a reddish-brown coating form on iron when it is left in open air? Write the equation.
Answer:
Due to formation of iron oxide (rust) by reaction with oxygen and moisture.
4Fe + 3O2 + 6H2O -----------> 4Fe(OH)3
🧪 Chapter: Acids, Bases and Salts
6. What happens when an acid reacts with a base? Write the reaction.
Answer:
Neutralization reaction occurs, forming salt and water.
HCl + NaOH --------------> NaCl + H2O
7. Which acid is present in the following?
a) Vinegar
b) Lemon
Answer:
a) Acetic acid
b) Citric acid
8. What is the chemical formula of baking soda? Mention one use.
Answer:
Formula: NaHCO₃
Use: Used in making baking powder for making cakes fluffy.
9. What is the pH range of acidic and basic substances?
Answer:
- Acidic: pH < 7
- Neutral: pH = 7
- Basic: pH > 7
10. Why does tooth enamel get damaged when pH in the mouth falls below 5.5?
Answer:
Tooth enamel (calcium phosphate) gets corroded by acids produced by bacterial action on food. Low pH leads to decay.
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