Worksheet Class 10 Chemistry 2

Case Study Question (HOTS type) for Class 10 Chemistry.

(Chemical Reactions, Acids–Bases–Salts, Metals–Non-metals):

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📝 Case Study – Chemistry (Class 10)

Read the passage carefully and answer the questions that follow:

Ramesh’s family uses aluminium utensils for cooking. Over time, he observed a dull layer forming on the surface of the vessels. His science teacher explained that aluminium reacts with oxygen in air to form a thin oxide layer, which actually protects the metal from further corrosion.
Ramesh also noticed that his grandmother often stored pickles in glass jars instead of metal containers. The reason was that acids present in pickles could react with metals and form harmful salts.
At school, Ramesh performed an experiment where he added dilute hydrochloric acid to sodium carbonate. He noticed brisk effervescence and the gas formed turned lime water milky. Later, when he exposed silver chloride to sunlight, it turned grey.

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Questions:

1. Why does aluminium vessel not corrode easily, even though it is reactive?
2. Why is it not advisable to store pickles in metal containers?
3. Write the balanced chemical equation for the reaction between sodium carbonate and dilute hydrochloric acid. Also, identify the gas evolved.
4. Which type of reaction is observed when silver chloride turns grey in sunlight? Write the equation.
5. Identify the common types of chemical reactions involved in the above passage and classify each.

Case Study Answers

Q1. Why does Aluminium vessel not corrode easily, even though it is reactive?

Aluminium reacts with oxygen in air to form a thin layer of Aluminium oxide (Al₂O₃), which is hard, impermeable, and protective.

This prevents further corrosion (self-protection).

Q2. Why is it not advisable to store pickles in metal containers?

Pickles contain acids (like acetic acid, citric acid).

Acids react with metals to form metal salts (sometimes toxic) and release hydrogen gas.

Therefore, pickles are stored in glass or plastic jars.

Q3. Write the balanced chemical equation for the reaction between sodium carbonate and dilute hydrochloric acid. Also, identify the gas evolved.

Na2CO3 + 2HCl --------> 2NaCl + H2O + CO2

It turns lime water milky due to formation of CaCO₃.

Q4. Which type of reaction is observed when silver chloride turns grey in sunlight? Write the equation.

Reaction:

2AgCl ----------------> 2Ag + Cl2

Q5. Identify the common types of chemical reactions involved in the above passage and classify each.

Situation Reaction type

Aluminium forms oxide layer Combination reaction + Corrosion prevention

Acid + Metal in pickles Displacement reaction

Sodium carbonate + HCl Double displacement + Neutralization reaction

Silver chloride in sunlight Photochemical decomposition