Chemical Reactions & Equations Unit Test Class 10 Science PDF Download

Time: 1 hour

M.M. 30

Attempt all questions.

• Question numbers 1 to 5 carry 1 mark each.
• Question numbers 6 to 8 carry 2 marks each.
• Question numbers 9 to 11 carry 3 marks each.
• Question number 12 & 13 carry 5 marks each.

Q1: Which of the following reactions is an endothermic reaction?    (1 Mark)
(a) Burning of coal.
(b)  Decomposition of vegetable matter into compost.
(c)  Process of respiration.
(d)  Decomposition of calcium carbonate to form quicklime and carbon dioxide. 

Q2: Which of the following reactions is BOTH a combination reaction and an oxidation reaction?   (1 Mark)
(a) CaO + H₂O → Ca(OH)₂
(b) 2Mg + O₂ → 2MgO
(c) Fe + CuSO₄ → FeSO₄ + Cu
(d) NaOH + HCl → NaCl + H₂O

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Q3: Why is respiration considered an exothermic reaction even though energy is not released suddenly?    (1 Mark)

Q4: The reaction Fe₂O₃ + 2Al → Al₂O₃ + 2Fe is an example of which type of reaction and why?   (1 Mark)

Q5: Why do silver articles become black after some time when exposed to air?    (1 Mark)

Q6: In the equations given below, state giving reasons, whether substances have been oxidised or reduced. (2 Marks)
(i) PbO + CO → Pb + CO₂
(ii) H₂S + Cl₂ → 2HCl + S

Q7: Can rancidity retard by storing foods away from the light?  (2 Marks)

Q8: What are the different ways can make more informative about the chemical equation?  (2 Marks)

Q9: The action of heat on ferrous sulphate is an example of a decomposition reaction.  (3 Marks) 

Q10:  When a green coloured crystalline salt ‘X’ is heated strongly in a dry test tube, it first loses water of crystallisation and then decomposes, giving a brown residue and two gases.

(a) Identify the salt ‘X’.
(b) Name the two gases evolved during the reaction.
(c) Write the balanced chemical equation for the reaction.  (3 Marks)

Q11: Write the balanced chemical equations for the following reactions  (3 Marks)
(a) Sodium carbonate on reaction with hydrochloric acid in equal molar concentrations gives sodium chloride and sodium hydrogencarbonate.
(b) Sodium hydrogencarbonate on reaction with hydrochloric acid gives sodium chloride, water and liberates carbon dioxide.
(c) Copper sulphate on treatment with potassium iodide precipitates cuprous iodide (CuI), liberates iodine gas and also forms potassium sulphate.

Q12: Identify the type of chemical reaction in the following statements and define each of them :
(i) Digestion of food in our body
(ii) Rusting of iron
(iii) Heating of manganese dioxide with aluminum powder.
(iv) Blue color of copper sulphate solution disappears when iron filings are added to it.
(v) Dilute hydrochloric acid is added to sodium hydroxide to form sodium chloride and water.  (5 Marks)

(a) Identify the substances that are oxidised and reduced in the reaction:
   Zn + CuSO₄ → ZnSO₄ + Cu

(b) Explain why this reaction does not occur when copper is placed in zinc sulphate solution.

(c) State the role of the reactivity series in predicting such reactions.

(d) Name the type of chemical reaction involved.

(e) Write one more example of a similar reaction.  (5 Marks)