Chemical Reactions & Equations: Class 10 Previous Year Questions

Chemical Reactions & Equations questions asked in CBSE board exams

Repeated questions first. Open the free app to see each question as it appeared in the paper, with its marking scheme.

1. (i) AgNO3 + NaCl · NaNO3 + AgCl (ii)K2SO4 + BaCl2 · ·BaSO4 + 2KCl Which of the following options clearly describes both the reactions ? (A) (i) is double displacement, (ii) is displacement reaction. (B) Both, (i) and (i) are displacement reactions and precipit…
   Board 20261 markMCQ
2. (a) Name the substance oxidised and reduced in the following reaction : ZnO + C- ·Zn+CO (b) Balance the following chemical reaction : Pb(NO3)2 + KI··> PbI2 + KNO3 (c) Give one example each of electrolytic decomposition and decomposition by sunlight.
   Board 20262 marksshort answer
3. Which of the following are combination reactions ? 1 (i) 2KClO3 ⎯→ ⎯ 2KCl + 3O2 (ii) MgO + H2O ⎯→ ⎯ Mg(OH)2 (iii) 4Al + 3O2 ⎯→ ⎯ 2Al2O3 (iv) Zn + FeSO4 ⎯→ ⎯ ZnSO4 + Fe Options : (A) (i) and (iii) (B) (iii) and (iv) (C) (ii) and (iv) (D) (ii) and (iii)
   Board 20261 markMCQ
4. (a) (i) Define the term decomposition reaction. Write one chemical equation each for decomposition reaction where energy is supplied in the form of heat, light or electricity. (ii) Decomposition of vegetable matter into compost is considered an exothermic reac…
   Board 20253 marksshort answer
5. Electrolysis of water is a decomposition reaction. The mass ratio (MH : MO) of hydrogen and oxygen gases liberated at the electrodes during electrolysis of water is : (A) 8 : 1 (B) 2 : 1 (C) 1 : 2 (D) 1 :
   Board 20251 markMCQ
6. The metals obtained from their molten chlorides by the process of electrolytic reduction are : (A) Gold and silver (B) Calcium and magnesium (C) Aluminium and silver (D) Sodium and iron
   Board 20251 markMCQ
7. Name the type of chemical reaction in which calcium oxide reacts with water. Justify your answer by giving balanced chemical equation for the chemical reaction.
   Board 20242 marksshort answer
8. It is observed that Calcium on reaction with water floats on its surface. product of this reaction reacts with Carbon dioxide gas ? Write a balanced chemical equation for the reaction.
   Board 20243 marksshort answer
9. (a) ·No precipitation reaction can occur without exchange of ions between the two reactants." Justify this statement giving a balanced chemical equation for the reaction. OR (b) Giving one example of each, differentiate between a displacement reaction and a do…
   Board 20242 marksshort answer
10. Write one chemical equation each for the chemical reaction in which the following have taken place : (i) Change in colour (ii) Change in temperature (ii) Formation of precipitate Mention colour change/temperature change (rise/fall)/compound precipitated along …
    Board 20243 marksshort answer
11. When 2 mL of sodium hydroxide solution is added to few pieces of granulated zinc in a test tube and then warmed, the reaction that occurs can be written in the form of a balanced chemical equation as : (a) NaOH + Zn ·NaZnO2 + H2O (b) 2NaOH + Zn · Na2ZnO2 + H2 …
    Board 20241 markMCQ
12. Select from the following a decomposition reaction in which source of energy for decomposition is light : (a) 2FeSO4 ·Fe2O3 + SO2 + SO3 (b) 2H20 · 2H2 + 02 (c) 2AgBr · 2Ag + Br2 (d) CaCO3 -· CaO + CO2 3. (a) (b) 3 (c) (d) 4. : / (i) () le e (l) (a) (i) (ii) (b…
    Board 20241 markMCQ
13. MnO2 + 4HCl · MnCl2 + 2H2O + Cl2 The reaction given above is a redox reaction because in this case : (a) MnO2 is oxidised and HCl is reduced. (b) HC1 is oxidised. (c) MnO2 is reduced. (d) MnO, is reduced and HCl is oxidised. 8. (a) (i) 3 (ii) (b) ( (i) (iv) (c…
    Board 20241 markMCQ
14. Select from the following a process in which a combination reaction is involved : (A) Black and White photography (B) Burning of coal (C· Burning of methane (D) Digestion of food
    Board 20241 markMCQ
15. (a) Identify the reducing agent in the following reactions : (i) 4NH, + 502 · 4NO + 6H,0 (ii) H,O +F, ·HF + HOF (iii) Fe,O; + 3CO · 2Fe + 3CO2 (iv) 2H, + O, · 2H,0 (b) Define a redox reaction in terms of gain or loss of oxygen.
    Board 20233 marksshort answer
16. Mm (H$) Mm`Zm {S>e (I) hmoZo dmbr amgm`{ZH$ A{^{H«$`m Ho$ àH$ma H$m Zm_ VWm Bg A{^{H«$`m H$m amgm`{ZH$ g_rH$aU {b{IE & (J) Bg A{^{H«$`m H$m EH$ Cn`moJ {b{IE & Bgr CÔoí` Ho$ {bE Cn`moJ {H$E OmZo dmbo {H$gr AÝ` agm`Z H$m Zm_ {b{IE &
    Board 20233 marksshort answer
17. (a) What is observed when aqueous solutions of potassium iodide and lead nitrate are mixed together ? Name the type of reaction and write the chemical equation for the reaction that occurs. 2 OR (b) When copper powder is heated in a watch glass, a black substa…
    Board 20232 marksshort answer
18. The emission of brown fumes in the given experimental set-up is due to 2. Brown fumcs Lead nitrate Burner (a) thermal decomposition of lead nitrate which produces brown fumes of nitrogen dioxide. (b) thermal decomposition of lead nitrate which produces brown f…
    Board 20231 markMCQ
19. H 3 H 1. Which of the following is an example of endothermic process ? (a) Formation of slaked lime (b) Decomposition of vegetable matter into compost (c) Dissolution of ammonium chloride in water (d) Digestion of food in our body H 4 H 2. Xr J`r àm`mo{JH$ ì`d…
    Board 20231 markMCQ
20. pp ( ) 2 The ratio (x:y) of reactants Fe and H2O in the given balanced chemical equation is . xFe(s) + yH2O(g) → Fe3O4 (s) + 4H2 (g) a) x:y = 2:3 b) x:y = 3:4 c) x:y = 1:4 d) x:y = 4:1 1 U
    CBSE practice 2023-241 markvery short

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