Chapter 1: Chemical Reactions and Equations — Online MCQ Test
SCIENCE · Grade 10 · CBSE(NCERT)
Practice Chapter 1: Chemical Reactions and Equations with a free chapter-wise online MCQ test.
This chapter covers: Chemistry.
AI-generated questions from basic to board-exam level, with instant results and explanations.
Chapter 1: Chemical Reactions and Equations — Important Questions & Answers
What is the product formed when magnesium ribbon is burned in air?
- A. Magnesium chloride
- B. Magnesium hydroxide
- C. Magnesium oxide
- D. Magnesium sulphate
Answer: C. Magnesium oxide
When magnesium ribbon burns in oxygen, it gets converted to magnesium oxide (MgO), which appears as a white powder.
When magnesium ribbon burns in oxygen, it gets converted to magnesium oxide (MgO), which appears as a white powder.
Which symbol is used to represent a substance in aqueous state in a chemical equation?
- A. (g)
- B. (l)
- C. (s)
- D. (aq)
Answer: D. (aq)
The word aqueous (aq) is written if the reactant or product is present as a solution in water.
The word aqueous (aq) is written if the reactant or product is present as a solution in water.
What is the common name for calcium oxide?
- A. Slaked lime
- B. Quick lime
- C. Limestone
- D. Chalk
Answer: B. Quick lime
Calcium oxide (CaO) is commonly known as quick lime or lime.
Calcium oxide (CaO) is commonly known as quick lime or lime.
Which of the following is an example of a combination reaction?
- A. CaCO3 → CaO + CO2
- B. CaO + H2O → Ca(OH)2
- C. Fe + CuSO4 → FeSO4 + Cu
- D. 2AgCl → 2Ag + Cl2
Answer: B. CaO + H2O → Ca(OH)2
In a combination reaction, two or more reactants combine to form a single product. CaO and H2O combine to form Ca(OH)2.
In a combination reaction, two or more reactants combine to form a single product. CaO and H2O combine to form Ca(OH)2.
Why is a magnesium ribbon cleaned with sandpaper before burning in air?
- A. To make it longer
- B. To remove the layer of magnesium oxide from its surface
- C. To increase its mass
- D. To change its colour
Answer: B. To remove the layer of magnesium oxide from its surface
Magnesium reacts with atmospheric oxygen to form a stable MgO layer on its surface, which prevents further reaction. Cleaning removes this layer.
Magnesium reacts with atmospheric oxygen to form a stable MgO layer on its surface, which prevents further reaction. Cleaning removes this layer.
In the reaction Fe + CuSO4 → FeSO4 + Cu, why does the blue colour of copper sulphate solution fade?
- A. Iron dissolves completely in the solution
- B. Iron displaces copper from the solution as iron is more reactive
- C. Copper sulphate decomposes on contact with iron
- D. Water evaporates from the solution
Answer: B. Iron displaces copper from the solution as iron is more reactive
Iron is more reactive than copper, so it displaces copper from copper sulphate solution, reducing the concentration of blue copper sulphate ions.
Iron is more reactive than copper, so it displaces copper from copper sulphate solution, reducing the concentration of blue copper sulphate ions.
In the redox reaction ZnO + C → Zn + CO, which substance acts as the reducing agent?
- A. ZnO
- B. Zn
- C. CO
- D. C
Answer: D. C
Carbon (C) is oxidised to CO by gaining oxygen, while ZnO is reduced to Zn by losing oxygen. C acts as the reducing agent because it causes reduction of ZnO.
Carbon (C) is oxidised to CO by gaining oxygen, while ZnO is reduced to Zn by losing oxygen. C acts as the reducing agent because it causes reduction of ZnO.
In the balanced equation 3Fe + 4H2O → Fe3O4 + 4H2, which element is oxidised and which is reduced?
- A. Fe is reduced; H is oxidised
- B. Fe is oxidised; H is reduced
- C. O is oxidised; Fe is reduced
- D. H is oxidised; O is reduced
Answer: B. Fe is oxidised; H is reduced
Iron (Fe) gains oxygen to form Fe3O4, so it is oxidised. Hydrogen loses oxygen (water loses oxygen to give hydrogen gas), so hydrogen is reduced.
Iron (Fe) gains oxygen to form Fe3O4, so it is oxidised. Hydrogen loses oxygen (water loses oxygen to give hydrogen gas), so hydrogen is reduced.
Consider the reaction: CO(g) + 2H2(g) → CH3OH(l) carried out at 340 atm. What does the 340 atm indicate in the chemical equation?
- A. Temperature of the reaction
- B. Amount of catalyst used
- C. Pressure condition required for the reaction
- D. Speed of the reaction
Answer: C. Pressure condition required for the reaction
In chemical equations, conditions like temperature, pressure, and catalyst are written above or below the arrow. Here 340 atm indicates the pressure condition required for the reaction.
In chemical equations, conditions like temperature, pressure, and catalyst are written above or below the arrow. Here 340 atm indicates the pressure condition required for the reaction.
In the balanced equation 3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g), if 3 moles of iron react, how many moles of water are consumed and how many moles of hydrogen are produced?
- A. 3 moles of water; 3 moles of hydrogen
- B. 4 moles of water; 3 moles of hydrogen
- C. 4 moles of water; 4 moles of hydrogen
- D. 3 moles of water; 4 moles of hydrogen
Answer: C. 4 moles of water; 4 moles of hydrogen
From the balanced equation, 3 moles of Fe react with 4 moles of H2O to produce 4 moles of H2 and 1 mole of Fe3O4. The stoichiometric ratios are directly from the balanced equation.
From the balanced equation, 3 moles of Fe react with 4 moles of H2O to produce 4 moles of H2 and 1 mole of Fe3O4. The stoichiometric ratios are directly from the balanced equation.